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The Empty Quarter Desert, one of Earth's major dust sources, frequently experiences dust storms due to wind erosion. Despite its significance as a primary dust source on a global scale, in‐situ observations from this region had not been reported until very recently. In summer 2022, the WInd‐blown Sand Experiment (WISE) Phase‐1 was initiated in the Empty Quarter Desert of the United Arab Emirates, and continued until 7 February 2023. Utilizing a diverse array of instruments, we measured winds, temperature, humidity, radiation fluxes, saltation, and the physical and optical properties of dust aerosols, atmospheric electric fields, and soil characteristics. A total of 38 distinct sand‐saltation events were recorded from September 2022 to February 2023, with activity peaking between 13:00 and 14:00 local time. Key findings include the identification of dominant wind patterns, and the measurement of the average aerodynamic roughness length (z0) at 0.8 ± 0.6 mm, and the thermal roughness length (zh) at 0.3 ± 0.5 mm—the first estimation of zh for this area. In‐situ observations revealed that dust particle concentrations near the surface increased 1.7‐fold on days with saltation compared to days without it. Moreover, we determined a wind‐speed threshold for initiating saltation at 7.70 m s−1. This comprehensive data set significantly advances our understanding of atmospheric‐soil interactions and sand movement dynamics, providing invaluable insights for ongoing research into desert environments and the global dust cycle. Plain Language Summary: The Empty Quarter Desert, one of the Earth's major dust sources, frequently experiences dust storms due to wind erosion. Despite its importance as a main dust source on a global scale, no in‐situ observations from this region have been reported until very recently. In the summer of 2022, the WInd‐blown Sand Experiment (WISE) Phase‐1 provided crucial data on the arid environment of the Empty Quarter Desert in the United Arab Emirates. Lasting until February 2023, this experiment focused on quantifying environmental and soil characteristics through an array of measurements, including wind direction and speed, temperature, humidity, radiation fluxes, and dust particle concentrations. The study revealed dominant wind patterns, quantified the aerodynamic and thermal roughness of the desert soil, and recorded 38 distinct sand movement events, noting a peak in activity during early afternoon hours. This research is significant for its detailed analysis of particle concentration changes during these events and its establishment of a specific wind speed threshold for sand movement in this region. These findings are invaluable for researchers studying desert environments, particularly in terms of understanding atmospheric‐soil interactions and the dynamics of sand movement. Key Points: First‐of‐its kind experiment in the Empty Quarter Desert to characterize environmental dynamicsThe first estimation of the thermal roughness length (zh) for this desert and is found to be 0.3 mmThe derived wind‐speed threshold for saltation at the Empty Quarter Desert is 7.70 m s−1 [ABSTRACT FROM AUTHOR]

This study relates the structural deformation and the unsteady aerodynamics involved for lift production in bioinspired nanocomposite flapping wings. The sectional chord deformation effects on theoretically supported aerodynamic lift are addressed. Digital image correlation setup and L-shape mechanism are developed and synchronized for wing deformation and aerodynamic forces measurement respectively. DIC system with estimated resolution of 0.159 mm/pixel and L-shape mechanism with net uncertainty of ± 0.72 % verify the measurement accuracy for low Reynolds number flapping wing experiments and alike miniature aero-structures. The flapping wing shape is investigated at 25%, 50% and 75% wing-span to study the effect of sectional chord deformation on lift components obtained from Theodorsen theory. Circulatory lift is dominant at mid-downstroke while Non-circulatory lift is dominant at the beginning of flapping cycle due to inertial effects. [ABSTRACT FROM AUTHOR]

This publication deals with the estimation of viscosity of liquid metals. It is proposed to discuss the possibility to determine this parameter during aerodynamic levitation experiments performed in ground laboratory. Once in liquid state, metallic sample is submitted to acoustic waves through the levitation gas making it oscillate and deform. A high speed camera records the radial periodic deformation during the relaxation period, meaning when incident waves stop. The evolutions of the sample radius over time are extracted from records and compared with analytical model based on the damped oscillator. The estimation of viscosity is performed by inverse method and leads to overestimated values by comparison with expected values. Then, numerical simulations (CFD) including or not levitation gas and gravity are performed to show the impact of gravity during measurements. New viscosity estimations show that the damped oscillation model (Lamb's theory) as it is classically used is not valid in aerodynamic levitation due to the influence of both gravity and gas. [ABSTRACT FROM AUTHOR]

In this paper, a combined theoretical and experimental study is carried out to investigate the spanwise effect of turbulence on the aerodynamic lift on a wing with different aspect ratios. The ratio of the mean square variance of the aerodynamic lift calculated by the commonly used strip theory and the two-wavenumber buffeting theory is analyzed comprehensively for the wings with different aspect ratios in turbulence with various integral scales. To validate the theoretical analysis and achieve a deeper understanding of the spanwise effects of turbulence, wind tunnel experiments are performed on National Advisory Committee for Aeronautics 0015 airfoils in grid-generated turbulent flows with different integral scales. The results demonstrate that it is essential to use the two-wavenumber buffeting theory to account for the spanwise effect of turbulence when calculating the aerodynamic lifts on wings with small aspect ratios, especially when in small-scale turbulence. The deviations between the equivalent two-wavenumber coherence function and the spanwise effect influence function at low reduced streamwise wavenumbers are the underlying causes for spanwise effects of turbulence. To achieve reliable wind tunnel testing results, appropriate simulations of the ratio of the turbulence integral scale to the chord are very important in the measurements of aerodynamic lifts on finite-span wing sections, especially for those with small aspect ratios. [ABSTRACT FROM AUTHOR]

With the continuous warming of the global climate, expanding the use of renewable energy has become one of the main social responsibilities. However, as the number of installed wind turbines and their physical dimensions continue to increase, the issue of generated noise has become increasingly significant in influencing the acceptance and endorsement of wind power projects by neighboring communities. In this paper, we investigated the noise generated by two wind turbine units with rated powers of 1.5 MW and 4.5 MW and analyzed the variations in low-frequency noise during their operation and shutdown periods. This research shows that the power of a single unit has a significant impact on the low-frequency noise emitted into the environment. Compared with 1.5 MW wind turbines, 4.5 MW wind turbines generate more low-frequency noise when operating at the same wind speed. Further analysis of the narrowband frequency spectra and one-third octave spectra of the measured noise indicates that the low-frequency noise from the 4.5 MW wind turbine increases significantly in the range of approximately 80 Hz to 300 Hz, with more pronounced variations below 250 Hz corresponding to changes in wind speed. However, the overall variations in low-frequency noise with wind speed are not as notable as those observed for the 1.5 MW wind turbine. Due to the relatively weak attenuation of low-frequency noise in the atmosphere, the higher low-frequency content of large wind turbines may cause more distress to residents near wind farms. The result of this study emphasizes that in the planning and design of wind power projects, in addition to considering the efficiency of single-unit power generation and the contribution of renewable energy, it is also necessary to pay full attention to noise emission issues to ensure that the project is widely supported and accepted in the community. [ABSTRACT FROM AUTHOR]

In this study, experimental investigations pertaining to aerodynamic noise are conducted in a hypersonic quiet wind tunnel, which possesses the unique capability of operating in both quiet and conventional modes, achieved by controlling the bleed slot to regulate the boundary layer flow. The measurement of aerodynamic noise and analysis of coherent structures of hypersonic turbulence are accomplished employing pressure probes and the nano-tracer-based planar laser scattering technique. The characterization of aerodynamic noise within the freestream unveils that noise generated by turbulent structures on the nozzle wall is the primary factor affecting the turbulence intensity of the freestream flow. Regarding the acoustic radiation noise generated by the turbulence on the nozzle wall, a peak frequency ranging from 54 to 57 kHz is observed in its spectrum within a unit Reynolds number range of 0.3 × 10 7 – 1.1 × 10 7 m − 1 . Under different operation modes, the freestream pitot-pressure data feature the similar spectral slope of f − 2.2 and f − 12 before and after the aforementioned peak. Through wavelet analysis, scales of the coherent structure in the turbulent boundary layer are examined, revealing that the maximum energy streamwise scale of the coherent structure is approximately 2.47 mm under the unit Reynolds number of 0.7 × 10 7 m − 1 . The product of this scale with the characteristic frequency of 56 kHz obtained from fluctuating pressure measurements is close to the local sound speed of about 140 m/s. [ABSTRACT FROM AUTHOR]

The article describes the most informative, direct and non-invasive radioaerosol method for studying the main protective mechanisms of the respiratory system, the processes of inhaled substances deposition and clearing them from the lungs due to the mucociliary system function (mucociliary clearance). The method involves inhalation of a diagnostic radioisotope-labelled drug and subsequent analysis of the dynamics of distribution and excretion of this drug. Based on the analysis results, the above-mentioned processes of inhaled substances deposition and clearing them from the lungs are judged. The accuracy of assessing these processes depends on the aerodynamic properties of the inhalant, for which albumin dispersion systems were chosen as the most physiological material. In order to optimize the measurement of parameters of the aerodynamic properties of a diagnostic aerosol, a comparative analysis of different measurement methods and different albumin dispersion systems was performed. It has been established that the most informative and economically feasible method for assessing the aerodynamic properties of an inhalant is the scanning electron microscopy method. This method was used to assess the dispersion systems, i.e. albumin macroaggregates produced by foreign manufacturers and albumin microspheres manufactured using domestic technology. It has been shown that domestic albumin microspheres have optimal aerodynamic parameters for studying the processes of inhaled substances deposition and mucociliary clearance of the lungs. However, to definitively assess the potential use of these albumin microspheres, direct assessment of their deposition in the lungs is necessary. [ABSTRACT FROM AUTHOR]

An experimental study on the effect of active flow control using a synthetic jet mechanism on stall delay for the NACA 0020 airfoil is conducted. The experiments are carried out at an open-suction type wind tunnel at Reynolds number 5x104. In the presented experimental study, aerodynamic force measurements of the airfoil with having different orifice geometries (cylindrical, rectangular, sinusoidal, v-type, inclined rectangular) are examined by using a speaker type actuator in synthetic jet mechanism. It is observed that all different orifice geometries are effective in delaying the stall angle of NACA 0020 airfoil. However, it is observed that the inclined rectangular type of synthetic jet geometry is the most advantageous in delaying the stall of the airfoil. The effects of geometric parameters of the actuator on lift and drag coefficient of the NACA0020 airfoil are investigated. Experimental results show that among the all-orifice geometries the rectangular orifice geometry is the most effective in increasing lift coefficient of the airfoil. It is observed that there is a maximum decrease in drag at 10° where the stall occurs. In addition, the decrease in drag is observed after 10° in rectangular, v-type and inclined rectangular orifice geometries. [ABSTRACT FROM AUTHOR]

Objective: This study aimed to classify the degree of edema in patients with Reinke's edema (RE) and examine its impact on their voice parameters using both objective and subjective assessment methods. Methods: Objective and subjective voice data of 104 patients diagnosed with RE between 2018 and 2021 were evaluated retrospectively. RE is classified into 4 groups (types 1, 2, 3, and 4). The evaluation included video laryngostroboscopic examination, acoustic voice analysis, and aerodynamic measurements, GRBAS, Voice Handicap Index-10 (VHI-10), Voice-Related Quality of Life Scale (V-RQOL), and Reflux Septum Index (RSI). Results: Patients with type 1 RE had a significantly lower mean age than those with types 3-4. Although there were no significant differences in acoustic and aerodynamic parameters between the groups, it was observed that F0 and the maximum phonation time decreased as the degree of edema increased. The GRBASTotal, G, and R scores of types 1 and 2 were significantly lower than those of types 3 and 4, as were the scores of type 1 S. There were no statistically significant differences between the RE groups in terms of VHI-10, V-RQOL, and RSI scores. Conclusion: It has been observed that as the severity of RE increases, voice perception and quality (especially types 3 and 4) are negatively affected. Determining the degree of edema will guide the clinician in both the planning of the intervention phase and the follow-up phase. [ABSTRACT FROM AUTHOR]

Highly maneuverable aircraft configurations can be subjected to tail buffeting phenomena at moderate subsonic speeds and medium to high angles of attack. Detailed measurement of the aerodynamic surface pressure fluctuations and the corresponding vibrations is of great importance to investigate these buffeting effects. Fast-response pressure sensitive paint (iPSP) was developed at the German Aerospace Center (DLR) to measure unsteady pressure fluctuation effects in a setup with high-speed cameras. The setup allows a high spatio-temporal resolution of the unsteady surface pressures. In the present paper the iPSP method is applied to a mixed-material, flexible aircraft wind tunnel model with double-delta wing and horizontal tail plane in these flow conditions. The low-speed buffeting effects on the configuration are measured using a synchronized system of five connected high-speed cameras to simultaneously record the unsteady surface pressures with iPSP and the dynamic three-dimensional structural deformation. The present application case is particularly challenging due to low levels of pressure fluctuation in the low-speed regime, multi-frequency aeroelastic phenomena on the model, a long distance between the cameras and the model, as well as the combination of synchronized measurement of unsteady surface pressure and structural deformation. Advanced data analysis methods are applied in a post-processing tool chain to cope with these challenges. The focus of the present paper is the setup of the synchronized measurement chain as well as the data analysis tools. First results are evaluated with respect to iPSP unsteady surface pressures. The root-mean square surface pressures show good agreement with high-fidelity CFD results for the flow conditions of interest. Particular focus of the analysis is on the lessons learned regarding the UV illumination setup, the camera arrangement as well as post-processing tools. [ABSTRACT FROM AUTHOR]

Objective: The aim of this study was to compare the results of voice assessment in stroke survivors with the results of voice assessment in the subacute period and to examine spontaneous voice changes. Material and Methods: The study was carried out with 37 (22 males, 15 females) individuals with a mean age of 66,65±9,63 years. Acoustic and aerodynamic voice assessments [maximum phonation time (MPT) and s/z ratio] were performed. Voice Handicap Index-10 (VHI-10), and Voice-Related Quality of Life (V-RQOL) were applied. All assessments were performed within 1 week and 1 month after the stroke. Results: MPT was 6.279±3.544 in the acute period and 7.461±4.875 in the subacute period. There was no statistically significant difference in aerodynamic measurement results or V-ROQL in the subacute period compared to the acute period (p>0.05). The fundamental frequency value increased statistically significantly in women, men, and all participants. VHI-10 decreased statistically significantly (p<0.05) in all participants. Conclusion: To the best of our knowledge, this is the first study to evaluate the voice of stroke patients in the acute phase using both subjective and objective methods. It was found that the MPT of stroke patients was limited, and the Shimmer values of acoustic parameters were above normal limits. In the subacute phase, it was observed that phonation durations were still low and Shimmer values tended to increase. Therefore, acoustic, aerodynamic, and specific voice evaluations, especially maximum phonation durations, should be performed in stroke patients in the acute period. [ABSTRACT FROM AUTHOR]

A test campaign was conducted in the open-jet test section of the NASA Langley Research Center's 14- by 22-Foot Subsonic Tunnel on a 10%-scale semispan version of the High-Lift Common Research Model incorporating a leading-edge slat, a trailing-edge flap, and removable high-fidelity main landing gear. Computational simulations were used to support the model development, provide important information such as load distributions along the high-lift elements, and aid in the design of noise reduction devices. Aerodynamic and far-field acoustic measurements were obtained on baseline and acoustically treated model configurations using an ensemble of time-averaged and unsteady surface pressure sensors paired with a traversing 97-microphone phased array viewing the pressure side of the airframe. A deconvolution method incorporating corrections for shear layer acoustic wave decorrelation was employed to determine the locations and strengths of relevant noise sources along the span of the slat and in the vicinity of the flap edges and landing gear. The main goal of the test campaign was to use the surface pressure and array data to evaluate the effectiveness of various slat noise reduction concepts. It was found that slat-gap fillers produced significant broadband noise reduction with minimal aerodynamic performance penalties for all Mach numbers and airfoil angles of attack that were investigated. The test campaign clearly demonstrated the noise reduction benefits that can be obtained by applying appropriate treatments to leading-edge slats on commercial transport-class aircraft. [ABSTRACT FROM AUTHOR]

This article proposes a new type of three-component optic fiber balance based on Fabry–Perot displacement measurement technology based on the structure of the pulse wind tunnel balance. This paper systematically introduces the force measurement principle and design process of a three-component optic fiber balance and conducts relevant simulation analysis and experimental verification. The simulation results show that the Fabry–Perot sensor can achieve significant sensitivity to cavity length changes, and when used in existing balance structures, sensitivity gains can be achieved by changing the probe height without the need to modify the original structure of the balance. Finally, the feasibility of the design method was verified through calibration experiments: the optic fiber balance has high sensitivity and good linearity compared to simulation sensitivity, the error is less than 6%, and the calibration accuracy of each component is better than 0.13%, which is better than the existing traditional strain balance (0.37%). The pulse wind tunnel force measurement test has a short test time and a large model mass, and the balance needs to have a large stiffness to meet the short-term force measurement requirements. The introduction of more sensitive optic fiber balance force measurement technology is expected to solve the contradiction between the stiffness and sensitivity of force measurement systems. [ABSTRACT FROM AUTHOR]

The wind tunnel balance signal detection system is widely employed in aerospace applications for the accurate and automated measurement of aerodynamic forces and moments. However, measurement errors arise under different environmental temperature. This paper addresses the issue of measurement accuracy under different temperature conditions by proposing a temperature compensation method based on an improved gray wolf optimization (IGWO) algorithm and optimized extreme learning machine (ELM). The IGWO algorithm is enhanced by improving the initial population position, convergence factor, and iteration weights of the gray wolf optimization algorithm. Subsequently, the IGWO algorithm is employed to determine the optimal network parameters for the ELM. The calibration decoupling experiment and high-low temperature experiment are designed and carried out. On this basis, ELM, GWO-ELM, PSO-ELM, GWO-RBFNN and IGWO-ELM are used for temperature compensation experiments. The experimental results show that IGWO-ELM has a good temperature compensation effect, reducing the measurement error from 20 % F S to within 0.04 % F S . Consequently, the accuracy and stability of the wind tunnel balance signal detection system under different temperature environments are enhanced. [ABSTRACT FROM AUTHOR]

This study investigated the effects of a non-contact boxing exercise program on maximum expiratory pressure and aerodynamic voice measurements. Methods: Eight adult males diagnosed with Parkinson's disease participated in the study. Individuals participated in twice-weekly exercise classes lasting one hour across 12-months. Dependent variables were measured on three baseline days and then at six additional time points. A pressure meter acquired maximum expiratory pressure, and a pneumotachograph system acquired transglottal airflow and subglottal air pressure. Results: Measures of average maximum expiratory pressure significantly increased after 9- and 12- months of exercise when compared to baseline. There was an increasing trend for these measures in all participants, with a corresponding large effect size. Measures of transglottal airflow and subglottal pressure did not change over the course of 9- or 12-months, although their stability may indicate that the exercise program influenced maintenance of respiratory-phonatory coordination during voicing. Conclusions: A non-contact boxing exercise program had a significant effect on maximum expiratory pressure in people with Parkinson's disease. The aerobic nature of the program and challenges to the respiratory muscles potentially explain the "ingredient" causing this effect. The small sample size of this pilot study necessitates future research incorporating larger and more diverse participants. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the concept and efficacy of an adjustable implant (Prototype SH30: porcine implant and APrevent® VOIS: human concept) for treatment of unilateral vocal fold paralysis (UVFP) via in vivo mini‐pig studies, human computed tomographic (CT) and magnetic resonance (MR) image analysis, ex‐vivo aerodynamic and acoustic analysis. Methods: Feasibility testing and prototype implantation were performed using in‐vivo UVFP porcine model (n = 8), followed by a dimensional finding study using CT and MR scans of larynges (n = 75) for modification of the implant prototypes. Acoustic and aerodynamic measurements were recorded on excised canine (n = 7) larynges with simulated UVFP before and after medialization with VOIS‐Implant. Results: The prototype showed in the in‐vivo UVFP porcine model an improved glottic closure from grade 6 incomplete closure to complete closure (n = 5), to grade 2 incomplete closure (n = 2) and grade 3 incomplete closure (n = 1). On human CT/MR scans the identification of the correct size was successful in 97.3% using the thyroid cartilage alar "distance S" as the only parameter, which is an important step towards procedure standardization and implant design. Results were confirmed with implantation in human laryngeal cadavers (n = 44). Measurements of the acoustic and aerodynamic effects after implantation showed a significant decreased phonation threshold pressure (p =.0187), phonation threshold flow (p =.0001) and phonation threshold power (p =.0046) on excised canine larynges with simulated UVFP. Percent jitter and percent shimmer decreased (p =.2976; p =.1771) but not significant. Conclusions: Based on the preclinical results four sizes, differing in medial length, implant width and expansion direction of silicone cushions, seem to be enough to satisfy laryngeal size variations. This concept is significantly effective in medializing UVFP and improving the aerodynamic and acoustic qualities of phonation as reported in a preliminary clinical outcome study with long‐term implantation. Level of Evidence: N/A [ABSTRACT FROM AUTHOR]

The efficiency with which flying animals convert metabolic power to mechanical power dictates an individual's flight behaviour and energy requirements. Despite the significance of this parameter, we lack empirical data on conversion efficiency for most species as in vivo measurements are notoriously difficult to obtain. Furthermore, conversion efficiency is often assumed to be constant across flight speeds, even though the components driving flight power are speed-dependent. We show, through direct measurements of metabolic and aerodynamic power, that conversion efficiency in the migratory bat (Pipistrellus nathusii) increases from 7.0 to 10.4% with flight speed. Our findings suggest that peak conversion efficiency in this species occurs near maximum range speed, where the cost of transport is minimized. A meta-analysis of 16 bird and 8 bat species revealed a positive scaling relationship between estimated conversion efficiency and body mass, with no discernible differences between bats and birds. This has profound consequences for modelling flight behaviour as estimates assuming 23% efficiency underestimate metabolic costs for P. nathusii by almost 50% on average (36–62%). Our findings suggest that conversion efficiency may vary around an ecologically relevant optimum speed and provide a crucial baseline for investigating whether this drives variation in conversion efficiency between species. [ABSTRACT FROM AUTHOR]

Background: Experimental measurement of high-temperature deformation of thermal protection system (TPS) materials and structures of hypersonic vehicles under harsh aerodynamic heating environments is crucial to assess their thermal and mechanical performances. Objective: In this work, a time-gated active imaging digital image correlation (DIC) technique is proposed for measuring full-field high-temperature deformation on the front surface (heating surface) of a test sample subjected to harsh aerodynamic heating. Methods: With the established time-gated active imaging DIC system that mainly composed of a powerful pulsed laser and a gated single-photon camera, the enormous thermal radiation emitted from the heated sample and the quartz lamp heaters can be suppressed to a negligible level by shielding the most transmitted wavelength using a bandpass optical filter and dramatically reducing the exposure time with the gated single-photon camera. Experiments including a comparison test with unblocked/blocked laser and full-field thermal deformation on the front surface of a test sample heated from room temperature up to 1000 °C were performed to verify the viability of the established system. Results: Results indicate that the recorded image by the time-gated active imaging system is rarely affected by the reflected massive thermal radiation from the quartz lamp heaters. By processing the acquired high-contrast images using the regular DIC algorithm, full-field thermal deformation on the sample surface were extracted at each temperature step. Conclusion: It is believed that the time-gated active imaging DIC is a promising technique for characterizing deformation behaviors of TPS materials and structures in extremely high temperatures and/or suffering from strong aerodynamic heating. [ABSTRACT FROM AUTHOR]

The rules governing the dimensions of the Javelin were substantially changed in 1986. It was considered that this new design guaranteed there was zero pitching moment at 0° angle of attack and that the pitching moment decreased (became negative) with increasing angle of attack. The objective of this study is to investigate if the pitching moment remains always negative (nose-down rotation). To measure accurate aerodynamic forces acting on a Javelin, the world's largest 1 m magnetic suspension and balance system was used. The magnetic suspension and balance system was able to measure aerodynamic forces without support interference in the wind tunnel. In addition, computational fluid dynamics were carried out to estimate the pitching moment coefficients. It was found that the pitching moment coefficient of a commercially available Javelin becomes positive (nose-up rotation) at lower angles of attack, less than 12°. The pitching moment becomes positive if the upstream side of the center of gravity receives more inflow than the downstream side. This situation can be attained by, for example, increasing the thickness of the upstream side when compared with that of the downstream side. [ABSTRACT FROM AUTHOR]

FanWing which was investigated in this study has a partially embedded cross flow fan (CFF) and is appropriate for low speed air vehicles that require high maneuverability. The aim of this study is to investigate experimentally and numerically the flow field around FanWing model and the effects of tip speed ratio (TSR) and Reynolds number (Re) parameters on aerodynamic forces acting on the model. In computational fluid dynamics (CFD) study, the Reynolds Averaged Navier-Stokes (RANS) model was solved for steady flow. In the wind tunnel, drag/thrust coefficients were obtained by pressure measurements in the wake of the model using the Jones method. Direct measurements of aerodynamic forces were performed on force-balance mechanism. Tufts method was used to investigate flow separation on the model surface. According to the experimental results TSR has more effect on the aerodynamic force coefficients comparing with Reynolds number and larger TSR increases the thrust and lift coefficients. While lift coefficient decreases with increasing Reynolds number, thrust coefficient increases. For the fan-off condition, flow separation was observed on model upper surface close to trailing edge at high angle of attack (α) and Re values which disappeared for the fan-on and TSR value over 1 condition. Thrust coefficients obtained by CFD analysis for α = 0°, TSR = 1.4 and varying Reynolds numbers were within 12% of experimental results. [ABSTRACT FROM AUTHOR]

To find out the comprehensive principles of synthetic jet control effects on airfoil stall characteristics, fundamental contrastive wind-tunnel tests were conducted systematically. By using six-component balance, Particle Image Velocimetry (PIV) technology and boundary layer probe, the measurements of model aerodynamic forces, the whole velocity field over airfoil and velocity profiles in the boundary layer were conducted, respectively. Based upon the experimentally parametric analyses of synthetic jet control on airfoil, it is concluded that the incline angle of synthetic jet has an important impact on both the flow in boundary layer and aerodynamic forces of airfoil. A tangential jet inject energy and accelerate the velocity of flow in inner boundary layer thus has a better control effects on delay stall of airfoil when the momentum coefficient of jet is relatively large, and the normal jet helps to enlarge the thickness of boundary layer which is proved to have better control effects on flow separation control and improving the aerodynamic characteristics of airfoil when the momentum coefficient of a jet is relatively small. [ABSTRACT FROM AUTHOR]

The combined effects of percent slope and fire intensity of a wind driven line fire on an idealized building has been numerically investigated in this paper. The simulations were done using the large eddy simulation (LES) solver of an open source CFD toolbox called FireFOAM. A set of three fire intensity values representing different heat release rates of grassland fuels on different inclined fuel beds have been modeled to analyze the impact of factors, such as fuel and topography on wind-fire interaction of a built area. An idealized cubic structure representing a simplified building was considered downstream of the fire source. The numerical results have been verified with the aerodynamic measurements of a full-scale building model in the absence of fire effects. There is a fair consistency between the modeled findings and empirical outcomes with maximum error of 18%, which acknowledge the validity and precision of the proposed model. The results show that concurrent increase of fire intensity and terrain slope causes an expansion of the surface temperature of the building which is partially due to the increase of flame tilt angle upslope on the hilly terrains. In addition, increasing fire intensity leads to an increase in the flow velocity, which is associated with the low-pressure area observed behind the fire front. Despite limitations of the experimental results in the area of wind-fire interaction the result of the present work is an attempt to shed light on this very important problem of fire behavior prediction. This article is a primary report on this subject in CFD modeling of the collective effects of fire intensity and sloped terrain on wind driven wildfire and its interaction on buildings. [ABSTRACT FROM AUTHOR]

Land surface temperature (LST) is a preeminent state variable that controls the energy and water exchange between the Earth's surface and the atmosphere. At the landscape-scale, LST is derived from thermal infrared radiance measured using space-borne radiometers. In contrast, plot-scale LST estimation at flux tower sites is commonly based on the inversion of upwelling longwave radiation captured by tower-mounted radiometers, whereas the role of the downwelling longwave radiation component is often ignored. We found that neglecting the reflected downwelling longwave radiation leads not only to substantial bias in plot-scale LST estimation, but also have important implications for the estimation of surface emissivity on which LST is co-dependent. The present study proposes a novel method for simultaneous estimation of LST and emissivity at the plot-scale and addresses in detail the consequences of omitting down-welling longwave radiation as frequently done in the literature. Our analysis uses ten eddy covariance sites with different land cover types and found that the LST values obtained using both upwelling and downwelling longwave radiation components are 0.5–1.5 K lower than estimates using only upwelling longwave radiation. Furthermore, the proposed method helps identify inconsistencies between plot-scale radiometric and aerodynamic measurements, likely due to footprint mismatch between measurement approaches. We also found that such inconsistencies can be removed by slight corrections to the upwelling longwave component and subsequent energy balance closure, resulting in realistic estimates of surface emissivity and consistent relationships between energy fluxes and surface-air temperature differences. The correspondence between plot-scale LST and landscape-scale LST depends on site-specific characteristics, such as canopy density, sensor locations and viewing angles. Here we also quantify the uncertainty in plot-scale LST estimates due to uncertainty in tower-based measurements using the different methods. The results of this work have significant implications for the combined use of aerodynamic and radiometric measurements to understand the interactions and feedbacks between LST and surface-atmosphere exchange processes. [ABSTRACT FROM AUTHOR]

This study concerns the experimental characterization of trailing edge noise, the understanding of which is crucial for mitigating acoustic pollution across major industries. An aeroacoustic experiment is carried out using a closed-vein wind tunnel to investigate the laminar boundary layer vortex-shedding (LBL-VS) noise of a symmetric NACA0021 airfoil in low Reynolds number flows (Re ≤ 163,500). Steady aerodynamic and acoustic measurements are performed, with numerous conditions covered (flow velocity from 10 m/s to 24.5 m/s, airfoil incidence from −10° to 10°). The aerodynamic results reveal that, in the pre-stall regime, the airfoil' suction side exhibits both a laminar separation bubble (LSB) and a trailing edge detached flow – which both make LBL-VS noise likely to occur. The acoustic results reveal that, when at low speed and moderate incidence, the airfoil emits one to two tones, which can be both attributed to LBL-VS noise. In particular, their respective frequency is seen to scale as the 0.8th power of the flow velocity, whereas varying linearly with the incidence. At higher speeds, these two tones vanish to the profit of other, more intense tonal emissions, whose frequency does not scale with the velocity nor the incidence. These tones are attributed to resonance effects coming from a retroaction of the reverberant environment onto the LBL-VS noise emission, which then locks-on to some of the duct resonant frequencies via an acoustic feedback loop. Revealing indirectly the presence of the pre-existing LBL-VS noise, these resonant tones emerge only when the flow velocity and incidence obey specific conditions, namely a roughly linear relationship. [ABSTRACT FROM AUTHOR]

Combined measurement of shape and aerodynamic force is effective for understanding the mechanism of transonic wing flutter. To explore one method, a random-dot pressure-sensitive paint (PSP) was applied to the time-resolved global measurement of the deformation and pressure field of a transonic flow over an airfoil. The random-dot PSP has a patterned texture with luminescence intensity, which is made by intentional photodegradation of a PSP dye. These dots allow simultaneous measurement of pressure and the surface profile of the airfoil using stereo-digital image correlation. The feasibility of the random-dot PSP was tested in a transonic wind tunnel using a three-dimensional backswept wing model, which started to flutter at Mach 0.89 with a dominant frequency of 100 Hz. The unsteady surface profile and pressure distribution of the airfoil were measured using 12-bit high-speed cameras as the deformation amplitude increased. The experimental results indicate that the deformation and surface pressure distribution during flutter were successfully measured over time. The accuracy of the measured deformations and pressures was evaluated by comparison with several point data obtained with a laser displacement meter and semiconductor pressure transducers. The accuracy at each time-resolved image obtained at a recording rate of 6.25 kHz was within 1 mm for displacement and about 1 kPa for pressure. [ABSTRACT FROM AUTHOR]

Background: Glottal insufficiency, mostly caused by unilateral vocal fold paralysis (UVFP) or vocal fold atrophy can be treated by injection laryngoplasty (IL). Materials such as hyaluronic acid (HA) gels are now widely available and used to improve voice quality. Various durability and effects of HA injection laryngoplasties have been reported. The aim of this study is to provide a systematic review of the literature for the use of HA in injection laryngoplasties. Methods: A systematic literature search was conducted in PubMed and Cochrane Libraries. Three reviewers assessed original research studies concerning vocal fold augmentation with HA for eligibility. English written full-text human studies from 2000 to 2020 with EBM level 1b—2 were included. In vitro studies, animal studies, case reports, case–control studies, correspondence and review articles, and articles with other injection materials were excluded. Demographical data, indication, type of HA, evaluation methods, follow-up, durability of implanted material and complications were assessed. Results: A total number of 311 articles were found in PubMed and Cochrane Library, 13 studies were eligible for final analysis with 1063 patients, mean age of patients was 58.7 years. Main indication for HA IL was unilateral vocal fold paralysis, evaluation methods were subjective—VHI (Voice Handicap Index) questionnaire and objective—acoustic and aerodynamic measurements, mean time of follow-up was 5.9 months. Large-particle HA gels were more favorable for longer durability than small-particle HA, reported time of resorption of HA gels ranges between 6 and 12 months, and complication rate was low. Conclusion: Hyaluronic acid injection laryngoplasty increases voice quality, improves results of voice therapy, and can be recommended as overlap treatment before permanent medialization surgery. Compared to other injected materials, HA seems to have more favorable effect on vibratory functions of the vocal folds and thus on the voice quality parameters. [ABSTRACT FROM AUTHOR]

The existing moving vehicle models generally require a long test-track to realize the acceleration and deceleration processes and the negative effect of data cables is inevitably for the wind pressure measurement using the traditional pressure scanning system. To address the technical obstacle for moving vehicle models in wind tunnel tests, a new type of aerodynamic measurement technology is presented in this study. Firstly, a piece of new kinetic equipment, a U-Shaped launching ramp, is proposed. The U-Shaped launching ramp can realize the acceleration and deceleration of the vehicle model by gravity and makes full use of the test section of the wind tunnel. Then, a wireless pressure acquisition system is developed to virtually eliminate the negative effects of the inertia and friction forces. By comparing with the conventional wind pressure test data, the proposed wireless pressure acquisition system presents a higher accuracy and fully satisfies the test requirement for the moving vehicle-bridge system. From the scaled test, it is confirmed that the aerodynamic forces of the moving vehicle model are larger than that of the static one, implying that the moving test is necessary for studying the aerodynamic characteristics of the vehicle-bridge coupling system. [ABSTRACT FROM AUTHOR]

Global evaporation monitoring from Earth observation thermal infrared satellite missions is historically challenged due to the unavailability of any direct measurements of aerodynamic temperature. State‐of‐the‐art one‐source evaporation models use remotely sensed radiometric surface temperature as a substitute for the aerodynamic temperature and apply empirical corrections to accommodate for their inequality. This introduces substantial uncertainty in operational drought mapping over complex landscapes. By employing a non‐parametric model, we show that evaporation can be directly retrieved from thermal satellite data without the need of any empirical correction. Independent evaluation of evaporation in a broad spectrum of biome and aridity yielded statistically significant results when compared with eddy covariance observations. While our simplified model provides a new perspective to advance spatio‐temporal evaporation mapping from any thermal remote sensing mission, the direct retrieval of aerodynamic temperature also generates the highly required insight on the critical role of biophysical interactions in global evaporation research. Plain Language Summary: Water lost by plants through evaporation is strongly linked with the temperature at an unknown height within the canopy. Because this in‐canopy temperature cannot be typically measured by a satellite, the majority of the global evaporation models substitute this with skin temperature, or the near‐surface temperature observed by the satellite sensors. Such methods do not fully capture the physical and biological processes governing the magnitude and variability of plant water use under severe water stress, leading to substantial errors in water cycle monitoring in the dry regions. Here, we show how a simple model that requires no anticipated parameter, provides not only reasonable estimates of evaporation in a variety of dry and wet conditions, but also a better insight into the role of plant water stress and greenness in the difference between the in‐canopy temperature and skin temperature. This model offers an alternative and novel perspective that can be used in images from current and future thermal satellite missions to advance global plant water use mapping for several water management applications and to investigate the highly complex land‐atmosphere interactions and feedback mechanisms. Key Points: Aerodynamic temperature and evaporation well estimated from physical principles and available energy‐water limits in different ecosystemsWater stress and vegetation cover influences the difference between aerodynamic and radiometric temperatures through plant homeostasisNon‐parametric model offers a parameter‐sparse approach describing evaporation, canopy conductance and vapor pressure deficit relationship [ABSTRACT FROM AUTHOR]

Assessment of aerodynamic forces and heat-transfer rates for certain flight conditions is an essential task in designing a hypersonic vehicle. Experimental investigation of impulse ground-based type facilities is researchers standard practice for such purposes. However, due to extremely short test times of the flow, measurement of aerodynamic forces and heat-transfer rates in such facilities causes many technical issues. This study presents a series of drag and heat-flux measurements taken in the shock tunnel. An asymmetric blunt shaped forebody was tested at a nominal Mach 6. A conventional accelerometer-based drag balance system was applied to the test model during force measurements. K-type thermocouple sensors were used to measure surface heat-transfer rates. A comprehensive procedure for implementation and calibration of each measurement technique is provided in a single manuscript. [ABSTRACT FROM AUTHOR]

Experimental and numerical investigations were conducted to examine the influence of inlet incidence angle and squealer tip cutback on a turbine blade. The measurements of aerodynamic loss and tip heat transfer were performed under transonic conditions. Numerical models were established and validated using experimental data to gain insight into the underlying flow and thermal physics. The results demonstrate that as the incidence angle increases, the strength of TLV and UPV is significantly intensified, leading to a substantial increase in aerodynamic losses. Compared to the baseline case, a positive incidence angle of 7.5° can result in a 21.2% rise in the area-averaged TPL, while a negative incidence angle of −7.5° can reduce the area-averaged TPL by 3.2%. Moreover, the changes in incidence angle have a significant impact on the distribution of heat transfer within the tip cavity. Furthermore, a cutback squealer tip configuration was proposed and compared to a full squealer tip under a positive incidence condition. The results show that by implementing a tip cutback configuration, the leakage loss of the turbine blade can be reduced by 4.1%. Additionally, there were notable changes in tip heat transfer near the notched rim and trailing edge when employing the cutback tip. • The influence of inlet incidence on turbine tip aero-thermal performance is investigated experimentally and numerically. • The squealer tip cutback is introduced to reduce the tip leakage loss and tip heat transfer level. • The aerodynamic and heat transfer measurements are conducted in transonic conditions. • CFD simulations are conducted to gain insights into the flow and thermal physics of turbine tips. [ABSTRACT FROM AUTHOR]

Land surface temperature (LST) is a preeminent state variable that controls the energy and water exchange between the Earth's surface and the atmosphere. At the landscape-scale, LST is derived from thermal infrared radiance measured using space-borne radiometers. In contrast, plot-scale LST estimation at flux tower sites is commonly based on the inversion of upwelling longwave radiation captured by tower-mounted radiometers, whereas the role of the downwelling longwave radiation component is often ignored. We found that neglecting the reflected downwelling longwave radiation leads not only to substantial bias in plot-scale LST estimation, but also have important implications for the estimation of surface emissivity on which LST is co-dependent. The present study proposes a novel method for simultaneous estimation of LST and emissivity at the plot-scale and addresses in detail the consequences of omitting down-welling longwave radiation as frequently done in the literature. Our analysis uses ten eddy covariance sites with different land cover types and found that the LST values obtained using both upwelling and downwelling longwave radiation components are 0.5–1.5 K lower than estimates using only upwelling longwave radiation. Furthermore, the proposed method helps identify inconsistencies between plot-scale radiometric and aerodynamic measurements, likely due to footprint mismatch between measurement approaches. We also found that such inconsistencies can be removed by slight corrections to the upwelling longwave component and subsequent energy balance closure, resulting in realistic estimates of surface emissivity and consistent relationships between energy fluxes and surface-air temperature differences. The correspondence between plot-scale LST and landscape-scale LST depends on site-specific characteristics, such as canopy density, sensor locations and viewing angles. Here we also quantify the uncertainty in plot-scale LST estimates due to uncertainty in tower-based measurements using the different methods. The results of this work have significant implications for the combined use of aerodynamic and radiometric measurements to understand the interactions and feedbacks between LST and surface-atmosphere exchange processes. [ABSTRACT FROM AUTHOR]

The aerodynamic aerosol classifier (AAC) is a novel instrument that size-selects aerosol particles based on their mechanical mobility. So far, the application of an AAC for cloud condensation nuclei (CCN) activity analysis of aerosols has yet to be explored. Traditionally, a differential mobility analyzer (DMA) is used for aerosol classification in a CCN experimental setup. A DMA classifies particles based on their electrical mobility. Substituting the DMA with an AAC can eliminate multiple-charging artifacts as classification using an AAC does not require particle charging. In this work, we describe an AAC-based CCN experimental setup and CCN analysis method. We also discuss and develop equations to quantify the uncertainties associated with aerosol particle sizing. To do so, we extend the AAC transfer function analysis and calculate the measurement uncertainties of the aerodynamic diameter from the resolution of the AAC. The analysis framework has been packaged into a Python-based CCN Analysis Tool (PyCAT 1.0) open-source code, which is available on GitHub for public use. Results show that the AAC size-selects robustly (AAC resolution is 10.1, diffusion losses are minimal, and particle transmission is high) at larger aerodynamic diameters (≥∼ 85 nm). The size-resolved activation ratio is ideally sigmoidal since no charge corrections are required. Moreover, the uncertainties in the critical particle aerodynamic diameter at a given supersaturation can propagate through droplet activation, and the subsequent uncertainties with respect to the single-hygroscopicity parameter (κ) are reported. For a known aerosol such as sucrose, the κ derived from the critical dry aerodynamic diameter can be up to ∼ 50 % different from the theoretical κ. In this work, we do additional measurements to obtain dynamic shape factor information and convert the sucrose aerodynamic to volume equivalent diameter. The volume equivalent diameter applied to κ -Köhler theory improves the agreement between measured and theoretical κ. Given the limitations of the coupled AAC–CCN experimental setup, this setup is best used for low-hygroscopicity aerosol (κ≤0.2) CCN measurements. [ABSTRACT FROM AUTHOR]

The effective density is an essential physical property of atmospheric aerosols. The study of the effective density helps characterize the aerodynamic behavior of aerosol particles, providing vital information on the chemical composition, mixing state, and aging process of the particles. Size-resolved effective density measurements based on the Aerodynamic Aerosol Classifier–Scanning Mobility Particle Sizer (AAC–SMPS) tandem system were conducted in Beijing from March 10 to 31, 2023. This study analyzed the relationship between the aerodynamic diameter and effective density and the characteristics of the effective density under different pollution conditions. During the entire observation period, the average effective densities for the 150-, 250-, 350-, 450-, and 550-nm particles were 1.48 ± 0.07, 1.59 ± 0.08, 1.69 ± 0.09, 1.73 ± 0.09, and 1.75 ± 0.13 g/cm3, respectively, i.e., the effective density was highly particle size-dependent, exhibiting higher values at larger aerodynamic diameters. The size-resolved effective density under different pollution conditions differed and was related to the air mass variations. Under dusty conditions, the effective density of particles was highest under the influence of dust air masses from the northern areas. The effective density of small particles (150–350 nm) of the northern clean air masses was lower than that of the southern polluted air masses; however, the opposite was observed for large particles (450–550 nm). The diurnal effective density variation was generally more pronounced during daytime. Under both clean and dusty conditions, there was a sudden effective density decrease at 150 nm during the evening peak traffic. Under the influence of new particle formation (NPF) events, a significant effective density decrease was observed when the accumulation mode began to grow. Size-resolved effective density under different pollution conditions during the measurement period. [Display omitted] • The relationship between aerodynamic diameter and effective density was established using the AAC-SMPS tandem system. • The effective density of 150–550 nm particles significantly increased with increasing aerodynamic diameter. • Aerosol size-resolved effective density during different pollution conditions was analyzed. • The evolution of effective density under the influence of NPF events was analyzed. [ABSTRACT FROM AUTHOR]

The Aerodynamic Aerosol Classifier (AAC) is a novel instrument that size-selects aerosol particles based on their mechanical mobility. So far, the application of an AAC for Cloud Condensation Nuclei (CCN) activity analysis of aerosols has yet to be explored. Traditionally, a Differential Mobility Analyzer (DMA) is used for aerosol classification in a CCN experimental setup. A DMA classifies particles based on their electrical mobility. Substituting the DMA with an AAC can eliminate multiple charging artefacts as classification using an AAC does not require particle charging. In this work, we describe an AAC-based CCN experimental setup and CCN analysis method. We also discuss and develop equations to quantify the uncertainties associated with aerosol particle sizing. To do so, we extend the AAC transfer function analysis and calculate the measurement uncertainties of the aerodynamic diameter from the resolution of the AAC. The analyses framework has been packaged into a Python-based CCN Analysis Tool (PyCAT 1.0) open source code, which is available on GitHub for public use. Results show that the AAC size-selects robustly (AAC resolution is 10.1, diffusion losses are minimal and particle transmission is high) at larger aerodynamic diameters (= ~85nm). The size-resolved activation ratio is ideally sigmoidal since no charge corrections are required. Moreover, the uncertainties in the critical particle aerodynamic diameter at a given supersaturation can propagate through droplet activation and the subsequent uncertainties with respect to the single-hygroscopicity parameter (?) are reported. For a known aerosol such as sucrose, the ? derived from the critical dry aerodynamic diameter can be up to ~50% different from the theoretical ?. In this work, we do additional measurements to obtain dynamic shape factor information and convert the sucrose aerodynamic to volume equivalent diameter. The volume equivalent diameter applied to ?- Köhler theory improves the agreement between measured and theoretical ?. Given the limitations of the coupled AAC-CCN experimental setup, this setup is best used for low hygroscopicity aerosol (?=0.2) CCN measurements. [ABSTRACT FROM AUTHOR]

Aerodynamic loads of wind turbine blades are often predicted by manufacturers using the blade element momentum (BEM) theory, for which many corrections have been proposed in the literature. The physical impacts of such corrections on field measurements have seldom been assessed because of the relative unavailability of dedicated measurements. Based on the unique full‐scale database of the DANAERO project, available through the IEA (International Energy Agency) Task 29, this work incrementally applies on aerodynamic field measurement improvements of the BEM theory: atmospheric boundary layer vertical velocity gradient, neighboring wake, yaw misalignment, wind inflow location, tower shadow effect, cone angles modeling, blade aeroelastic deformation, and dynamic wake. This is performed using the iBEM method (inverse Blade Element Momentum), which back‐calculates the aerodynamic coefficients (lift—CL and drag—CD) using aerodynamic loads from field tests. [ABSTRACT FROM AUTHOR]

The objective of this study is to determine the two-dimensional unsteady aerodynamic forces and moment acting on a heaving wing in a uniform flow using a wind tunnel. However, it is difficult to measure the aerodynamic forces acting on the heaving wing due to measuring device oscillation and the large inertial force of the wing model. In this study, a new type of wind tunnel test, named "heaving wind tunnel," was developed. Here, the wing model remains stationary as the wind tunnel oscillates with a heaving motion. The advantage of this experimental method is that the measurement results are unaffected by the large inertial force acting on the oscillating wing model. Therefore, the wing model can be used in the same way as in steady state experiments. The normal force, thrust and pitching moment coefficients of a heaving airfoil were measured using the heaving wind tunnel test developed in this study. Through flow visualizations and pressure measurements, we found that the rapid drop in normal force coefficient after it reached its maximum value was due to a large growing leading-edge vortex. [ABSTRACT FROM AUTHOR]

Semi-occluded vocal tract exercises (SOVTEs) are increasingly popular as therapeutic exercises for patients with voice disorders. This popularity is reflected in the growing research literature, investigating the scientific principles underlying SOVTEs and their practical efficacy. This study examines several acoustic, articulatory, and aerodynamic variables before, during, and after short-duration (15 s) SOVTEs with a narrow tube in air. Participants were 20 healthy young adults, and all variables were measured at threshold phonation levels. Acoustic variables were measured with a microphone and a neck accelerometer, and include fundamental frequency, glottal open quotient, and vocal efficiency. Articulatory variables were measured with ultrasound, and include measures of the tongue tip, tongue dorsum, and posterior tongue height, and horizontal tongue length. Aerodynamic variables were measured with an intraoral pressure transducer and include subglottal, intraoral, and transglottal pressures. Lowering of the posterior tongue height and tongue dorsum height were observed with gender-specific small changes in the fundamental frequency, but there were no significant effects on the transglottal pressure or vocal efficiency. These findings suggest that the voices of healthy young adults already approach optimal performance, and the continued search for scientific evidence supporting SOVTEs should focus on populations with voice disorders. [ABSTRACT FROM AUTHOR]

The Satellite for Orbital Aerodynamics Research (SOAR) is a CubeSat mission, due to be launched in 2021, to investigate the interaction between different materials and the atmospheric flow regime in very low Earth orbits (VLEO). Improving knowledge of the gas–surface interactions at these altitudes and identification of novel materials that can minimise drag or improve aerodynamic control are important for the design of future spacecraft that can operate in lower altitude orbits. Such satellites may be smaller and cheaper to develop or can provide improved Earth observation data or communications link-budgets and latency. In order to achieve these objectives, SOAR features two payloads: (i) a set of steerable fins which provide the ability to expose different materials or surface finishes to the oncoming flow with varying angle of incidence whilst also providing variable geometry to investigate aerostability and aerodynamic control; and (ii) an ion and neutral mass spectrometer with time-of-flight capability which enables accurate measurement of the in-situ flow composition, density, velocity. Using precise orbit and attitude determination information and the measured atmospheric flow characteristics the forces and torques experienced by the satellite in orbit can be studied and estimates of the aerodynamic coefficients calculated. This paper presents the scientific concept and design of the SOAR mission. The methodology for recovery of the aerodynamic coefficients from the measured orbit, attitude, and in-situ atmospheric data using a least-squares orbit determination and free-parameter fitting process is described and the experimental uncertainty of the resolved aerodynamic coefficients is estimated. The presented results indicate that the combination of the satellite design and experimental methodology are capable of clearly illustrating the variation of drag and lift coefficient for differing surface incidence angle. The lowest uncertainties for the drag coefficient measurement are found at approximately 300 km, whilst the measurement of lift coefficient improves for reducing orbital altitude to 200 km. • The design of the experimental CubeSat SOAR (Satellite for Orbital Aerodynamics) is presented. • SOAR is due to be launched in early 2021 to the ISS and subsequently deployed into orbit. • The mission will perform the aerodynamic characterisation of materials in very low Earth orbit (VLEO). • The aim is to improve understanding of the fundamental gas–surface interactions in the VLEO environment. • Materials able to reduce aerodynamic drag and improve aerodynamics-based control will be tested. [ABSTRACT FROM AUTHOR]

A new Pressure Sensitive Paint (PSP) has been developed to map pressure distribution on surfaces of building models during aerodynamic tests in wind tunnel. The PSP consists of 2-hydroxyethyl acrylate (HEA) hydrogel matrix and ethyl eosin (EE) as a fluorescent pressure sensor. First, the spectroscopic properties and photostability of the PSP were investigated. The maximum coating thickness was determined to be 3 mm. The PSP system was studied in the Constant-Thickness-Mode (CTM) and Variable-Thickness-Mode (VTM). It was found that fluorescence intensity of the PSP decreased with increasing pressure. Under CTM conditions, the EE-based PSP system behaved like a classic Solvent-Quenched Pressure Sensitive Paint (SQ-PSP). Its sensitivity to changes of pressure was about 35 %/bar, which is comparable to the sensitivity of SQ-PSPs based on europium complexes and sensitivity of Oxygen Quenched Pressure Sensitive Paints (OQ-PSP). However, under VTM conditions, the sensitivity of the PSP studied turned out to be about 50 times higher than that in CTM mode, due to simultaneous solvent quenching of EE sensor and change of the paint thickness upon pressure, while the effect of thickness change on fluorescence intensity was dominating. Next, pressure distribution on the side wall surface of a building model at different angles of inclination to the wind direction was mapped using classic pressure taps (as a reference) and the new PSP system in VTM mode. It has been found that the pressure maps obtained using the new PSP system are consistent with those obtained using pressure taps in the overpressure area, but show some differences in the under-pressure area, which confirms that the new PSP system can be used for aerodynamic tests under certain conditions. [Display omitted] • A new type of polymeric pressure-sensitive material for the role of Pressure Sensitive Paints, it is possible to apply such sensory systems to low-pressure aerodynamic tests of building structures. • The Pressure Sensitive Paints described in this work are based on a polymer hydrogel matrix and are more sensitive around atmospheric pressure than currently known sensory materials. • Due to the solvent content in these matrices, they operate based on a completely different mechanism from the currently used in Pressure Sensitive Paints, which is solvent quenching of luminescence. • The research described the process of the design, preparation, spectroscopic characterization, and use of advanced intelligent polymeric sensory materials with information about a paradigm for future studies of the evolution of SQ-PSP systems. [ABSTRACT FROM AUTHOR]

The aerodynamic characteristics of a wing in a propeller slipstream were investigated at a low Reynolds number. The effects of propeller position and rotation direction on the wing were clarified by aerodynamic measurements and particle image velocimetry. The propeller positions were the center and tip of the wing model, whereas the rotation directions were clockwise and counterclockwise. The center propeller configuration with a clockwise rotation showed a constant pitching moment and increased the lift-to-drag ratio. This was caused by the high-speed propeller slipstream (i.e. 12 and 10m/s on the upwash and downwash sides, respectively) and the wingtip vortex effect on the slipstream separation. The separation point at an angle-of-attack of 18° was delayed from x/c µ 0.1 to 0.3 by the wingtip vortex. Hence, the following two factors must be considered to enhance the aerodynamic characteristics of a Mars airplane: (i) the ratio of the area of the upwash and downwash sides of a wing in a propeller slipstream, and (ii) the effect of the wingtip vortex on the propeller slipstream. [ABSTRACT FROM AUTHOR]

In this study, we investigated the performance of flexible trailing edge serrations of various shapes for airfoil self-noise reduction through anechoic wind tunnel experiments. A flat plate model was tested at zero angle of attack. The chord-based Reynolds number was between 1.6 × 105 and 4 × 105. The boundary layers were fully tripped near the leading edge. Add-on type trailing edge serrations were cut from flexible polyethylene terephthalate sheets. It is observed that compared with rigid serrations, flexible serrations can achieve an additional broadband noise reduction up to 2 dB–3 dB at high frequencies, and the effect also depends on the geometry of the serrations. Complementary deformation measurement and aerodynamic force measurement show that flexible serrations can align better with the flow and are expected to reduce the crossflow intensity near the serration roots, which has been related to the extraneous high-frequency noise generated by serrations in previous studies. An inviscid model is proposed to predict the wake structure and the loadings for serrations of various shapes. Although the model over-predicts the crossflow speed due to the omission of the viscous effect, the relative intensity corresponding to different serration geometry is consistent with experimental observations. Last, we show that the recent analytical noise prediction model [B. Lyu and L. J. Ayton, "Rapid noise prediction models for serrated leading and trailing edges," J. Sound Vib. 469, 115136 (2020)] for a serrated trailing edge still significantly overpredicts the noise reduction capacity by serrations and does not reveal the role of serration shape properly. This indicates the necessity to include the non-frozen turbulent properties near serrations in the future prediction models. [ABSTRACT FROM AUTHOR]

Multi-hole probe mounted on an aircraft provide the air velocity vector relative to the aircraft, requiring knowledge of the aircraft spatial orientation, translation, and velocity to translate this information to an Earth-based reference frame and determine the wind vector. As the relative velocity of the aircraft is typically an order of magnitude higher than the wind velocity, the extracted wind velocity is very sensitive to multiple sources of error including misalignment of the probe and aircraft coordinate system axes, sensor error and misalignment in time of the probe and aircraft orientation measurements in addition to aerodynamic distortion of the velocity field by the aircraft. Here, we present an approach which can be applied after a flight to identify and correct biases which may be introduced into the final wind measurement. The approach was validated using a ground reference, different aircraft, and for the same aircraft at different times. The results indicate significant reduction in wind velocity variance at frequencies which correspond to aircraft motion. [ABSTRACT FROM AUTHOR]