Wind flow on and around U-shaped buildings

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Tugba Inan Gunaydin
Keyword(s):  
Wind Velocity ◽  
Negative Pressure ◽  
Incidence Angle ◽  
Wind Pressure ◽  
Positive Pressure ◽  
Content Type ◽  
Pressure Coefficients ◽  
Building Shape ◽  
Reentrant Corner ◽  
Pressure Distributions

Purpose This paper presents the numerical examination of wind pressure distributions on U-plan shaped buildings having four different depth ratios (DR) as 0.5, 1, 2 and 4 over wind incidence angle (WIA) of 0°. The purpose of this study is to investigate the effect of irregular building form, DRs, distances from the reentrant corner, wind velocity values on and around wind pressure distributions of the buildings. With this aim, ANSYS Fluent 20.0 Computational Fluid Dynamics (CFD) program is used for the analysis. Design/methodology/approach Four U-shaped buildings having the same height, width and wing length but having different DR in plan were analyzed by the application of CFD package of ANSYS 20. With this purpose, wind pressure distributions on and around U-plan shaped buildings were analyzed for the wind velocity values of 2 and 5 m/s over WIA of 0°. Comprehensive results were obtained from the analyses. Findings While the change in the DR values did not create a significant change in positive pressure coefficients on A and E surfaces, negative pressure values increased as the DR decreased. The negative pressure coefficients observed on the A and E surfaces become higher than the positive pressure coefficients with the decrease in the DR. On contrary to that condition, with the decrease in the DR, G surfaces take higher positive pressure coefficients than the negative pressure coefficients. The reason for this is that the DR decreases and negative pressure values on G surface significantly decrease. The effect of the DR on the pressure coefficients is remarkable on B and D surfaces. The negative pressure coefficients on the B and D surfaces tend to increase as the DR decreases. Research limitations/implications This study focused on DRs and wind velocity values effect on pressure coefficients to limit variables. Different building wing dimensions did not take into account. Originality/value Although there are a number of studies related to wind behavior of irregular plan shaped buildings, irregular building forms have not been extensively investigated parametrically, especially in terms of the effect of DR on wind pressures. This study is therefore designed to fill this gap by analyzing impacts of various parameters like building shape with various DRs, WIA and wind velocity values on wind pressure distributions and velocity distributions on and around the building.

Experimental inappropriate ADH secretion caused by positive-pressure respirators

1972 ◽  
Vol 36 (5) ◽  
pp. 608-613 ◽  
Author(s):  
William A. White ◽  
Richard M. Bergland
Keyword(s):  
Antidiuretic Hormone ◽  
Negative Pressure ◽  
Laboratory Model ◽  
Positive Pressure ◽  
Content Type ◽  
Fine Print

✓ A laboratory model was developed for studying antidiuretic hormone (ADH) secretion during mechanical respiratory assist of paralyzed rats. Inappropriate ADH secretion occurred during the use of positive-pressure respirators but did not occur when negative-pressure respirators were used.

scholarly journals Thermal performance of a non–segmented and segmented tall atrium in hot and humid climate

2021 ◽  
Vol 2042 (1) ◽  
pp. 012162
Author(s):  
Priya Pawar ◽  
Deying Zhang ◽  
Xiaoying Wu ◽  
Werner Lang
Keyword(s):  
Wind Velocity ◽  
Air Temperature ◽  
Indoor Air ◽  
Thermal Conditions ◽  
Wind Pressure ◽  
Humid Climate ◽  
Pressure Coefficients ◽  
Starting Point ◽  
Buoyancy Forces ◽  
Hot And Humid Climate

Abstract The study was designed to quantify the thermal conditions in tall atria in office buildings to serve as a starting point towards understanding their performance. The simulation study of a non-segmented and segmented atrium of 250 m height reveals indoor air temperature, wind velocity contours and wind pressure coefficients at various heights of each atrium type. In a hot and humid climate like that of Singapore, the internal temperatures within each atrium stack remain constant at 27°C. However, the wind velocity in the non-segmented atrium (of 0.5 - 0.7 m/s) is lower than acceptable (0.9 m/s) for human occupancy. Adding segments and a larger inlet to the atrium solves the problem of low wind velocity without increasing the effective ambient temperature within the atrium stack. Additionally, the segmented atrium offers the advantage of displaying lower buoyancy forces by lowering the pressure differential within a tall stack thereby providing better comfort conditions.

Numerical Simulation of Mean Wind Pressure on the Roof of Yantai Gymnasium

2012 ◽  
Vol 226-228 ◽  
pp. 1260-1264
Author(s):  
Xi Meng ◽  
Ri Gao ◽  
Hai Jun Zhang
Keyword(s):  
Numerical Simulation ◽  
Wind Tunnel ◽  
Pressure Distribution ◽  
Negative Pressure ◽  
Small Area ◽  
Wind Tunnel Test ◽  
Wind Pressure ◽  
Windward Side ◽  
Positive Pressure ◽  
Distribution Law

In order to determine the distribution of wind load on the roof, wind tunnel test and numerical simulation are both carried out. Then the distribution of mean wind pressure under different wind directions is obtained and the features of mean wind pressure are also analyzed. The datas show that wind pressure distribution of the roof is predominantly negative pressure; only a small area of windward side is positive pressure distribution. The peak of negative pressure appears at the roof ridge or windward long eaves, and varies as changes of wind direction. Meanwhile, the comparison between the results of the numerical simulation and wind tunnel test shows that the distribution law of both is almost the same, but in some areas that flow separation is serious, the error is larger. Then the reasons for the error are discussed.

Comparative Study between Field Measurement and Wind Tunnel Test of Wind Pressure on Wuhan International Stock Building

2014 ◽  
Vol 590 ◽  
pp. 341-348
Author(s):  
Shu Guo Liang ◽  
Xiao Hui Peng ◽  
Lei Wang
Keyword(s):  
Wind Tunnel ◽  
Comparative Study ◽  
Field Measurement ◽  
Wind Tunnel Test ◽  
Wind Pressure ◽  
Pressure Coefficients ◽  
Pressure Distributions ◽  
The Mean

Field measurement and wind tunnel test of wind pressure on the surfaces of Wuhan International Stock Building were carried out in this paper, and the mean wind pressure coefficients, RMS wind pressure coefficients, wind pressure spectra as well as coherence functions were discussed. Meanwhile wind pressure distributions were analyzed. The results demonstrated that the distribution of the surface mean wind pressure coefficients obtained by wind tunnel test approximately agreed with that by field measurement, especially the mean wind pressure coefficients on the windward obtained by the wind tunnel test fitted those obtained by the field measurement well, while the RMS wind pressure coefficients of the wind tunnel results are smaller than those of field measurement, and the RMS wind pressure coefficients of some measure points of field measurement fluctuated greatly.

scholarly journals Probability Characteristics, Area Reduction, and Wind Directionality Effects of Extreme Pressure Coefficients of High-Rise Buildings

2021 ◽  
Vol 11 (15) ◽  
pp. 7121
Author(s):  
Shouke Li ◽  
Feipeng Xiao ◽  
Yunfeng Zou ◽  
Shouying Li ◽  
Shucheng Yang ◽  
...  
Keyword(s):  
Probability Distribution ◽  
Pressure Coefficient ◽  
Wind Pressure ◽  
Extreme Pressure ◽  
Distribution Law ◽  
Distribution Fitting ◽  
Pressure Coefficients ◽  
High Rise ◽  
Area Reduction ◽  
The Mean

Wind tunnel tests are carried out for the Commonwealth Advisory Aeronautical Research Council (CAARC) high-rise building with a scale of 1:400 in exposure categories D. The distribution law of extreme pressure coefficients under different conditions is studied. Probability distribution fitting is performed on the measured area-averaged extreme pressure coefficients. The general extreme value (GEV) distribution is preferred for probability distribution fitting of extreme pressure coefficients. From the comparison between the area-averaged coefficients and the value from GB50009-2012, it is indicated that the wind load coefficients from GB50009-2012 may be non-conservative for the CAARC building. The area reduction effect on the extreme wind pressure is smaller than that on the mean wind pressure from the code. The recommended formula of the area reduction factor for the extreme pressure coefficient is proposed in this study. It is found that the mean and the coefficient of variation (COV) for the directionality factors are 0.85 and 0.04, respectively, when the orientation of the building is given. If the uniform distribution is given for the building’s orientation, the mean value of the directionality factors is 0.88, which is close to the directionality factor of 0.90 given in the Chinese specifications.

Effects of different wind directions on ventilation of surrounding areas of two generic building configurations in Hong Kong

2021 ◽  
pp. 1420326X2110160
Author(s):  
Kai Yip Lee ◽  
Cheuk Ming Mak
Keyword(s):  
Wind Velocity ◽  
Natural Ventilation ◽  
Urban Environments ◽  
Air Pressure ◽  
Pressure Distributions ◽  
Air Intake ◽  
Dynamics Simulations ◽  
Surrounding Areas ◽  
Effective Use ◽  
Velocity Zone

This study investigated effects of incident wind angles on wind velocity distributions in wakes of two generic building configurations, namely, ‘T’- and ‘+’-shaped, and the air pressure distributions along their leeward walls by using computational fluid dynamics simulations. Results show that when the wind approaches laterally (90°) (vs. when the wind is direct (0°)), the downwind length and maximum bilateral width of the low-wind velocity zone in the wake of ‘T’-shaped building decrease by 11.5% and 37.9%, respectively. When the incident wind is oblique (45°) (vs. when it is direct), the length and width of this low-wind velocity zone in the wake of ‘+’-shaped building decrease by 15.0% and 30.9%, respectively. Furthermore, results show that the air pressure on the leeward walls of the ‘T’- and ‘+’-shaped buildings gradually decreases along with the building height. The resulting low-wind conditions on upper floors of buildings reduce the fresh air intake of their leeward units utilizing natural ventilation. It is particularly apparent in the case of direct approaching wind. Thus, the appropriate selection of building configurations and their orientations allows for the most effective use of wind to enhance ventilation in indoor and urban environments.

Numerical Calculation of the Pressure Distributions on a Rudder Surface

2012 ◽  
Vol 562-564 ◽  
pp. 1172-1176
Author(s):  
Jing Ping Wu ◽  
Shun Huai Chen ◽  
Ji Cheng Xiao
Keyword(s):  
Numerical Calculation ◽  
Density Distribution ◽  
Viscous Flow ◽  
Potential Theory ◽  
Airfoil Surface ◽  
Pressure Coefficients ◽  
Viscosity Effect ◽  
Pressure Distributions ◽  
Structure Strength ◽  
Grid Nodes

This paper numerically calculates the pressure distributions of a rudder of a ship for structure strength design. The sections profile of the rudder is NACA0020 airfoil. The viscous flow is simulated by FLUENT commercial software, while the model and mesh is generated by GAMBIT software. A 2D viscous flow around a NACA0020 airfoil is calculated firstly. Some notices are given here about the magnitude of computing domain, the density distribution and the numbers of grid nodes on the airfoil surface in order to gain better results. Then, based on these experiences, the viscous flow around a 3D rudder is simulated. The calculated pressure coefficients on the rudder’s section are compared with the experiment results and BEM results of the potential theory. At the attack angles and , the three results agree well with each other. However, when the attack angle is , the viscous results from FLUENT give better agreement with the experiment results than the BEM results. This conclusion confirms that the viscosity effect is great in the case of large attack angles.

Study of Toynbee Phenomenon by Combined Intranasopharyngeal and Tympanometric Measurements

1988 ◽  
Vol 97 (2) ◽  
pp. 199-206 ◽  
Author(s):  
Yehuda Finkelstein ◽  
Yuval Zohar ◽  
Yoav P. Talmi ◽  
Nelu Laurian
Keyword(s):  
Middle Ear ◽  
Negative Pressure ◽  
Pressure Change ◽  
Positive Pressure ◽  
New Information ◽  
Pressure Changes ◽  
Rapid Pressure

The Toynbee maneuver, swallowing when the nose is obstructed, leads in most cases to pressure changes in one or both middle ears, resulting in a sensation of fullness. Since first described, many varying and contradictory comments have been reported in the literature concerning the type and amount of pressure changes both in the nasopharynx and in the middle ear. In our study, the pressure changes were determined by catheters placed into the nasopharynx and repeated tympanometric measurements. New information concerning the rapid pressure variations in the nasopharynx and middle ear during deglutition with an obstructed nose was obtained. Typical individual nasopharyngeal pressure change patterns were recorded, ranging from a maximal positive pressure of + 450 to a negative pressure as low as −320 mm H2O.

Effect of airway wall flexibility on clearance by simulated cough

1987 ◽  
Vol 63 (2) ◽  
pp. 707-712 ◽  
Author(s):  
V. Soland ◽  
G. Brock ◽  
M. King
Keyword(s):  
Negative Pressure ◽  
Rectangular Cross Section ◽  
Dynamic Compression ◽  
Wave Formation ◽  
Bottom Surface ◽  
Positive Pressure ◽  
Airway Wall ◽  
Wall Flexibility ◽  
Mucus Rheology ◽  
The Relationship

In our previous study, we investigated the relationship between mucus rheology, depth of mucus layer, and clearance by simulated cough. The purpose of the present study was to examine the effect of airway wall flexibility on the clearance of mucuslike gels. Transient airflows similar to cough were generated by both positive and negative pressure, the latter to mimic the dynamic compression that occurs during real cough. As in the previous study, the trachea was modeled as a trough of rectangular cross section with only the bottom lined with the mucus simulant. Clearance was followed by observing the displacement of marker particles. Since cough clearance is intimately related to wave formation in the mucus blanket, we hypothesized that clearance might be impeded if the wave formation occurred simultaneously in the wall and its lining layer. Thus, in one set of experiments the bottom rigid surface of the model trachea was replaced with a frame over which a flexible membrane could be drawn, whereas in the other set the rigid top was replaced by the frame. We also examined the effect of negative-pressure cough in excised canine tracheae, comparing the case where the tracheal membrane was free to deform vs. the case where it was secured. For the rigid-walled model, clearance by positive or negative pressure, with matched flow pattern, was the same. With the mucus simulant lining the flexible bottom surface, clearance increased with increasing membrane flexibility for negative-pressure cough and decreased for positive-pressure cough.(ABSTRACT TRUNCATED AT 250 WORDS)

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