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The significance of this study involves the optimisation of the aeration efficiency (AE) of the venturi aerator using an artificial neural network (ANN) technique integrated with an optimisation algorithm, i.e., particle swarm optimisation (PSO) and genetic algorithm (GA). To optimise the effects of operational factors on aeration efficiency by utilising a venturi aeration system, aeration experiments were conducted in an experimental tank with dimensions of 90 cm × 55 cm × 45 cm. The operating parameters of the venturi aerator include throat length (TL), effective outlet pipe (EOP), and flow rate (Q) to estimate the efficacy of the venturi aerator in terms of AE. A 3-6-1 ANN model was developed and integrated with the PSO and GA techniques to find out the best possible optimal operating variables of the venturi aerator. The coefficient of determination (R²), root mean square error (RMSE), and mean absolute error (MAE) determined from the experimental and estimated data were used to assess and compare the performance of the ANN-PSO and ANN-GA modelling. It is shown that ANN-PSO provides a better result as compared to ANN-GA. The operational parameters, TL, EOP, and Q, were determined to have the most optimum values at 50 mm, 6 m, and 0.6 L/s, respectively. The optimised aeration efficiency of the venturi was found to be 0.105 kg O2/kWh at optimum operational circumstances. In fact, the neural network having an ideal design of (3-6-1) and a correlation coefficient value that is extremely close to unity has validated the results indicated above. [ABSTRACT FROM AUTHOR]

The development of civil construction technology in Indonesia is progressing along with the rise in high-rise building construction. The emergence of high-rise buildings has altered wind flow characteristics, leading to phenomena that can directly impact surrounding structures. One of the observable phenomena is the wind speed amplification caused by the narrowing of the wind flow section, known as the Venturi effect. This study aims to compare the outcomes of two Computational Fluid Dynamics (CFD) methods--Reynolds-Averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES)--against experimental results. The study employs a model of four buildings of similar height and symmetrical positioning, with a 72 mm passage width, to verify numerical simulations against experimental data. The RANS method yields a maximum wind speed amplification of 14.9% along the passage's centerline, which remains below the experimental prediction of 25.5% in Zone A. Conversely, the LES results show a higher wind speed amplification, reaching 40.2%, surpassing the experimental findings. Nevertheless, LES identifies a similar location for wind speed amplification observed in Zone A. Additionally, CFD simulations were conducted to analyze the effects of passage width, revealing that a passage width of 54 mm produces the highest wind speed amplification, with a ratio value of passage width to building influence scale (L/S) of 0.481. Further research on building model scale may be necessary to verify CFD accuracy compared to the actual scale. However, such simulations demand exceedingly high computational resources with current technology. [ABSTRACT FROM AUTHOR]

This paper contributes to a new Lagrangian vortex method for the statistical control of turbulence in two-dimensional flow configurations around a rough circular cylinder in ground effect when considering higher subcritical Reynolds numbers, namely 3 × 104 ≤ Re ≤ 2 × 105. A smoothed moving wall (active control technique) is used to include the blockage effect in association with the variation in cylinder surface roughness (passive control technique), characterizing a hybrid approach. In contrast with the previous approaches of our research group, the rough cylinder surface is here geometrically constructed, and a new momentum source term is introduced and calculated for the investigated problem. The methodology is structured by coupling the random Discrete Vortex Method, the Lagrangian Dynamic Roughness Model, and the Large Eddy Simulation with turbulence closure using the truncated Second-Order Velocity Structure Function model. This methodological option has the advantage of dispensing with the use of both a refined near-wall mesh and wall functions. The disadvantage of costly processing is readily solved with Open Multi-Processing. The results reveal that intermediate and high roughness values are most efficient for Reynolds numbers on the orders of 105 and 104, respectively. In employing a moving wall, the transition from the large-gap to the intermediate-gap regime is satisfactorily characterized. For the conditions studied with the hybrid technique, it was concluded that the effect of roughness is preponderant and acts to anticipate the characteristics of a lower gap-to-diameter ratio regime, especially with regard to intermittency. [ABSTRACT FROM AUTHOR]

The purpose of aeration in water is to transfer or remove gases from the water. Dissolved oxygen is critical for living life. In water engineering, aeration and oxygen transfer using water jets are common. In this study, various venturi nozzles with air holes in the throat portion were manufactured and meaningful experiments were conducted to determine their oxygen transfer efficiency and aeration performance., the venturi nozzles with throat diameters 14, 17 and 20 mm were used in the experimental study. The ratio of the diameter of the air holes to the diameter of the throat portion is taken as 0.1, 0.2 and 0.3. Different experiments were carried out for nine different hole diameters. In addition, the ratio of the throat portion length to the throat portion diameter was taken as 1.00 and 0.50. For all nozzles, the ratio of outlet length to outlet diameter was taken as 1 and 2. In addition, comprehensive experiments were carried out for a venturi, considering the ratio of outlet length to outlet diameter as 1, 2, 3, 4 and 5. The experiments were also conducted for the circular nozzle to make comparisons. In this study, venturi nozzles gave better results than circular nozzles, and higher aeration performance values were obtained for the ratios 0.2 and 0.3, 1, 0.50 and 0.50. It was found that the aeration performance of the venturi nozzle was approximately 6.5 times higher than the air entrainment rate performance of the circular nozzle and 2.5 times higher in terms of oxygen transfer. [ABSTRACT FROM AUTHOR]

The INVELOX system is an innovative approach that offers improved energy absorption efficiency from wind flow and reduced costs by utilizing smaller wind turbines. This research focuses on investigating the steady-state performance of one, two, or three wind turbines arranged within the venturi section of the system. A comprehensive modeling approach using an improved Blade Element Momentum (BEM) theory is proposed and implemented as a MATLAB code. The code incorporates Prandtl's tip and hub loss factors, as well as turbulent wake corrections. The accuracy of the code is validated against experimental and numerical data. The results demonstrate that in a three-rotor tandem configuration in the INVELOX system, the power extracted from the second and third turbines is 0.54 and 0.24 times the power of the first turbine, respectively. Furthermore, for a two-turbine arrangement in the venturi section, the total power extracted from the system is 53.9% higher than that of a single turbine layout. In the case of a three-turbine configuration, the total power increases up to 1.78 times compared to a single turbine. The proposed model is suitable for geometric optimization and parameter studies. The system's performance is evaluated in terms of tip speed ratio, and the effects of different correction models are analyzed, including the local changes in forces and moments. [ABSTRACT FROM AUTHOR]

Abstract Introduction Ventricular septal defect (VSD) is one of the most common congenital cardiac anomalies. Patients with perimembranous VSD may have aortic regurgitation (AR) secondary to prolapse of the aortic cusp. Case presentation We present a case of 23-year-old White man with VSD, AR and ascending aortic aneurysm. The patient presented to outpatient clinic with weakness and gradual worsening shortness of breath for the past 5 years. Clinical examination revealed regular heart rhythm and loud continuous systolic-diastolic murmur (Lewin’s grade 6/6), heard all over the precordium, associated with a palpable thrill. The ECG showed right axis deviation, fractionated QRS in V1 and signs of biventricular hypertrophy. The chest X-ray showed cardiomegaly. Transthoracic and transesophageal echocardiograms showed a perimembranous VSD with moderate restrictive shunt (Qp/Qs = 1.6), aortic regurgitation (AR), and ascending aortic aneurysm. Other clinical and laboratory findings were within normal limits. Conclusions Perimembranous VSD, may be associated with aortic regurgitation and ascending aortic aneurysm as secondary phenomenon if it is not early diagnosed and successfully treated.

Spinal arachnoid web (SAW) is a rare disease entity characterized as band-like arachnoid tissue that can cause spinal cord compression and syringomyelia. This study aimed to analyze the surgical management of the spinal arachnoid web in patients with syringomyelia, focusing on surgical strategies and outcomes. A total of 135 patients with syringomyelia underwent surgery at our department between November 2003 and December 2022. All patients underwent magnetic resonance imaging (MRI), with a special syringomyelia protocol (including TrueFISP and CINE), and electrophysiology. Among these patients, we searched for patients with SAW with syringomyelia following careful analysis of neuroradiological data and surgical reports. The criteria for SAW were as follows: displacement of the spinal cord, disturbed but preserved CSF flow, and intraoperative arachnoid web. Patients were evaluated for initial symptoms, surgical strategies, and complications by reviewing surgical reports, patient documents, neuroradiological data, and follow-up data. Of the 135 patients, 3 (2.22%) fulfilled the SAW criteria. The mean patient age was 51.67 ± 8.33 years. Two patients were male, and one was female. The affected levels were T2/3, T6, and T8. Excision of the arachnoid web was performed in all cases. No significant change in intraoperative monitoring was noted. Postoperatively, none of the patients presented new neurological symptoms. The MRI 3 months after surgery revealed that the syringomyelia improved in all cases, and caliber variation of the spinal cord could not be detected anymore. All clinical symptoms improved. In summary, SAW can be safely treated by surgery. Even though syringomyelia usually improves on MRI and symptoms also improve, residual symptoms might be observed. We advocate for clear criteria for the diagnosis of SAW and a standardized diagnostic (MRI including TrueFISP and CINE). [ABSTRACT FROM AUTHOR]

This article will outline the physics of gases relevant to anaesthetic practice. It will introduce the theory related to the states of matter, the ideal gas and the gas laws before discussing the factors that affect gas flow. Finally, it will explain the Bernoulli principle, Venturi effect and Coanda effect and their relevance to clinical practice. [ABSTRACT FROM AUTHOR]

Introduction: Ventricular septal defect (VSD) is one of the most common congenital cardiac anomalies. Patients with perimembranous VSD may have aortic regurgitation (AR) secondary to prolapse of the aortic cusp. Case presentation: We present a case of 23-year-old White man with VSD, AR and ascending aortic aneurysm. The patient presented to outpatient clinic with weakness and gradual worsening shortness of breath for the past 5 years. Clinical examination revealed regular heart rhythm and loud continuous systolic-diastolic murmur (Lewin's grade 6/6), heard all over the precordium, associated with a palpable thrill. The ECG showed right axis deviation, fractionated QRS in V1 and signs of biventricular hypertrophy. The chest X-ray showed cardiomegaly. Transthoracic and transesophageal echocardiograms showed a perimembranous VSD with moderate restrictive shunt (Qp/Qs = 1.6), aortic regurgitation (AR), and ascending aortic aneurysm. Other clinical and laboratory findings were within normal limits. Conclusions: Perimembranous VSD, may be associated with aortic regurgitation and ascending aortic aneurysm as secondary phenomenon if it is not early diagnosed and successfully treated. [ABSTRACT FROM AUTHOR]

Suction devices are integral to the safe delivery of anaesthesia and critical care. They are involved in clearing and aspirating body fluids, blood and debris, as well as employed in scavenging waste gases and diathermy fumes, intraoperative cell salvage systems, and tertiary devices such as vacuum mattresses and specialized wound dressings. All suction devices require three essential components, namely a source of vacuum, a reservoir/collection vessel and suction tubing. Other components of a suction device include an on/off switch, a vacuum regulator, vacuum gauge, filters, an overflow safety trap, an overfill protection device in the collection vessel, and a catheter. Several different types of catheter are available for use in different clinical situations. Vacuum and flow are the main physical principles underlying suction devices. The source of vacuum may be a fixed centrally piped system or a portable device using electrical, pneumatic or manual power. Pneumatically powered suction devices utilize the Bernoulli principle and Venturi effect. The efficiency of each system depends upon principles of displacement, degree of negative pressure and time taken to reach this, the internal resistance of the suction apparatus and the viscosity of the material to be aspirated. [ABSTRACT FROM AUTHOR]

HVAC industry is one of the fastest-rising contributors to global warming, therefore, innovative change is necessary to open the door for the investigation of renewable energy sources that can be incorporated into HVAC systems and shift the emphasis to better environmental maintenance. Therefore, the goal of this study is to close this gap by creating an eco-cooler system that can offer exceptional cooling comfort while utilizing only renewable energy sources and having minimal environmental impact. The principle of the venturi effect, which is the primary element facilitating air cooling for the device, served as the foundation for the design and construction of the eco-cooler system. To obtain a more accurate assessment of the model, experimental analysis was carried out. Air temperature dropped between 4 and 8 °C due to the venturi effect phenomenon, and an additional 8 to 12 °C dropped as a result of evaporation. The water temperature at the evaporative pad was successfully lowered by about 4 °C using the PCM solution. According to this, the designed eco-cooler can transform air that is 30°C and 55% relative humidity at 13 mph into 18°C and 61% RH. [ABSTRACT FROM AUTHOR]

This paper contributes to a new Lagrangian vortex method for the statistical control of turbulence in two-dimensional flow configurations around a rough circular cylinder in ground effect when considering higher subcritical Reynolds numbers, namely 3 × 104 ≤ Re ≤ 2 × 105. A smoothed moving wall (active control technique) is used to include the blockage effect in association with the variation in cylinder surface roughness (passive control technique), characterizing a hybrid approach. In contrast with the previous approaches of our research group, the rough cylinder surface is here geometrically constructed, and a new momentum source term is introduced and calculated for the investigated problem. The methodology is structured by coupling the random Discrete Vortex Method, the Lagrangian Dynamic Roughness Model, and the Large Eddy Simulation with turbulence closure using the truncated Second-Order Velocity Structure Function model. This methodological option has the advantage of dispensing with the use of both a refined near-wall mesh and wall functions. The disadvantage of costly processing is readily solved with Open Multi-Processing. The results reveal that intermediate and high roughness values are most efficient for Reynolds numbers on the orders of 105 and 104, respectively. In employing a moving wall, the transition from the large-gap to the intermediate-gap regime is satisfactorily characterized. For the conditions studied with the hybrid technique, it was concluded that the effect of roughness is preponderant and acts to anticipate the characteristics of a lower gap-to-diameter ratio regime, especially with regard to intermittency.

The article focuses on the principles of fluid mechanics in anaesthetic practice, particularly Bernoulli's principle and the Venturi effect. Topics include the application of Bernoulli's principle in explaining fluid behavior, the derivation and application of Bernoulli's equation, and the role of the Venturi effect in clinical devices such as HAFOE devices.

The quality of wine is checked both during the production process and upon consumption. Therefore, manual wine-tasting work is still valuable. Due to the nature of wine, many volatile components are released, and it is therefore difficult to determine which elements need to be controlled. Acetic acid is one of the substances found in wine and is a crucial substance for wine quality. Gas sensor systems may be a potential alternative for manual wine tasting. In this work, we have developed a TGS2620 gas sensor module to analyze acetic acid levels in red wine. The gas sensor module was refined according to the Venturi effect along with signal slope analysis, providing promising results. The example included in this paper demonstrates that there is a direct relationship between the slope of the MOS gas sensor response and the acetic acid concentration. This relationship is useful to evaluate the ethanol oxidation in acetic acid in red wine during its production process. [ABSTRACT FROM AUTHOR]

Copyright of Atomic Energy Science & Technology is the property of Editorial Board of Atomic Energy Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The MODKARST mathematical code is used to simulate both brackish and non-brackish karst springs and provides useful information on the hydrological and hydrogeological characteristics of their aquifers. Next to this, MODKARST can also explain the often peculiar behavior of these springs, inherited from the complexity of the structures that most of the times form fractures, cavities, and conduits in carbonate formations in tectonically complex areas. The simulation focuses on explaining the complex behavior of the Azmak spring. Azmak is a large brackish karst spring in SW Turkey, which displays peculiarities both in terms of its hydrograph and seawater intrusion mechanism. In particular, during the recession period, contrary to the chloride concentrations of its water which appears more or less stable, its hydrograph shows fluctuations. The MODKARST simulation showed that the discharge fluctuation during the recession period is due to the operation of a siphon, while the abnormal variation of its chloride content is due to its predominant seawater intrusion mechanism which is the Venturi effect. [ABSTRACT FROM AUTHOR]

Venturi aeration is an economical method to increase dissolved oxygen (DO) in aquatic water bodies. For this paper, aeration experiments were conducted with 200 litres volume of the water tank, having dimensions of 90 cm length, 55 cm breadth, and 45 cm depth. The venturi was fabricated keeping the dimension of converging and diverging length same, i.e., 76 mm and throat length of 100 mm. The venturi aeration system was operated with six different discharge rates (0.00025, 0.00033, 0.00042, 0.00050, 0.00058 and 0.00067 m3/s). This work is intended to estimate the effect of varying discharges on the efficiency of venturi aerator in terms of standard oxygen transfer rate (SOTR) and standard aeration efficiency (SAE). The experiment shows promising results in terms of SOTR and SAE at moderate to high discharge rates, on the other hand a declining trend is seen when the liquid discharge rate is too high. The oxygen transfer rate was found to have a good relationship with the discharge rate. [ABSTRACT FROM AUTHOR]

The present research work deals with the design and fabrication of windmill using venturi effect. The venturi effect is achieved such a way that the propeller rotation is increased about four times for the wind velocity in the surroundings. For any direction of wind flow, the propeller is rotated. The wind velocity required for power production in our research area is very less when compared with the existing systems. There are no effects on the birds and also there is reduction in noise level when compared with existing conventional wind mills. The wind enters the nozzle where its velocity is increased slightly. Hence the proposed idea is to overcome the difficulties in exisisting wind mills. From this experimental analysis it was understood that the maximum yield of power was increased by 12% nearly (800 to 1000 W) compared to conventional windmills, which can be used essentially for domestic applications. The design in terms of cost and life was to be increased by 6% as compared to VAWT and HAWT. By the utilization of venturi wind turbines; the possibilities of facing real time problems such as resonance and sound intensity was decresed by 10% as compared to conventional wind turbines. [ABSTRACT FROM AUTHOR]

Coil migration is a known complication of endovascular coiling of cerebral aneurysms. We report an acute coil migration occurring during coiling of an unruptured anterior choroidal aneurysm, while a separate coil was retrieved into the microcatheter concomitantly without direct contact between the coils. The "pulling" of a previously deployed stable coil is presented as an adverse effect that should be noted. This case exemplifies that not only direct entanglement or erroneous malposition can generate acute migration, but possibly, also alteration of physical forces during coil retrieval. A potential mechanism, similar to a venturi effect, caused by a quick suction within the microcatheter at its distal end, is suggested, and the clinical relevance of the case is discussed. [ABSTRACT FROM AUTHOR]

Purpose: Pulmonary administration of dry drug powder is a considered promising strategy in the treatment of various lung diseases such as tuberculosis and is more effective than systemic medication. However, in the pre-clinical study phase, there is a lack of devices for effective delivery of dry powders to the lungs of small rodents. In this study, an administration device which utilizes Venturi effect to deliver dry powders to the lungs homogeneously was developed. Methods: A Venturi-effect administration device which synchronizes with breathes by use of a ventilator and aerosolizes the dry powders was created. Pulmonary distribution of inhalable dry powders prepared by spray-drying poly(lactic-co-glycolic) acid and an antituberculosis agent rifampicin and anti-tuberculosis effect of the powders on mycobacteria infected rats by administration with the Venturi-effect administration device and a conventional insufflation device were evaluated. Results: Homogeneous distribution of the dry powders in the lung was achieved by the Venturi-effect administration device due to efficient and recurring aerosolization of loaded dry powders while synchronizing with breathes. Amount of rifampicin delivered to the lungs by the Venturi-effect administration device was three times higher than that by a conventional insufflation device, demonstrating three times greater antimycobacterial activity. Conclusions: The Venturi-effect administration device aerosolized inhalable antituberculosis dry powders efficiently, achieved uniform pulmonary distribution, and aided the dry powders to exert antituberculosis activity on lung-residing mycobacteria. [ABSTRACT FROM AUTHOR]

The quality of wine is checked both during the production process and upon consumption. Therefore, manual wine-tasting work is still valuable. Due to the nature of wine, many volatile components are released, and it is therefore difficult to determine which elements need to be controlled. Acetic acid is one of the substances found in wine and is a crucial substance for wine quality. Gas sensor systems may be a potential alternative for manual wine tasting. In this work, we have developed a TGS2620 gas sensor module to analyze acetic acid levels in red wine. The gas sensor module was refined according to the Venturi effect along with signal slope analysis, providing promising results. The example included in this paper demonstrates that there is a direct relationship between the slope of the MOS gas sensor response and the acetic acid concentration. This relationship is useful to evaluate the ethanol oxidation in acetic acid in red wine during its production process.

Common topknots (Zeugopterus punctatus) attach to vertical rock surfaces and overhangs. It has been speculated that attachment is by a suction cup, with the median (anal, dorsal) fins providing a peripheral seal. Here the authors propose that the attachment is actually based on a Venturi effect. The rear portions of the median fins continually move in a fan‐like fashion (at c. 4 cycles per second). This movement produces a tailward fluid flow that ventilates the shallow underbody space between the fish and its rocky substratum. The anterior portions of the median fins seal the space laterally, but the space is open anterior (beneath the raised head) and posterior to the sea. The mid‐underbody space likely has a lower cross‐sectional area than does the front intake or rear exit, so flow should be faster (and pressure lower) within it than outside, thus providing pressure gradient suction. Topknots attach to rough and heavily biofouled surfaces, presumably because the high numbers of fin rays and their associated membranes plus fine muscle control allow effective sealing. The attachment ability is shared by all members of the flatfish tribe Phrynorhombini; it can be related to anatomical peculiarities and constitutes a probable synapomorphy for this clade. [ABSTRACT FROM AUTHOR]

Wind energy is foreseen to represent one of the most important drivers in the transition to a clean energy system. On one hand, the major trend is to increase the turbines' height and rotor size so as to improve the economy of scale. On the other hand, another approach that is receiving large interest is the so-called Ducted Wind Turbines that allows to significantly improve the turbines performance with reduced dimensions aiming at designing systems that could be integrated in the urban environment. This paper studies the optimal configuration of a mini- Ducted Wind Turbine by analysing, through numerical simulation and critical discussions, several different configurations varying the most critical geometric features of the system. The impact of such changes is analysed at varying wind speed and direction so as to also test the omnidirectionality of the system. Results of the final model are then compared with a similar turbine installed in open field showing that thanks to the mini Ducted Wind Turbine system is possible to exploit up to 432% more energy than a traditional system. Nevertheless, the final system still does not present a full omnidirectionality as it experiences an inversion of flux for wind directions that are contrary to the turbine axis. Finally the numerical simulations have been validated through the wind tunnel tests. The results show that for low air velocity 5–6 m/s, there is a perfect correspondence between the numerical and experimental values and the relative percentage difference between the two methods is less than 1%. • A mini-Ducted Wind Turbine has been analysed by means of numerical simulations. • Optimal configuration to improve performance and reduce size of the analysed system. • Design of a mini- Ducted Wind Turbine that could be integrated in the urban context. • It is possible to exploit up to 432% more energy than a traditional system. • Numerical results correspond to the experimental ones for air velocity of 5–6 m/s. [ABSTRACT FROM AUTHOR]

Dust storms, resulting from aeolian erosion, pose significant environmental hazards, while farmland is one of the main sources of dust storm release. An effective strategy to mitigate surface wind speed and curb dust emissions involves the establishment of windbreaks on the periphery of oasis farmland. This study conducts a series of numerical simulations using computational fluid dynamics (CFD) to explore the airflow fields around windbreaks with diverse systematic structural parameters, encompassing porosity, planting spacing, and fence effects. The main findings are as follows: (1) When the vegetation porosity is consistent (e.g., porosity α = 0.7, 0.8, and 0.9), exact geometry results can effectively reflect the distribution of wall shear stress, while the porous medium model overlooks these details. (2) The "Venturi effect" contributes to the acceleration of surface erosion and improper planting spacing results in an elevation of near-surface velocity. Planting spacing of 0.5 m demonstrates superior wind speed reduction performance, mitigating aeolian erosion and accumulation. (3) When the fence is positioned at l = 5 h (h represents the height of the windbreaks), the flow field around the windbreaks is minimally influenced. The optimal placement distance for fences should be close to the windbreaks, featuring minimal porosity (l = 0 h , α = 0.1), extending the shelter distance from 3 to 4 h to 5–6 h. The research results can provide a theoretical basis for optimizing the plant configuration of biological desertification control and soil erosion control measures. • The exact geometric model of windbreak reflects more details of the three-dimensional flow field. • There is an optimal value between the planting spacing of the windbreak and the venturi effect. • The planting spacing of 0.5 m has better wind speed reduction performance. • The optimal arrangement of the fence should be tightly close to the windbreaks. [ABSTRACT FROM AUTHOR]

Recently, there has been a growing interest in utilizing computational fluid dynamics (CFD) for wind resistant design of tall buildings. A key factor that influences the accuracy and computational expense of CFD simulations is the size of the computational domain. In this paper, the effect of the computational domain on CFD predictions of wind loads on tall buildings is investigated with a series of sensitivity studies. Four distinct sources of domain error are identified which include wind-blocking effects caused by short upstream length, flow recirculation due to insufficient downstream length, global venturi effects due to large blockage ratios, and local venturi effects caused by insufficient clearance between the building and top and lateral domain boundaries. Domains based on computational wind engineering guidelines are found to be overly conservative when applied to tall buildings, resulting in uneconomic grids with a large cell count. A framework for optimizing the computational domain is proposed which is based on monitoring sensitivity of key output metrics to variations in domain dimensions. The findings of this paper help inform modellers of potential issues when optimizing the computational domain size for tall building simulations.

The mass throughput and thus the productivity of a blown film line strongly depends on heat transfer from the film. Existing cooling systems are therefore constantly being further developed. Usually, the film is convectively cooled by cooling rings, coupled with an internal bubble cooling (IBC) system to increase the surface area and the cooling rate. Convection has a major disadvantage which is a low cooling efficiency due to a low heat transfer coefficient. Against this background a flexible air guiding system was developed at the Institute for Plastics Processing (IKV), Aachen, Germany. This system encloses the bubble expansion zone and creates a flow gap between an air guiding flexible membrane and the film bubble. In this gap the cooling air velocity is increased, which leads to a higher cooling efficiency. The novel system can be adjusted to many bubble geometries during the extrusion process and increases the mass throughput by up to 62%. However, higher cooling air velocities lead to film movement in the bubble expansion zone and thus also to considerable film thickness variations. In this article the air guiding system influence on the thickness variations is investigated by quantifying the film movement versus the process parameters. For this purpose, a digital image processing system is used which corelates the film movement phenomena with the film thickness variations. [ABSTRACT FROM AUTHOR]

Drag reduction by injecting air is a promising engineering method for improving ship performance. A novel automatic air intake drag reduction strut structure based on the Venturi effect is proposed for the high-speed small water-plane area twin hull vessels in the present study. The drag reduction strut can achieve the function of automatic air intake when the vehicle is moving at high speed, and the air inhaled and the incoming flow form bubbly flows to cover the strut surface, effectively reducing the drag of the strut. Considering the longitudinal symmetry of the strut structure, a two-dimensional single-chip drag reduction strut structure is designed to facilitate analysis and a solution. The volume of fluid model is combined with the k-ω SST turbulence model, and a numerical simulation is carried out to investigate the variation of the air inflow, the air volume fraction in the bubbly flows of the strut and the drag reduction rate of the strut for different sailing speeds. The analysis result shows that when the proposed model reaches a certain speed, the external air is inhaled by the strut intake duct, and the bubbly flows are formed with the incoming flow covering the surface of the strut, thereby reducing the drag coefficient. Meanwhile, it is found that as the sailing speed increases, the drag reduction rate of the strut gradually rises and its maximum value reaches about 30%. For high sailing speeds, the drag reduction rate is affected by wave-making resistance so that it gradually declines.

This article focuses on evaluating the performance of a relatively new system of a ducted wind turbine with an omnidirectional capture system, the INVELOX system. In the present study, the improvement of such patented system has been developed by performing a detailed numerical analysis varying several geometrical parameters and analysing the effect of changing wind velocity and wind direction. At first, the model validation was performed and the performance of the original system against the wind direction changes was analysed observing that the highest speed ratios are obtained for two specific directions. Based on the previous results, the most critical features of the system have been identified, and then it has been approached a geometric improvement of the system aiming at increasing the system productivity. The results show there is a possibility to largely improve the overall design and extract more energy from the wind respect with the original design. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering for Thermal Energy & Power / Reneng Dongli Gongcheng is the property of Journal of Engineering for Thermal Energy & Power and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Suction devices are integral to the safe delivery of anaesthesia and critical care. They are involved in clearing and aspirating body fluids, blood and debris, as well as employed in scavenging waste gases and diathermy fumes, intraoperative cell salvage systems, and tertiary devices such as vacuum mattresses and specialized wound dressings. All suction devices require three essential components, namely a source of vacuum, a reservoir/collection vessel and suction tubing. Other components of a suction device include an on/off switch, a vacuum regulator, vacuum gauge, filters, an overflow safety trap, an overfill protection device in the collection vessel, and a catheter. Several different types of catheter are available for use in different clinical situations. Vacuum and flow are the main physical principles underlying suction devices. The source of vacuum may be a fixed centrally piped system or a portable device using electrical, pneumatic or manual power. Pneumatically powered suction devices utilize the Bernoulli principle and Venturi effect. The efficiency of each system depends upon principles of displacement, degree of negative pressure and time taken to reach this, the internal resistance of the suction apparatus and the viscosity of the material to be aspirated. [ABSTRACT FROM AUTHOR]

This study analyzed the thermal wind environment at the pedestrian level around urban geometry featuring high-rise buildings using building-resolved large-eddy simulation (LES) while incorporating seasonal atmospheric data. The synthetic inflow generation method and immersed boundary method with wall-function were applied for urban thermal flow LES. The solver was validated using wind tunnel experiments based on the metrics, namely RMSE, FAC2, and hit rates q. The study conducted LESs of thermal wind environments around the Yonsei University campus, featuring two high-rise buildings. The LES results showed that downdraft wind and large-circulation (known to be idealized high-rise building-induced) also occurred around realistic high-rise buildings in urban areas. These induced flows enhanced building wind via the Venturi effect and lowered temperatures at the pedestrian-level by drawing cool air downwards. Additionally, by comparing conditionally averaged quantities on the campus with and without high-rise buildings, we quantified the extent of the building's impact on the urban thermal environment at the pedestrian-level. • We performed LESs of thermal and wind fields on idealized and realistic urban. • Validation studies were performed for tall buildings and idealized urban models. • Tall buildings in urban induced strong downward wind on windward faces. • Induced wind brings down cooler air to pedestrian level, irrespective of season. [ABSTRACT FROM AUTHOR]

Natural ventilation is a way to reduce the energy consumption of building operations and improve the indoor living environment comfort. The venturi cap is designed with a roof, grille and wind deflector to intensify the natural ventilation of buildings. The structural parameters of the venturi cap were designed using an orthogonal design. Fluid analysis software was used for numerical simulation, and variance analysis was used to study the importance of seven influence factors: the width of the roof opening, the roof slope, the height of the wind deflector, the horizontal width of the wind deflector, the angle of the wind deflector, the angle of the grille, and the spacing of the grille slices. The results show that the most significant influencing factor is the width of the roof opening, while significant influence factors include the angle of the grille and the horizontal width of the wind deflector. Additionally, the optimum parameter combination for ventilation performance at the research level was put forward, with the proposed combination achieving a volume flow rate of 5.507 m3/s. The average temperature of the horizontal plane at a height of 1.2 m above the ground was 3.002 K lower than that without a venturi cap, which provides a reference for the optimization of indoor ventilation design in buildings in the Xichang area.

This paper presents the analysis of installing the vertical axis wind turbines between the building passages on an island in Stockholm, Sweden. Based on the idea of wind speed amplification due to the venture effect in passages, practical measurements were carried out to study the wind profile for a range of passage widths in parallel building passages. Highest increment in wind speed was observed in building passages located on the periphery of sland as wind enters from free field. Wind mapping was performed in the island to choose the most favourable location to install the vertical axis wind turbines (VAWT). Using the annual wind speed data for location and measured amplification factor, energy potential of the street was calculated. This analysis verified that small vertical axis wind turbines can be installed in the passage centre line provided that enough space is provided for traffic and passengers.

A series of wind-tunnel tests were carried out to investigate the characteristics of pedestrian-level wind around square buildings with various dimensions, in particular, to examine the effects of building height, building width, building aspect ratio, approaching flow profile and turbulence intensity. It was found that the downwash effect on pedestrian-level wind is significant for a building in boundary layer flow. The maximum speed-up ratio and speed-up area in boundary layer flow (BLF) are much larger than those in a uniform turbulent flow (UTF). The maximum speed-up ratio and speed-up area for a building with constant width in BLF shows an increasing tendency with building height, but this becomes less significant for higher buildings. For a building with constant height in BLF, increase in building width results in smaller aspect ratio, stronger blocking effects, and enhanced downwash effect and Venturi effect. Thus, the speed-up area increases exponentially with building width. For a building with constant aspect ratio in BLF, Venturi effect and downwash effect cause an exponentially increasing speed-up area with building size. • Wind-tunnel tests for pedestrian-level winds around various building models with square plans were carried out. • Height effects, width effects and size effects on pedestrian-level winds are separately investigated. • Two types of downwash effect variations are found and investigated. • Downwash effect and Venturi effect are comparable for the maximum speed-up ratio in boundary layer flow. • Downwash effect is very significant in the speed-up area in boundary layer flow. [ABSTRACT FROM AUTHOR]

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Abstract Modeling and simulation studies of drip irrigation systems have been carried out to improve the fertilizer suction rate for the existing water flow rate of 20,000 litres per hour to the agricultural field. Venturi design (33 mm, 40 mm and 50 mm venturi inlet diameters) and water entry/exit modifications (90° inlet/outlet, 45° inlet & 90° outlet and 45° inlet/outlet) have been carried out in the models and the incompressible fluid flow is simulated in OpenFOAM 5.0 using the simpleFoam solver and realizable K-epsilon (k-ε) turbulence model. Mesh refinement level of (4, 5) was used which is considered as medium grid size. The results are validated using real time experimental setup in the agricultural field. In all the selected conditions, the throat velocity increases linearly with increase in pressure drop and with some variations in the flow distribution. The simulated results obtained for various design conditions using OpenFOAM software satisfies the real time experimental outputs and the 45° entry/exit angle coupled with 33 mm inlet diameter venturi yields the maximum suction rate at the lowest pressure difference. Highlights • Studies on fluid entry and exit angle to venturi are attempted using OpenFOAM software and validated in agricultural field. • Design modification of venturi injector has been carried out to study its effect on fertilizer suction rate. • Different turbulence models (Standard k-ε and realizable k-ε) are applied to the flows to analyze their performance level. [ABSTRACT FROM AUTHOR]

Abstract Invelox is a patented structure designed to capture the incident wind from every direction, guide the collected wind to the ground level and increase its velocity. Previous numerical studies have revealed that a considerable portion of the collected wind escapes the structure from the opposite side of the wind entering Invelox. In the present study, three possible curtain designs are proposed to reduce or fully-eliminate this escaping air. The improved capability of Invelox to augment the wind velocity using these curtain systems is evaluated via numerical simulations. The results show that the best configuration can fully eliminate the escaping air and it will not disturb the air flow uniformity inside the Venturi section. On average, the best design can lead to a 25% increase in the average wind velocity inside the Venturi for the wind velocities of 3–12 m/s. The results also show that although it has been claimed that Invelox accepts wind from all directions, it can only be efficient at the incident wind directions of −90 to 90°. Increasing the turbulent intensity of the upcoming wind from 0 to 20%, however, has no considerable effects on the Invelox speed ratio. Highlights • Three curtain designs are proposed to improve the speed ratio of Invelox. • The proposed modifications are studied numerically. • The best modification eliminated all the escaping air from Invelox. • On average, a 25% increase in the wind velocity inside the Venturi section is achieved. • Invelox works efficiently for the incident wind direction of −90 to 90°. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Venturi negative-pressure secondary dedust device was developed by tests. • The pressure and velocity of Venturi device was revealed by numerical simulation. • The local spray closure technique for dust suppression was proposed. • The dedust effect of local spray closure technique was verified by field test. Abstract In order to enhance the spray for dust suppression performance in a fully-mechanized mining face, based on orthogonal test, comparison test, numerical simulation and field application, the Venturi negative-pressure secondary dedust device was developed. Meanwhile, the local spray closure technique was proposed, which can not only effectively prevent the escape of coal dust from entering the footway space, but also remove coal dust around the respiratory zone from the footway space successfully. The results demonstrated that, under spray pressure of 6 MPa, the Sauter mean droplet size, negative pressure suction flow rate and effective spray distance of the novel dedust device with a throat-to-nozzle distance and throat diameter of 20 mm and 65 mm were 47.37 µm, 11.21 m3/min and 5.4 m respectively. Moreover, the novel dedust device produced droplets to a smaller scale than a single-nozzle. Additionally, the negative pressure and airflow velocity in the negative pressure suction inlet of novel dedust device were within the range from −0.97 Pa to −541.04 Pa and from 2.96 m/s to 27.29 m/s respectively. Finally, compared with the original dust suppression measures, the local spray closure technique can enhance the removal ratio of respiratory dust by an average of 44.3%. [ABSTRACT FROM AUTHOR]