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The Coronavirus Disease 2019 (COVID-19) is an ongoing global pandemic and wearing face mask is recommended across the globe to break the transmission chain of infection. The masks available in the market are of different types and materials and tend to alter the voice characteristics of the speaker. This can therefore impair optimal communication and the present study is a systematic review exploring the effect of various masks on voice production parameters. Systematic review. The titles and abstracts screening was carried out for the inclusion of articles using eight electronic databases spanning the period from 1st January 2020 to 30th April 2021. 10 articles (8 published & 2 in pre-print) that met the inclusion criteria were considered for this systematic review and the pooled age range was 18 –69 years. Three primary studies from the USA, 2 each from Australia & Italy, one each from Brazil, China, and Germany were found to have investigated the influence of wearing N95, KN95, surgical and fabric masks on voice related measures. The users significantly reported vocal fatigue, discomfort, and also perceived voice problems. Attenuation of speech sound amplitude was highest for the transparent mask followed by cloth mask, N95, KN95, and surgical mask. The World Health Organization (WHO) has been repeatedly endorsing the need to use a face mask in the current COVID-19 pandemic. However, for an unintruded voice production, the surgical mask is recommended for everyone, including healthcare professionals when they are not in close contact with patients, and not involved in aerosol-generating procedures. For teachers, doing direct teaching (offline classes), 'surgical mask' can reduce the vocal load of teachers, smoothen the teacher-student interaction and thereby facilitate better learning by the students. Additionally, it would be useful to protect oneself from the risk of developing voice problems by following standard vocal healthcare tips. [ABSTRACT FROM AUTHOR]

The objective of this study was to compare phonetic outcomes of TOETVA with those of conventional transcervical thyroidectomy(OPEN). Retrospective chart review of total 61 patients who received thyroidectomy through OPEN (n = 34) or TOETVA (n = 27) approach in single tertiary center were enrolled. There were significant differences in F0 between the two groups and there were significant changes from different time points within each group in jitter for vowel /i/. Aerodynamically, there were significant differences in mean sound pressure level for vowel /a/ and mean sound pressure level, mean air pressure, and aerodynamic resistance for syllable /pa/ between the two groups. In subjective VHI evaluations, there were no significant differences between the two groups. This study is significant in that it has investigated voices of patients with TOETVA. Results of this study are expected to be useful for voice evaluation, treatment, and prevention in the future. 3 [ABSTRACT FROM AUTHOR]

Since their development at the end of the 50s, panel methods were widely used for the fast simulation of aerospace objects reentry. Although improvements were proposed for the continuum regime formulations, the bridging functions usually employed in the transitional regime did not go through major changes since then. With the current interest in designing Very Low Earth Orbit satellites and more efficient reentry vehicles, a greater level of preciseness is now required for the fast computation of the aerodynamic and aerothermodynamic wall quantities in rarefied regime. In this context, this paper presents a new approach to build Machine Learning based surrogates going from the choice of the design variables and the Design of Experiments, to the models training and evaluation. Hence, kriging and Artificial Neural Networks are respectively trained to predict the pressure and heat flux stagnation coefficients, and the pressure, friction and heat flux coefficient distributions in the rarefied portion of any aerodynamic shape's reentry. • New reduced models for the wall quantities in hypersonic rarefied conditions. • Kriging models for the stagnation heat flux and pressure coefficients. • Neural networks for the friction, heat flux and pressure coefficient distributions. • A thorough and challenging validation of the models has been carried out. • A more precise and generic alternative to classic panel methods. [ABSTRACT FROM AUTHOR]

• Presenting aero-thermodynamic responses MD-FG sector disk in supersonic airflow, for the first time. • Presenting quasi-3D new refined theory to present the displacement fields of the MD-FG sector disk in higher-order shapes. • Presenting flutter and frequency response of the temperature-dependent MD-FG sector disk for different parameters. • Presenting the GDQ method to solve the governing equations of the current higher-order structure. • Presenting deep neural networks model with related parameters to simulate the current applicable structure with low computational cost. Composite sector disks have extensive applications in aerospace industries, particularly when exposed to challenging conditions such as supersonic airflow and thermal environments. These applications leverage the superior properties of composite materials, including high strength-to-weight ratios, enhanced durability, and excellent thermal resistance, to meet the stringent requirements of aerospace operations. Multi-directional functionally graded (MD-FG) materials due to high-temperature resistance and other amazing properties in each direction have gotten plenty of attention recently. So, in this research, a thermoelasticity solution has been presented to study fundamental frequency traits of an MD-FG sector disk in supersonic airflow via both mathematics simulation and deep neural networks technique. For obtaining exact displacement fields, along with defining the changes of transverse shear strains along the system's thickness, the refined zigzag hypothesis is utilized. For obtaining the temperature-dependent equations, heat conduction relation and thermal boundary conditions of the MD-FG structure are presented. A coupled quasi-3D new refined theory (Q3D-NRT) and generalized differential quadrature method (GDQM) are presented for obtaining and solving the partial differential equations in the time-displacement domain. After obtaining the mathematics results, appropriate datasets are made for testing, training, and validation of the deep neural networks technique. Finally, the results have shown that aerodynamic pressure, temperature changes, Mach number, free stream speed, and air yaw angle have a major role in the stability/instability analyses of the thermally affected MD-FG sector disk in supersonic airflow. As an amazing outcome, increasing the sector angle, FG indexes, and temperature change lead to the reduction of the critical Mach number, and aerodynamic pressure associated with the flutter phenomenon. [ABSTRACT FROM AUTHOR]

Free-running model test is one of the main test methods to study the performance of ships. In this study, a free-running test model was designed based on the planing trimaran model. The test model has a propulsion system and a data acquisition system, which can complete the functions of remote control, collecting thrust value and speed data and remote transmission data. Two kinds of wings were added to the test model, including the canard wing and the main wing. The test mainly studied the influence of the aerodynamic lift generated by the canard and the main wing on the rapidity of the planing trimaran. The test results show that with the increase of speed, the wing structure can produce considerable aerodynamic lift, and the purpose of reducing drag can be achieved by changing the pitch of the hull and lifting the hull. The test results verify the feasibility of using aerodynamic lift to improve the rapidity of high-speed planing craft. The combination of canard and main wing at the optimal attack angle can reduce hull resistance by 16.5 %. [ABSTRACT FROM AUTHOR]

Semioccluded vocal tract (SOVT) exercises are routinely included in many voice therapy programs because they have been shown to improve acoustic, aerodynamic, and patient-reported voice outcomes. One limitation of the traditional SOVT exercise is that the nature of phonation through straws or semioccluded oral postures allows only for single phoneme production. A variably occluded facemask (VOFM) allows for use of articulated connected speech beyond the production of single phonemes, while still providing occlusion and, presumably, the vocal efficiency benefits that arise from it. This study reports on the effect of time duration of phonation with a variably occluded facemask on voice outcomes in patients with voice disorders. Prospective, randomized cohort study. Fifteen patients with voice disorders phonated for 5 minutes through a VOFM with diameter openings of 3.2, 6.4, and 9.6 mm. Acoustic and aerodynamic voice measures were collected before and after each occlusion trial. These results were compared to a historical patient group that received the same phonation training for 2 minutes. Positive effect sizes were found for acoustic and aerodynamic improvements for all patients for at least one occlusion diameter. Effect sizes for aerodynamic outcomes were greater in the 5-minute conditions for both the 9.6- and 6.4-mm occlusions than the 2-minute condition. Effect sizes for acoustic outcomes were greater in the 5 minute than 2-minute trial for the 9.6- and 6.4-mm occlusion diameter, but greater in the 2 minute than 5-minute trial for 3.2-mm diameter. This study provides evidence that all three occlusion sizes may elicit beneficial changes for different patients; however, 5 minutes of phonation into a facemask with end occlusion of 6.4-mm diameter results in improved acoustic and aerodynamic voice outcomes for many patients with voice disorders. Future studies should further explore phonatory physiologic changes of the VOFM in a larger sample of patients and translate effects into clinical treatment for patients with voice disorders. [ABSTRACT FROM AUTHOR]

Lung cancer is the leading cause of cancer death. Many studies have shown the beneficial effects of Atorvastatin in decreasing the mortality risk and improving survival among patients with lung cancer. This research paper focuses on improving AVT cytotoxic activity and cellular uptake by developing mannitol microcarriers as a promising drug delivery system for lung cancer treatment and, studying the impact of improving inhalation deposition on the delivery and Dry Powder formulations efficiency. The AVT loaded mannitol (AM) microparticles (AVT-AM) formulation was prepared by spray drying and characterized for its physicochemical properties and aerodynamic deposition. The results revealed that the AVT-AM formulation has good flow properties and aerosol deposition with a particle size of 3418 nm ± 26.86. The formulation was also assessed in vitro for cytotoxicity effects (proliferation, apoptosis, and cell cycle progression) on A549 human lung adenocarcinoma. Compared with free AVT, the AVT-AM formulation has significantly higher cellular uptake and anti-cancer properties by disrupting cell cycle progression via either apoptosis or cell cycle arrest in the G2/M phase. This study shows that AVT loaded mannitol microcarriers may provide a potentially effective and sustained pulmonary drug delivery for lung cancer treatment. [ABSTRACT FROM AUTHOR]

The purpose of this study was to characterize the acoustic and aerodynamics of the voice of young men with prelingual deafness after cochlear implantation (CI) to provide a theoretical basis for their rehabilitation after CI. The CI group included 17 young men with prelingual deafness who implanted cochlear at 18–24 years old. The control group included 17 normally hearing young men at the same age. The 10-item Voice Handicap Index, acoustic parameters, and aerodynamic parameters were evaluated. For the acoustic parameters, the F0, SDF0, and Jitter of the CI group were higher than those of the Control group, and these differences were statistically significant. Additionally, The difference in mean shimmer and mean NHR values between the CI group and the Control group was not statistically significant For the aerodynamic parameters, the subglottal pressure and aerodynamic power of the CI group were significantly higher than those of the Control group, whereas the MPT was significantly shorter. Due to excessive stress on the laryngeal muscle and limited pneumo-phono-articulatory coordination, the young men in the CI group had a thin voice and poor voice control and muscle coordination, and they exhibited excessive laryngeal resistance. We propose that after CI, in addition to regular hearing and speech rehabilitation, voice training is also extremely important for prelingually deaf young men. [ABSTRACT FROM AUTHOR]

Mean flow rate (MFR) and laryngeal resistance (R L) are sensitive to changes in glottal configuration and biomechanics. There is little reported on aerodynamic parameters in children. We conducted a pilot study to evaluate MFR and R L measurement reliability in a pediatric population using labial and mechanical interruption methods. Thirty-nine subjects aged 4–17 performed 10 trials per method. For labial interruptions, subjects produced five labial plosives at a comfortable amplitude. For mechanical interruptions, subjects maintained a steady /α/ while a balloon valve interrupted their airflow five times for 250 milliseconds each. MFR was measured as the flow through the interruption device between interruptions. R L was calculated by dividing subglottal pressure (P s) by MFR. The primary outcome measures of this study were the coefficients of variation of MFR and R L. Paired t tests were used to compare each variable between the two methods. Pearson's correlation was used to analyze the relationship between each parameter and subject age. Mean P S (t(38) = 2.966, P < 0.01) and R L (t(38)=3.563, P < 0.01) were higher for labial interruptions while mean MFR (t(38) = −2.036, P < 0.05) was lower. Intrasubject coefficients of variation were higher for the labial technique for both MFR (t(38) = 4.939, P < 0.001) and R L (t(38) = 3.439, P < 0.01) while there was no difference in P S variability (P = 0.260). Mean MFR and R L were related to age for both the labial (MFR: r = 0.588, P < 0.001; R L : r = −0.468, p = 0.003) and mechanical trials (MFR: r = 0.534, P < 0.001; R L : r = −0.496, P = 0.001). The coefficients of variation for R L were negatively correlated with age for both labial (r = −0.415, P = 0.009) and mechanical trials (r = −0.471, P = 0.002). MFR was only correlated in the labial trials (r = −0.514, P = 0.001) and P S was only correlated in the mechanical trials (r = −0.519, P = 0.001). Differences in means and intrasubject variation are likely due to differences in task and measurement timing. Precision of MFR and R L measurement in pediatric subjects was higher for mechanical interruption; further exploration of this method and its clinical utility is warranted. Measurement of aerodynamic parameters may be a useful addition to pediatric voice assessment. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the vocal changes in the Iranian pregnant women according to trimesters both objectively and subjectively. There were 93 pregnant women and 31 non-pregnant women participants in the study. Thirty-three of the 93 pregnant women were in their first trimester, 31 in their second trimester, and 29 in their third trimester of their pregnancies. Clinical data were collected from the acoustic measurements, aerodynamic assessment, video laryngoscopy examination, and the self-assessment of quality of life related to voice using the Persian Voice Handicap Index (VHI P). The analysis of variance (ANOVA) test and Kruskal–Wallis test were used for between-group comparisons of the data. Decreased maximum phonation time (MPT), increased S/Z ratio, increased VHI P -30 scores, and evidence of vocal fold edema were the parameters that differed significantly only in the third trimester. Acoustic analysis revealed that F0, jitter, shimmer, and noise-to-harmonics ratio (NHR) were not significant across the four groups. Results showed that decreased MPT, increased S/Z ratio, mild to moderate edema, and a deterioration of the VHI P -30 score noticeably occurred during the third trimester. The results suggest significant vocal changes toward less stable phonation during the third trimester of pregnancy. [ABSTRACT FROM AUTHOR]

The aerodynamic, heat transfer and film cooling characteristics of three tip configurations (including pressure-side partial squealer tip, suction-side partial squealer tip and cavity squealers tip) with cooling are evaluated on transonic turbine, and the effect of the jet and shroud motion are talked. The flow and heat transfer mechanisms of three cooled tip configurations are analyzed. Results show that both the jet and shroud motion alter the tip gap flow, which is found to have a different impact on the aerothermal and film cooling performances of three tip configurations. The addition of cooling significantly increases the overall heat transfer coefficient of the SS tip, but has a relatively small impact on that of the PS tip and Squealers tip. As a result, the total h ¯ of SS cooled tip is even increased by 9.0% compared to Squealers cooled tip. The shroud motion increases the film cooling effectiveness of PS cooled tip and Squealers cooled tip, but reduces that of SS cooled tip. Under the moving shroud condition, Squealers cooled tip have significant advantages in aerodynamic, heat transfer and film cooling performances compared to the other two cooled tip structures. [ABSTRACT FROM AUTHOR]

The present study evaluates and compares the performance matrix of a curved and flat solar air heater (SAH) under diverse environmental conditions using an experimentally validated numerical model. Firstly, the optimum curvature angle for curved SAH that offers optimum thermal performance (i.e. 25°) under wide range of parameters such as Reynolds numbers (2200–6000), mass flow rate (0.0172–0.0472 kg/sm2) and solar radiation inclination angle (0–60°) has been determined. The enhancement factor (i.e. N u c u r v e d / N u f l a t ) is in the range 1.5-2.2 which show that curved SAH is thermally much better than flat design. Secondly, the optimized curved SAH is then compared with flat design for 0–60° tilt angles θ , under tranquil and windy conditions (wind velocity range: 0.5–4 m/s), respectively. Under windy condition the heat loss from SAH to surrounding is lower for curved SAH at θ = 0°, 60° in windward, 30° in leeward and 30° in tranquil- condition in comparison to flat SAH. In the extreme case θ = 60° and wind speed of 4 m/s, the percentage change in average differential pressure coefficient Δ C P is about 2% higher for curved SAH under windward while it is about 19% less in leeward condition compared to flat SAH. Image 1036206 • Determined optimal curvature angle of curved solar air heater (SAH). • Thermal efficiency is maximum for curved SAH having 25° curvature angle. • Investigated thermal performance, environmental heat loss and aerodynamic characteristics of curved SAH vs. flat SAH. • Thermal performance of curved SAH is better than flat SAH. • Environmental heat loss is lower for flat SAH than curved SAH. [ABSTRACT FROM AUTHOR]

The aerodynamic and aeroacoustic behaviors of the Darrieus vertical axis wind turbine are very complicated. Hence, it is challenging to simulate the real flow behavior using the computational fluid dynamics approach. In the present study, the behavior of two different numerical techniques, Unsteady Reynolds Averaged Navier Stokes and Delayed Detached-Eddy Simulation (DDES), are compared to predict the aerodynamic and aeroacoustic performance. The DDES approach with the higher order scheme is used to investigate the noise mechanisms of Darrieus VAWT at several operating conditions. It is concluded that the dominant noise mechanism, when the turbine operates at low and high speed ratios, is a dipole noise, without any contribution from the monopole sound in the time averaged signal. Moreover, all the blade segments along the chord have a significant contribution to noise production. The leading edge segment is responsible for the noise reflects the load fluctuations by the variation of the effective angle of attack, flow blade relative velocity, and Blade vortex interaction. On the other hand, the rest of the blade segments reflect the load fluctuations by the massively separated flow at low speed ratio, while at high speed ratio it is as the same as the leading edge. [ABSTRACT FROM AUTHOR]

The aerodynamics of the glider with supersonic airfoil have been optimized numerically by combining the multi-island genetic algorithm (MIGA) with the simulated annealing (SA) methods. The corresponding results show that the improved hybrid MIGA-SA method can effectively solve the glider optimal design issues such as nonlinear, discontinuous, and multi-dimensional multimodal function etc. The glider optimal aerodynamic geometry can be quickly obtained by using of the hybrid MIGA-SA method under the conditions of huge design space and low calculating resource requirements. The optimized results have also indicated that the aerodynamic characteristics for the double curved airfoil are always superior to the hexagonal airfoil. The total length of wing span located closer to the constraint value can greatly increase the wing area, decrease wing load and benefit in gliding. The final optimal geometry can greatly extend the flight distance for the glider. These results could provide the reference data for designing the gliders with supersonic airfoil in aerodynamic geometry, control system as well as the structural optimal. [ABSTRACT FROM AUTHOR]

This paper investigates the feasibility of using four movable masses distributed in a plane to realize three-axis attitude stabilization. With the proposed distribution and moving the paired masses in the same or opposite direction simultaneously, aerodynamic torque or internal momentum exchange torque is acted on the spacecraft. Then the spacecraft is gradually stabilized under a three-phase control strategy. Each of the three control phases is designed based on optimal control, nonlinear and sliding mode control, respectively. The stability of the proposed controller is given. Furthermore, numerical simulation matches the analytical results presented in this paper. Results show that three-axis attitude stabilization is possible using only in-plane movable masses which weigh less than 10 percent of spacecraft mass. Finally, the proposed control system can be a viable alternative for three-axis attitude stabilization of spacecraft orbiting in low Earth orbit. [ABSTRACT FROM AUTHOR]

Abstract In order to optimize the large wind turbines operation in ice prone cold regions, it is important to better understand the ice accretion physics and its effects on aerodynamic performance and power production losses. This paper describes a case study of ice accretion on DU96-W-180 airfoil, which has been used for large wind turbine blades such as NREL 5 MW. Analysis has been carried out for glaze and rime ice conditions using icing tunnel experimental data and multiphase Computational Fluid Dynamics (CFD) based numerical approach. Results show a difference in profile surface roughness and heat fluxes during rime and glaze ice accretion process, which leads to a significant change in rate and shape of ice accretion. More complex ice shapes are observed in case of glaze ice conditions that affects the aerodynamic performance differently from rime ice conditions. Numerical results are compared with the experimental data, where a good agreement is found. Results show higher aerodynamic performance degradation for glaze ice conditions particularly at higher angles of attack. Highlights • Wind turbine operations in icing conditions. • Atmospheric ice accretion on DU96 airfoil. • Aerodynamics performance. • Comparison of experimental and multiphase CFD numerical simulations. • Comparison of aerodynamic characteristics of clean and iced DU96 profiles. [ABSTRACT FROM AUTHOR]

With the increase in the speed of metro trains, the aerodynamic effects caused by the train passing through the tunnel, especially the pressure change, will be significantly enhanced. This pressure will have a significant effect on the auxiliary facilities in the tunnel and the passengers in the carriage. Based on the sliding grid technique, Fluent software was used to simulate the aerodynamic performance of six trains passing through different shield transfer structures, and the influences of the shield cross-section area, length, and form on train aerodynamic performance were studied. The results show that when the cross-sectional area of the shield transfer structure increases from 42 m2 to 62 m2, the positive pressure peak P max on the train surface increases significantly, and the peak-to-peak value and positive pressure gradient peak in the large-section tunnel are increased by 20.50 % and 106.83 %, respectively; when the length of the shield transfer structure is increased from 80 m to 120 m, the positive pressure peak and pressure gradient peak in the large-section tunnel are increased by 22.53 % and 21.70 %, respectively; for constant cross-sectional area and ellipsoidal structural forms, the slanting structural form has a smaller train surface pressure amplitude as well as a smaller peak pressure and peak pressure gradient in a large-section tunnel. These findings will contribute to the design of shield transfer structure in subway and tunnel systems. [ABSTRACT FROM AUTHOR]

Highlights • IFSM is extended to the aerodynamic 3D flutter analysis of bridges. • The solution falls into the category of multi-mode and full-mode flutter analysis. • The convergence rate of the method is very high. • An optimal scheme is proposed for solving the flutter eigenvalue problem. • A simple technique is developed in order to handle different end conditions. Abstract The recently developed integrated finite strip method (IFSM) is extended to the aerodynamic flutter analysis of bridges under wind effects. The methodology is capable of performing a three-dimensional (3D) flutter analysis in the IFSM environment, and the solution falls into the category of both multi-mode and full-mode flutter analysis. Aerodynamic stiffness and damping matrices, as well as structural property matrices, are derived by IFSM. In addition, an optimal scheme is proposed for solving the flutter eigenvalue problem. Furthermore, a simple technique has been developed in order to handle different end boundary conditions. The proposed finite strip solution is very straightforward in terms of amount of input data, boundary conditions, modeling, and the flutter analysis process. Moreover, the convergence rate of the method is very high due to the semi-analytical and localization nature of the IFSM. Benchmark numerical investigations are presented, including the study of a simply supported thin flat shell and a model of the Kap Shui Mun Bridge, an existing long-span cable-stayed bridge. The numerical results show that IFSM significantly improves the convergence of the critical flutter frequencies, and therefore leads to smaller storage requirements and faster flutter eigenvalue extraction. [ABSTRACT FROM AUTHOR]

Abstract For the purpose of meeting the wind field in urban area, the performances of a newly invented cross-axis wind turbine (CAWT), which consists of the advantages of horizontal and vertical axis wind turbines (HAWTs and VAWTs), was examined in a calibrated open-circuit low speed wind tunnel. Firstly, to ensure the quality of the wind tunnel, the evaluations in accordance with the flow uniformity, turbulent intensity and pressure gradient along the test section were conducted within the wind tunnel, based on the IEC61400-12 standard. Furthermore, the CAWT was tested with and without the artificial turbulence generator for examining the static and dynamic performances within the steady/unsteady wind conditions at various Reynolds numbers, and the blockage inside the wind tunnel was additionally taken into account. The results showed that both the static and dynamic performances were improved with the addition of turbulence generator. Moreover, the payback period of the CAWT was calculated associated with its power performance. Highlights • The wind tunnel was examined to ensure the quality of experimental results. • The static and dynamic performances of CAWT were tested with unsteady flow. • The performance of CAWT under unsteady condition is better compared to steady one. • The payback period of CAWT was calculated based on the power performance. [ABSTRACT FROM AUTHOR]

Highlights • Parameterizations of street trees in CFD microscale modelling are reviewed. • The contribution of aerodynamic, deposition, resuspension and thermal effects on air quality is assessed. • Parametrizations of resuspension and thermal effects is still poorly evaluated. • Systematic and comprehensive experiments of the whole role of street trees are still missing. Abstract This paper reviews current parameterizations developed and implemented within Computational Fluid Dynamics models for the study of the effects linking vegetation, mainly trees, to urban air quality and thermal conditions. In the literature, passive mitigation via deposition is parametrized as a volumetric sink term in the transport equation of pollutants, while a volumetric source term is used for particle resuspension. The aerodynamics effects are modelled via source and sink terms of momentum, turbulent kinetic energy and turbulent dissipation rate. A volumetric cooling power is finally considered to account for the thermal (transpirational cooling) effects of vegetation. The most recent applications are also summarized with a focus on the relative importance of both aerodynamic and deposition effects, together with recent studies evaluating thermal effects. Those studies have shown that the aerodynamic effects of trees are stronger than the positive effects of deposition, however locally the pollutant concentration increases or decreases depending on the complex inter-relation between local factors such as vegetation type and density, meteorological conditions, street geometry, pollutant characteristics and emission rates. Unlike aerodynamic and deposition effects on pollutant dispersion which were also found in street far from trees, the thermal effects were in general locally restricted to the close vicinity of the vegetation and to the street canyon itself. Future requirements in CFD modelling include more in depth investigation of resuspension and thermal effects, as well as of the VOCs emissions and chemical reactions. The overall objective of this review is to provide the scientific community with a comprehensive summary on the current parameterizations of urban vegetation in CFD modelling and constitutes the starting point for the development of new parametrizations in CFD as well as in mesoscale models. [ABSTRACT FROM AUTHOR]

The single layer Penman-Monteith (PM) method is widely used method for the estimation of crop evapotranspiration (ET c ). The accuracy of ET c estimate relies upon the quality of input weather data and capacity to approach adequately canopy (r c ) and aerodynamic resistance (ra). In this study, the PM method was used to estimate daily crop evapotranspiration of irrigated maize for the years 2013 and 2014 in a sub-humid region. Four different approaches ( Monteith, Katerji-Perrier, Todorovic , and Jarvis ) were used to estimate canopy resistance and, then after, crop evapotranspiration by PM equation were evaluated. The comparison was made to daily crop evapotranspiration obtained from the soil water balance (SWB) and soil water content variation measured by time domain reflectometry (TDR) . The cumulative crop evapotranspiration of SWB , Monteith, Katerji-Perrier, Todorovic and Jarvis approach was respectively, 260.4, 266.8, 252.8, 263.4, 256 mm for the year 2013, and 250.5, 257.7, 240.6, 251.8, 247.6 mm for the year 2014. The comparison of results and the statistical analysis confirmed that Todorovic and Jarvis approach gave reliable values, while the Katerji-Perrier approach could be used as an alternative method. [ABSTRACT FROM AUTHOR]

This paper reviews current parameterizations developed and implemented within Computational Fluid Dynamics models for the study of the effects linking vegetation, mainly trees, to urban air quality and thermal conditions. In the literature, passive mitigation via deposition is parametrized as a volumetric sink term in the transport equation of pollutants, while a volumetric source term is used for particle resuspension. The aerodynamics effects are modelled via source and sink terms of momentum, turbulent kinetic energy and turbulent dissipation rate. A volumetric cooling power is finally considered to account for the thermal (transpirational cooling) effects of vegetation. The most recent applications are also summarized with a focus on the relative importance of both aerodynamic and deposition effects, together with recent studies evaluating thermal effects. Those studies have shown that the aerodynamic effects of trees are stronger than the positive effects of deposition, however locally the pollutant concentration increases or decreases depending on the complex inter-relation between local factors such as vegetation type and density, meteorological conditions, street geometry, pollutant characteristics and emission rates. Unlike aerodynamic and deposition effects on pollutant dispersion which were also found in street far from trees, the thermal effects were in general locally restricted to the close vicinity of the vegetation and to the street canyon itself. Future requirements in CFD modelling include more in depth investigation of resuspension and thermal effects, as well as of the VOCs emissions and chemical reactions. The overall objective of this review is to provide the scientific community with a comprehensive summary on the current parameterizations of urban vegetation in CFD modelling and constitutes the starting point for the development of new parametrizations in CFD as well as in mesoscale models. [ABSTRACT FROM AUTHOR]

The planing trimaran has unique rapidity and stability. In this paper, wings are added to the planing trimaran to provide additional aerodynamic lift in high-speed range (volume based Froude number ranging from 4.37 to 8.74), achieving the purpose of reducing the resistance of the planing trimaran. By solving Reynold-Averaged Navier-Stokes(RANS) equations and combining SST k-omega turbulence model with Volume of Fraction(VOF) method, a numerical simulation method is established to analyze the motion characteristics of the planing trimaran. The geometry and airfoil profiles are mainly studied in this paper. The geometry of wings includes rectangular wings, trapezoidal wings, and swept wings. The profile shape of the wing includes three series of NACA wings and two special wings. And the impact of different wings on the planing trimaran rapidity by comparing its hydrodynamic characteristics and aerodynamic characteristics are analyzed. The comparison shows that adding wings to the planing trimaran can significantly reduce the resistance at high speed, with trapezoidal wings having the best aerodynamic performance. All airfoils mentioned in the article can reduce resistance by about 20% at the highest speed, and the airfoil named 1# can reduce the resistance by up to 33.2%. • The wings are added to the planing crafts to produce aerodynamic lift which can change the motion attitude of the planing crafts. • When the volume Froude number is greater than 4.37, the planing trimaran with wings can significantly reduce resistance. • Among rectangular wings, swept wings, and trapezoidal wings, trapezoidal wings have the best effect on improving the speed of the planing craft. [ABSTRACT FROM AUTHOR]

Many previous studies have focused on characterising Reynolds number effects and skinsuit design to better understand and improve aerodynamic performance. However, the majority of this research has been conducted in wind tunnels with turbulence intensities of less than 2%, considerably lower than that experienced when competing outdoors or in the wakes of competitors. In this systematic experimental study using passive turbulence generation, the influence of freestream turbulence on the aerodynamics of a cyclist is determined. Force measurements, wake velocity surveys, total pressure measurements and surface flow visualisations are used to characterise and quantify the aerodynamic behaviour. It is found that the aerodynamic drag is strongly affected by turbulence with it monotonically decreasing with increasing turbulence level. Moderate levels of turbulence are shown to alter local flow separation, and consequently the drag, on parts of the cyclist's body, which in turn is imprinted on the large-scale wake structures. The interaction of turbulence level and skinsuit roughness on the arms is also considered showing that these factors cannot be treated in isolation. Overall, this study highlights the importance of understanding the environment in which cyclists compete in order to optimise their performance. • The aerodynamic drag of a cyclist is highly sensitive to turbulence. • Turbulence alters local separation points of the geometry. • The development of the large-scale structures is affected by turbulence. • A smooth cyclist has lower aerodynamic drag than a skin suit in high turbulence. • Turbulence and Reynolds number have a similar effect on aerodynamic drag. [ABSTRACT FROM AUTHOR]

The planing trimaran has unique rapidity and stability. In this paper, airfoils are added to the planing trimaran to provide additional aerodynamic and hydrodynamic lift, achieving the purpose of reducing the resistance of the planing trimaran. By solving Reynold-Averaged Navier-Stokes (RANS) equations and combining SST k-Omega turbulence model with Volume of Fraction (VOF) method, a numerical simulation method is established to analyze the motion characteristics of the planing trimaran. The attack angle and the height of airfoils are mainly studied in this paper. NACA4404 and a special airfoil named 2# airfoil are selected as the research objects. The range of attack angle is 0–8°. The drag reduction effect of the airfoil does not change linearly with the increase of the attack angle in the high speed range. NACA4404 and 2# airfoil have the best drag reduction effect at 2°and 4°respectively. The range of airfoil height is 0.8h–1h ("h" is the wing height from baseline). For NACA4404, lower wing height is beneficial to reduce the resistance, especially in the low speed range. The 2# airfoil has poor performance in the low speed range after reducing the height, and can increase the resistance by up to 16.3%. • Adding the airfoils to the planing trimaran has great effect on reducing total resistance. • Properly changing the attack angle and the height of the wing can help reduce the resistance of the planing craft. • As the attack angle of the wing increases, there is an optimal attack angle that maximizes the drag reduction effect. [ABSTRACT FROM AUTHOR]

In this paper, results of WindPACT 1.5 MW baseline horizontal axes wind turbine aeroacoustic and aerodynamic optimization are presented. For this purpose, the blade twist, the chord distribution, the airfoils for all sections, and the rotational speed are optimized with Multi-Objective Particle Swarm Optimization (MOPSO) algorithm. The geometric class/shape function transformation technique and Bézier curve are used for geometry parameterization. Improved blade element momentum theory and Brooks, Pope and Marcolini semi-empirical methods are implemented for wind turbine power and aeroacoustic noise calculation in the optimization procedure. MOPSO parametric study is conducted to increase both robustness and speed of the optimization cycle. Optimization objective functions are power output and overall average sound pressure level. After optimization, improved delayed detached eddy simulation is employed to verify the new wind turbine output power and noise sources. The noise propagation to the far field is calculated with the Ffowcs Williams and Hawkings acoustic analogy. Results show about 1 dB noise reduction as well as 6% power increment for the optimized WindPACT wind turbine. [ABSTRACT FROM AUTHOR]

In this paper, the results of aerodynamic and aeroacoustic calculation of a MW-class horizontal axes wind turbine (HAWT) are presented. Improved Delayed Detached Eddy Simulation (IDDES), as a hybrid LES-RANS turbulence model, is applied to simulate instantaneous flow field around the HAWT. The noise attenuation in the far field is estimated with the Ffowcs Williams and Hawking's acoustic analogy. Improved Blade Element Momentum (IBEM) theory and Brooks, Pope and Marcolini (BPM) semi-empirical methods also are implemented for wind turbine output power and aeroacoustic noise calculation. The semi-empirical and CFD methods are validated against experimental data of AOC 50/15 HAWT. The results show good agreement with experimental data for both IBEM-BPM and CFD techniques. The contribution of the thickness, loading, and quadrupole sources in far field noise propagation are investigated. Then, those methods are implemented for aerodynamic and aeroacoustic prediction of the NREL's 1.5 MW WP_Baseline HAWT. The Results obtained by CFD and IBEM-BPM techniques are compatible with each other for the 1.5 MW HAWT. [ABSTRACT FROM AUTHOR]

The dispersion of powders in gas flows is relevant in some powder processing techniques, in dry powder inhalers and in particle size analysers, among others. When using small particle sizes, the powder tends to form stronger aggregates and the dispersion becomes more difficult. There are many approaches to the dispersion process but most include collisions as one of the possible agglomerate break-up mechanisms. This is not always a satisfactory solution as particles may get contaminated or reduced. In the present work we explore the dispersion of powder aggregates in an accelerating flow with no particle-wall collisions. We built a fluid-dynamic device with a simple geometry consisting of a sharp slit, producing a rapidly converging flow at the entrance and a planar jet at the exit. A powder feeder exited with an ultrasonic actuator was used to generate single powder aggregates. The stationary flow field was calculated numerically and the velocity and degree of aggregate dispersion were assessed based on imaging results. In all the cases tested, erosion of the aggregates could be observed. In the case with the highest suction pressure, a different mechanism arises, which leads to the disintegration of the aggregate and a significantly better dispersion of the powder. [ABSTRACT FROM AUTHOR]

The purpose of this study is to develop a numerical methodology based on real data from wind tunnel experiments to investigate the effect of the ski jumper’s posture and speed on aerodynamic forces in a wide range of angles of attack. To improve our knowledge of the aerodynamic behavior of the ski jumper and his equipment during the early flight phase of the ski jump, we applied CFD methodology to evaluate the influence of angle of attack ( α = 14°, 21.5°, 29°, 36.5° and 44°) and speed (u = 23, 26 and 29 m/s) on aerodynamic forces in the situation of stable attitude of the ski jumper’s body and skis. The standard k - ω turbulence model was used to investigate both the influence of the ski jumper’s posture and speed on aerodynamic performance during the early flight phase. Numerical results show that the ski jumper’s speed has very little impact on the lift and drag coefficients. Conversely, the lift and drag forces acting on the ski jumper’s body during the early flight phase of the jump are strongly influenced by the variations of the angle of attack. The present results suggest that the greater the ski jumper’s angle of inclination, with respect to the relative flow, the greater the pressure difference between the lower and upper parts of the skier. Further studies will focus on the dependency of the parameters with both the angle of attack α and the body-ski angle β as control variables. It will be possible to test and optimize different ski jumping styles in different ski jumping hills and investigate different environmental conditions such as temperature, altitude or crosswinds. [ABSTRACT FROM AUTHOR]

With the intensification of the greenhouse effect, carbon neutrality has become a global goal. The development of vehicle platoons provides a new idea for energy saving and emission reduction. To explore the practical application prospect of vehicle platoon energy-saving methods and reveal the limitations and improvement direction of current vehicle platoon research, this paper reviews the current research status of vehicle platoon energy-saving methods and analyzes the energy-saving method. The energy-saving methods are summarized from aerodynamic and vehicle speed optimization perspectives. Energy-saving methods based on aerodynamics include field tests, wind-tunnel tests, and CFD. Energy-saving methods based on vehicle speed optimization mainly focus on the acceleration and deceleration behavior optimization of vehicles in the platoon. The limitations and prospects of automotive and vehicle platoon development are also put forward. • Energy-saving methods of platoons based on aerodynamic are reviewed. • Energy-saving methods of platoons based on control and optimization are analyzed. • The prospects of the development of platoons at the national level are discussed. [ABSTRACT FROM AUTHOR]

A new installation at the Anti-Icing Materials International Laboratory was developed to study the effects of icing on the degradation of a hovering drone rotor aerodynamic performance and to test different potential ice protection solutions. Following a study on icing parameters effects on aerodynamic performance, this paper studies a methodology developed to assess the performances of coatings as a potential ice protection system under severe icing conditions and rotor speeds up to 4950 RPM. Four different coatings, commercial or under development, were applied to the rotor blades and their effect on the resulting ice accumulation and aerodynamic degradation were measured and compared to those previously obtained on similar, uncoated blades. Results show that passive icephobic coatings in general are a promising solution to limit the negative effect of icing conditions for drone applications, without any additional energy consumption from the system. Moreover, the repeatability assessment of tests under similar conditions and for the same coating showed agreement within ±5% between repetitions, showing no signs of ice protection efficiency degradation for any of the tested coatings. • The work of this article marks the continuity of a series of studies done with a new spinning rotor drone test setup in hover flight mode performed at the 9-m high cold chamber of the Anti-Icing Materials International Laboratory (AMIL). Four different surface protection coatings are applied on their own set of blades for testing in the cold room. The resulting ice accumulation and performance degradation of the spinning rotor are then monitored, recorded and compared to the results obtained of bare uncoated blades. The effects and performances of the coatings tested are then assessed. • This report presents a new test methodology and setup to assess the performances of protective surfaces as a passive ice protection system for small and medium drone rotors, which differs than for the rotorcraft application actually found in the literature. It also presented unique results on the possibility of using those surfaces for drones, which cannot be simply deduced from rotorcraft studies found in the literature. This demonstrates the importance of this work and of this new methodology and test setup for the industry since the literature greatly lacks reported data of similar icing tests using ice protection coatings on a UAV. • This first test campaign has proven the ability of icephobic surface coatings to efficiently perform as ice protection systems. Moreover, coatings have a positive potential of being combined with an active ice protection system (such as electrothermal) as a way to reduce the power consumption of those systems. Further research will be done with additional products and also combined with active ice protection systems to help lower their power consumption. [ABSTRACT FROM AUTHOR]

The planing trimaran possesses distinctive hybrid hydrodynamic and aerodynamic performance due to the presence of tunnel. The research described in this paper was carried out based on the observation of wave characteristics of a planing trimaran model in towing tests, in which the resistance drops as soon as the wave surface separates from tunnel roof. In order to gain a deeper insight into the relationship between wave flow and forces in tunnel region, a comprehensive series of viscous CFD simulations considering free-surface and 2-DOF motion of the hull (heave and pitch) have been performed for the tested model at the volume based Froude numbers ranging from 3.16 to 5.87. The calculated results were validated by comparison with experimental data and showed good agreement. Numerical results of wave contours, longitudinal wave cuts and lifting force distributions at the calculated speeds were presented for the analysis of ventilation process in tunnel region and the corresponding variation of tunnel forces. It is found that, for the speeds higher than Froude number of 4.52, the aerodynamic forces provide major tunnel lift and mainly act on the straight section of the tunnel. And, therefore, numerical simulations of two modified models have also been performed for the analysis of influence of straight section length on the hydrodynamic and aerodynamic performance of planing trimaran. [ABSTRACT FROM AUTHOR]

Unsteady numerical studies were conducted on the effects of combustor exit total pressure non-uniformity and hot streak (HS) on the aero-thermal characteristics of a high-pressure (HP) turbine stage. Firstly, four total pressure profiles including uniform, turbulent boundary layer, realistic engine combustor exit and radial reverse total pressure (higher total pressure near the endwall) were applied to reveal the vortex structures and heat transfer characteristics of the turbine. Then the four total pressure profiles coupled with inlet HS were specified to study the HS migration mechanisms. The results indicated that the turbulent boundary layer total pressure intensifies the passage vortices (PVs) while the higher total pressure near the endwall induces counter rotating vortices (CRVs), in both the stator and rotor passages. The heat transfer on the vane and blade surfaces was affected by the vortices and the extent of the impact directly depends on the intensity of the vortices, which is determined by the gradient of the total pressure. The heat transfer coefficients (HTCs) on the vane and blade pressure surface are increased by 104% and 20–30%, respectively, due to the CRV effects. The increase of tip leakage flow for the higher total pressure near the tip enhances the tip pressure side HTC by 4% comparing with the uniform case. The PVs and CRVs from the stator passage persistently exist in the rotor passage near the suction side endwall while have negligible influence on the rotor heat transfer. The migration paths of the hot streak are significantly affected by the PVs and CRVs in the stator passage, and the rotor blade surface temperature is dominated by both of the redistribution of HS in the vane passage and the vortices in the rotor passage. The PVs extend the HS radial migration and increase the vane and blade surface temperature. While the CRVs circulate the hot fluid away from the vane surface and increase the HS attenuation, thus decrease the vane and blade surface temperature significantly. The total pressure non-uniformity also decreases the turbine adiabatic efficiency by 0.6% at uniform inlet temperature condition. [ABSTRACT FROM AUTHOR]

This work describes a model developed to analyze the aerodynamic loads on a helicopter model on conventional configuration implemented with VehicleSim, a multibody software specialized in modelling mechanical systems composed by rigid bodies. The rotors are articulated and the main rotor implementation takes into account flap, lag and feather degrees of freedom for each of the equispaced blades as well as their dynamic couplings. This article presents an aerodynamic model that allows to simulate hover, climb, descent and forward flight as well as trajectories under the action of several aerodynamics loads. The aerodynamic model has been built up using blade element theory. All the dynamics, aerodynamic forces and control action are embedded in a single code, being this an advantage as the compilation time is greatly reduced. The software used in this work, VehicleSim does not need external connection to other software. This new tool may be used to develop robust control methods. The nonlinear equations of the system which can be very complex, are obtained, in particular, this article presents the equations for flap and lag degrees of freedom in hover flight. The control approach used in here consists of PID controllers (proportional, integral, derivative), which allow to use VehicleSim command exclusively to simulate several helicopter flight conditions. The results obtained are shown to agree with the expected behaviour. [ABSTRACT FROM AUTHOR]

The implementation of the Kyoto Protocol in 2005 and similar international agreements has placed greater demands related to the control of carbon dioxide emissions on the governments of signatory countries. This article shows a detailed comparison of the same modern industrial low-pressure turbine. This low-pressure turbine, LPT (low pressure turbine), is part of a modern gas turbine used currently for electricity production. The comparison is focused on the LPT's phenomenology working with the fluid present in normal conditions and with the new fluid present in semi-closed cycles with oxy-combustion for CO2 capture. The study used CFD (computational fluid dynamic) methods for this purpose, among them 3D multirow CFDs. [ABSTRACT FROM AUTHOR]

Summary Objectives The two goals of the present study were to (1) determine the ability of commonly used aerodynamic voice measures to capture change as a function of known interventions and (2) determine if certain aerodynamic measures demonstrate better responsiveness to change in specific disorder types than others. Study Design This is a retrospective, longitudinal, single-blinded, cross-sectional study. Methods Patients (n = 70) with a single voice disorder diagnosis of benign vocal fold lesions (lesions), unilateral vocal fold paralysis (UVFP), primary muscle tension dysphonia (MTD-1), or vocal fold atrophy (atrophy) underwent baseline testing, a single intervention (phonosurgery or voice therapy), and follow-up testing. Common aerodynamic measurements were completed in repeated syllables and an all-voiced sentence. Results Statistically significant improvements were observed for two outcome measures, average airflow in syllables, and average airflow in the all-voiced sentence. Patients with lesions, UVFP, and MTD-1 improved in average airflow in the all-voiced sentence. Patients with UVFP also improved in airflow in syllables. Conclusions Average airflow in the all-voiced sentence changed as a function of treatment for the lesion, MTD-1, and UVFP groups, demonstrating a disorder-specific pattern. Laryngeal airway resistance, and estimates of average subglottal pressure did not show significant change. Average airflow in the all-voiced sentence measurements is recommended as a routine voice measure, and further investigation of other aerodynamic measures' sensitivity to change is warranted. [ABSTRACT FROM AUTHOR]

Although airborne urban particles are a concern for air quality and human health, little information exists on the levels and characteristics of microplastics (MPs) and microrubbers (MRs) in this setting. In the present study, MPs and MRs are quantified and characterised in road dusts and accumulations captured passively (and up to elevations of 177 cm above road level) in the steps of utility poles at 18 locations throughout the city of Shiraz, southwest Iran. Dust accumulation rates were greatest at road level (median = 45 g m−2 month−1) and declined with elevation (median = 2.0 g m−2 month−1 at 177 cm). The accumulation rates and concentrations (per g of dust) of MPs and MRs were more variable between locations but accumulation declined with elevation for both particle types and MR concentration (up to ∼27,000 MR g−1) was always greater than corresponding MP concentration (up to ∼3300 MP g−1). Increasing elevation was also accompanied by an increasing proportion of fine (≤100 μm) and fibrous particles, and in particular for MPs. Fractionation in the quantities and characteristics with elevation above road level are attributed to the extent of resuspension of MPs and MRs from the road surface by wind and passing traffic, with aerodynamic considerations predicting the greatest and most widespread resuspension of fibrous MPs. The fractionation of MPs and MRs with elevation above road level also results in different exposures for adults and children. [Display omitted] • Microplastics (MPs) and microrubbers (MRs) measured in Shiraz urban dusts. • MP/MR concentrations spatially variable but declined with height (<2 m) from road level. • Proportion of finer and fibrous particles increased with elevation. • Observations attributed to resuspension from road surface by wind and traffic. • Different MP/MR exposures are predicted for adults and children. [ABSTRACT FROM AUTHOR]

A high-speed train that accelerates under crosswinds can potentially encounter dramatic aerodynamic effects and safety risks. The goal of this study is to reveal the effect of wind speed on the instantaneous vortex structures, pressure distribution, aerodynamic loads and safety indicators of a high-speed train that is accelerating under crosswinds. The three-dimensional and incompressible IDDES method combined with moving overset grid technology is applied to obtain reliable results. The main results are summarized as follows: two typical inclined vortices on the leeward side are observed, and the amplitude and area of the negative pressure in the vortex core region increase with increasing wind speed. The leeward side and the roof exhibit severe pressure fluctuations, and the sensitivity of the pressure from wind speed on the head car is stronger than that on other carriages. For aerodynamic force/moment coefficients, local maximum/minimum values appear during the acceleration process; a reasonable inference for this phenomenon is that a certain range of yaw angles causes the force/moment coefficient to reach the local maximum/minimum values. Wind speed has a significant increasing effect on the maximum values of the lateral force coefficient and rolling moment coefficient, especially for the head car. Although the overturning coefficient and derailment coefficient are less than the prescribed safety thresholds, the overturning risk needs more attention than the derailment risk considering that the maximum value of the overturning coefficient is twice that of the derailment coefficient. The obtained numerical results can provide a preliminary reference for train accelerations under crosswind. • The temporal and spatial pressure distributions on a train were investigated. • The local maxima/minima of the aerodynamic coefficients were observed during acceleration. • The operational safety for different wind speeds was assessed based on the train multi-body dynamics simulation method. [ABSTRACT FROM AUTHOR]

Noise pollution from wind turbines is an important public health issue, and strict regulations regarding noise levels for nearby residents to a wind farm is a necessity. The fact that more turbines equals higher noise levels constitutes a problem, an expansion of turbines is needed but the nearby residents should not be affected. Noise levels can be measured, but, similar to other environmental attentions, the public's perception of the noise impact of wind turbines is in part a subjective determination. Vertical axis wind turbines are suitable to be established within the densely populated city area. Therefore, the noise item is very important parameter to investigate. In this work, it is introduced an innovative design of the lift VAWTs (vertical axis wind turbines) to reduce the noise emissions. Every blade in the turbine is constructed by two airfoils. The aerodynamics field of the new design have been investigated numerically to obtain the generated noise from new blades. Unsteady Reynolds-averaged Navier–Stokes (URANS) equations are used to obtain the time-accurate solutions. The spacing between the airfoils in every blade at different tip speed ratio has been studied in this work. The results indicated that the 60% spacing is the best configuration of the double-airfoil from the noise reduction point of view. This new design reduces the generated noise by 56.55% [ABSTRACT FROM AUTHOR]

The planing trimaran hull has unique hydrodynamic performance due to the tunnel region. In this paper, results of experimental and numerical studies for the planing trimaran hull are presented to analyze the hydrodynamic characteristics of tunnel and its effect on the hull body. Model tests were carried out for volume based Froude number ranging from 0.90 to 5.87. Resistance, sinkage and trim angle obtained by towing tank show that the planing trimaran has poor resistance performance at the hump region, while it operates quite well in the planing mode. A three dimensional computational fluid dynamic (CFD) code based on the Finite Volume Method (FVM) was used to simulate the forward motion of the hull body with two degrees of freedom (heave and pitch) when Froude number is above 3.16. Calculated results were validated with the experimental data and showed good agreement. Wave profile, dynamic lift, longitudinal center of pressure and flow vectors in the tunnel region at various Froude numbers were provided to explain the hydrodynamic and aerodynamic mechanism of this region. At last, models with different tunnel height and beam were calculated to study the influence of tunnel configuration on hull behaviors and hydrodynamic performance. [ABSTRACT FROM AUTHOR]

A multichannel cyclone is new generation air treatment equipment that can remove fine stiff particles of up to 2 °m from air flow and reach the general effectiveness of 95%. The carried out research is aimed at establishing parameters for the dynamics of the gas-vapour two-phase flow in the cyclone and treatment efficiency removing stiff lignin particulate matter, i.e. under the increased humidity and temperature of the purified flow. The article describes the peculiarities of parameters for the cyclone-separator and analyses the results of the cyclones having different inner structures under conditions of an aggressive environment. The flow polluted with lignin particulate matter has been treated under simulation conditions in the laboratory, at the gas flow temperature of 28-30 °C and gas flow humidity of 85-95%. Under an average vapour-PM flow velocity of 12 m/s in the cyclone polluted with ultra-dispersive 20 μm lignin particulate matter and conditions of the aggressive environment, treatment efficiency equals 82.5%. [ABSTRACT FROM AUTHOR]

Objective. This study aimed to evaluate vocal changes in pregnancy according to trimesters both objectively and subjectively. Methods. Fifty pregnant women and 15 nonpregnant women were included in the study. Eighteen of the 50 pregnant women were in the first trimester, 17 in the second trimester, and 15 in the third trimester of their pregnancies. The fundamental frequency (F0), jitter, shimmer, noise-to-harmonics ratio (NHR), and minimum and maximum pitch were determined during acoustic voice analysis. Laryngologic examination was evaluated via reflux finding score (RFS). Voice Handicap Index 10 (VHI-10) was used for subjective analysis. Results. Maximum phonation time (MPT), VHI-10, and RFS were the parameters that differed significantly.MPTwas significantly shorter in the third trimester. Acoustic analysis revealed that F0, jitter, shimmer, NHR, and minimum and maximum pitch values were not significantly different in any groups. RFS was higher in the first and third trimesters than the second trimester and control groups. VHI-10 scores were significantly higher in the third trimester. Conclusions. Our results showed that MPT is decreased during the third trimester, although acoustic parameters did not differ. VHI-10 results deteriorated in the third trimester significantly. [ABSTRACT FROM AUTHOR]

Centrifugal compressors are used in many heat pumps and refrigeration systems. Radial vaneless diffuser is a principal component in these compressors. Therefore, the present research aims at improving the centrifugal compressor performance by optimizing the design of the radial vaneless diffuser. Two radial vaneless diffuser geometries were proposed, investigated and numerically optimized. The optimization aimed at minimizing the diffuser loss coefficient and maximizing the pressure coefficient. Simulations were performed by solving the Reynolds averaged Navier–Stokes equation under 2D axisymmetric condition. A genetic optimization algorithm was implemented in order to conclude the optimum diffuser geometry. 2D axisymmetric simulations with air and R134a as working fluids showed that the optimized geometry reduced the diffuser loss coefficient by up to 10% and increased the pressure coefficient by up to 3.8%. Additional 3D simulations with an impeller located before the diffuser were performed. These 3D simulations showed that the optimized diffuser geometry reduced the diffuser loss coefficient by up to 4.7% and increased the pressure coefficient by up to 6.6% under jet-wake and swirl flow conditions. [ABSTRACT FROM AUTHOR]

Summary Objectives This pilot study examined voice outcomes and patient perceptions after intensive voice therapy for vocal fold nodules via telepractice. Study Design. Pilot, within-subjects experimental trial. Methods Participants included 10 women diagnosed with bilateral vocal fold nodules who received intensive voice treatment via a free videoconferencing platform Skype , (Microsoft Corp., Redmond, WA). All participants completed one vocal hygiene session in person, followed by eight sessions of therapy via telepractice over 3 weeks. Before and immediately after treatment, patients attended a clinic in person to complete perceptual, stroboscopic, acoustic, and physiological assessments of vocal function. Analyses were performed by a speech-language pathologist and an otolaryngologist independent to and blinded to the study. Participants also completed the Voice Handicap Index and a telepractice satisfaction questionnaire, or an anticipated satisfaction questionnaire, before and after the treatment. Results Significant improvements were found in perceptual, vocal fold function, acoustic, and physiological parameters as well as nodule sizes and patient perceptions of voice-related quality of life post-treatment. Participants were highly positive about their first experience with telepractice. Results were similar to those from a separate study investigating the effects of an intensive voice therapy delivered in conventional face-to-face (FTF) format. Conclusions This study is consistent with possible benefits of telepractice in the delivery of intensive treatment for vocal fold nodules. Pending final verification with a FTF comparison group, telepractice could be recommended as an alternate treatment modality for patients with vocal fold nodules. [ABSTRACT FROM AUTHOR]

This paper examines the aerodynamic behaviour of a standard 2-man bobsleigh including the crews. The body position of the brakeman was studied over a range of angles from 25 to 90 degrees relative to the wind direction. Wind tunnel experiments were undertaken on a 50% scale model of 2-man bobsleigh and the crews. Aerodynamic drag forces were measured over a range of wind speeds (40 to 120 km/h) in the wind tunnel environment. Additionally, wool tufts and smoke were used to visualise the airflow characteristics around the bobsleigh and crews. The results show that the body inclination angle of the brakeman has significant effect on the overall aerodynamics of bobsleighing and the most aerodynamic body position of the brakeman was found at 55 degree with the minimal drag. The results also indicate that this particular body position of the brakeman can reduce the drag over 10% compared to his body position at 90 degree. However, the brakeman's body position over 35 degree indicates an increase of drag. [ABSTRACT FROM AUTHOR]

Summary Objectives The aim of this paper is to compare the aerodynamic parameters of intraoral pressure (IOP), oral airflow (OAF), and estimated transglottal pressure of 10 French patients treated by a cordectomy of types II-III with a group of 10 French healthy subjects. Study Design Prospective. Methods The collection of the aerodynamic data was conducted with EVA2. Parameters were measured using logatomes of the type CV 1 ·CV 2 ·CVC 3 where C represents [p,b] and V is one of the vowels [a,i,u] in the positions one and two (n = 240). The maximum peaks of IOP of the plosives [p] and [b] and the maximum peaks of OAF at their releases were extracted. Finally, the transglottal pressure was estimated, necessary for the voicing of [b], to establish the difference in the IOP mean peak of [p] and [b] at the same intensity. Subsequently, the differences in IOP for both positions and each vocalic contexts, “IOP(p-b)” were calculated, and the reports of these differences for the IOP of [p], viz “IOP(p-b)/IOP(p)”, were established for a normalization of the results. Results This study highlights an increase of the IOP and the OAF in voiceless contexts for both groups. The elevation of both parameters observed for the patients—confirmed by the calculation of the estimated transglottal pressure—does show some degree of laryngeal incompetence. Conclusions The patients treated by cordectomy of types II-III maintain a relatively good voicing contrast. A certain difficulty in the execution of this articulatory feature is found. [ABSTRACT FROM AUTHOR]

Summary Objective The purpose of this study was to describe changes in aerodynamic and electroglottographic (EGG) measures immediately after completing three semi-occluded vocal tract (SOVT) exercises. Study Design Prospective case series. Methods Aerodynamic and EGG measurements were obtained before and immediately after performing three SOVTs (straw phonation, lip trill, and tongue trill) in four singers for prepost comparisons to evaluate laryngeal changes persisting beyond the execution of SOVTs. Results Mean air flow, sound pressure level, and EGG closed quotient tended to increase after completing SOVTs. The magnitude of change and consistency of change in measures across the SOVTs varied from subject-to-subject. Conclusions Aerodynamic and EGG changes did occur during and immediately after completing SOVTs. However, there was marked variability within and across participants. Further investigation is needed to better understand which SOVTs are likely to benefit a particular individual. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study on the unsteady pressure loading for two circular cylinders in tandem arrangement for the Reynolds number in the subcritical regime. Experiments were conducted on two heavily instrumented cylinders, each with multiple static and dynamic pressure sensor devices positioned at various peripheral and spanwise locations, enabling extensive dynamic surface pressure, coherence, and turbulence length-scale analysis. Results show that the root-mean-squared pressure magnitude of the pressure distribution results is much larger for the rear cylinder than for the front cylinder. In the case of small spacing ratios, the surface pressure density findings show a decreased shedding frequency on both cylinders, however the critical spacing ratio shows a quick jump in shedding frequency. The lateral coherence results also revealed that beyond the critical spacing, a prominent peak at the fundamental vortex shedding frequency exists, with weaker peaks at shedding harmonics on the front and rear cylinders, resulting in smaller correlation length values than those for smaller spacing ratios. The discovery of tonal peaks and their associated flow mechanics on cylinders in tandem were reinforced by the lift and drag power spectral density as well as the higher-order spectral analysis, such as wavelet analysis and persistence spectrum. • The fluctuating pressure exerted over the circumference of the tandem cylinders. • Surfaces of cylinders are exposed to the growth of the turbulence structure. • The spanwise length scale of the shedding structures and its frequency dependence. • Discovery of tonal peaks and their associated flow mechanics on cylinders in tandem. [ABSTRACT FROM AUTHOR]

Coupled thermo-elastohydrodynamics model has been developed to predict three-dimensional thermal, structural and hydrodynamic performance of foil bearings. Bearing deformation and film pressure has been coupled in FEM considering thermal/centrifugal growths, and thermo-mechanical material properties. Energy equation has been solved for film temperature using FDM, which is also coupled to FEM via successive iterations. Augmented-Lagrangian method and thermal contact models have been applied to solve for mechanical and thermal contacts. The predicted values have been benchmarked against published measurements, which indicated reasonable correlation. A parametric study has been conducted for various shaft speeds and load conditions to visualize bearing performance. [ABSTRACT FROM AUTHOR]