scholarly journals Computational assessment of wind flow field on and around atypical buildings

2020 ◽  
Author(s):  
Rajasekarababu KB
Keyword(s):  
Surface Pressure ◽  
Pressure Coefficient ◽  
Tall Buildings ◽  
Ground Level ◽  
Pressure Variation ◽  
Middle Level ◽  
Computational Results ◽  
Pressure Coefficients ◽  
Building Surfaces ◽  
Side Face

Abstract This article provides an overview of pressure coefficients ( Cp ) on atypical tall buildings with the application of CFD. Various modifications in architectural shapes on tall buildings eventually lead to a reduction in the wind load on building surfaces. The surface pressure on conventional (Square and rectangular) buildings is relatively different in comparison to other tall buildings. This study is to evaluate the surface pressure coefficient over rectangular, taper and setback buildings. The computational results show that the taper building has 7% Cp rise at ground level ( y/H= 0.225) in the windward face, and 34% Cp fall at the middle level ( y/H= 0.475) in the side face when compared with the rectangular building. Whereas for the setback building, Cp at ground level near setback ( y/H= 0.225) has reduced to about 25% and about 6% at the middle level ( y/H= 0.475) in windward than that in the rectangle building. Also, the side faces of the setback showed a 15% drop in Cp than other buildings. In leeward face, Cp is reduced to 56% near setback at the top of the building ( y/H= 0.725). This valuation of the Cp on these buildings shows that the effect of setbacks on building reduces the pressure variation on all faces and the downstream wake vortices.

scholarly journals Prognosis of Wind-tempted Mean Pressure Coefficients of Cross-shaped Tall Buildings Using Artificial Neural Network

2020 ◽  
Author(s):  
Rajdip Paul ◽  
Sujit Kumar Dalui
Keyword(s):  
Mean Squared Error ◽  
Pressure Coefficient ◽  
Tall Buildings ◽  
Parametric Models ◽  
Wind Pressure ◽  
Pressure Coefficients ◽  
Building Models ◽  
Wide Range ◽  
Close Relationship ◽  
Artificial Neural

The present paper focuses on the study of wind-induced responses of cross-plan shaped tall buildings. Initially, three parametric building models are studied for the purpose with a constant plan area 22500 mm2. The length and velocity scales are taken as 1:300 and 1:5, respectively. Wind angle of attack (WAA) is considered from 0° to 330° with an increment of 30°. At first, the external surface pressure coefficients (Cp) at different faces of the models are carried out for different wind occurrence angles employing Computational Fluid Dynamics method of simulated wind flow. Again, Fast Fourier Transform (FFT) fitted expressions as the sine and cosine function of WAA are proposed for attaining mean wind pressure coefficient on the building faces. The accuracy of the Fourier series expansions is justified by presenting histograms of sum square error (SSE), R2 value and root mean square error (RMSE). The results are also compared by training Artificial Neural Networks (ANN). Training is continued till Regression (R) values are more than 0.99 and Mean Squared Error (MSE) tends to 0, ensuring a close relationship among the outputs and targets. The face-wise value of (Cp) obtained using all three methods, are plotted. The error histograms of the ANN models show that the fitting data errors are spread within a reasonably good range. It is observed that the deviation in the result is not more than 5% in any case. Finally, the ANN predictions are presented for nine parametric models to cover a wide range of possible cross-shaped buildings.

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.

CFD Modeling of Pressure Coefficients for a Natural Ventilation Study in an Experimental Low Rise Building

2013 ◽  
Author(s):  
Robel Kiflemariam ◽  
Cheng-Xian Lin
Keyword(s):  
Natural Ventilation ◽  
Pressure Coefficient ◽  
Wind Pressure ◽  
Analytical Models ◽  
Cfd Modeling ◽  
Engineering Practice ◽  
Pressure Coefficients ◽  
Wind Pressure Coefficient ◽  
Detailed Assessment ◽  
Ventilation Rates

Mean wind pressure coefficient (Cp) is one of the major input data for natural ventilation study using building energy simulation approach. Due to their importance, they need to be accurately determined. In current engineering practice, tables and analytical Cp models only give mostly averaged results for simpler models and configurations. Considering the limitation of tables and analytical models, Computational Fluid Dynamics (CFD) could provide a means for an accurate and detailed assessment of Cp. In this paper, we make use of a relatively high resolution, detailed experiments done at Florida Intentional University to validate a CFD modeling of the pressure coefficients Cp. The results show that existing CFD model has a good agreement with experimental results and gives important information of distribution of Cp values over the surface. The local values of the Cp are investigated. In addition, the CFD derived Cp and discharge coefficient (Cd) values are utilized in semi-analytical ventilation models in order to get a more accurate value of ventilation rates.

Some Characteristics of High Waves in Closed Channels Approaching Kelvin-Helmholtz Instability

1977 ◽  
Vol 99 (2) ◽  
pp. 339-346 ◽  
Author(s):  
E. Kordyban
Keyword(s):  
Surface Pressure ◽  
Water Waves ◽  
Internal Flow ◽  
Flow Patterns ◽  
Pressure Variation ◽  
Helmholtz Instability ◽  
Wave Celerity ◽  
Theoretical Considerations ◽  
Wave Shapes

The characteristics of water waves produced by flowing air in closed channels were studied to uncover the effects of surface pressure variation. From theoretical considerations, it is proposed that the point of onset of the Kelvin-Helmholtz instability for such waves may be found from 1.35ρaρwVc2ghc=1 Photographs of internal flow patterns and wave shapes confirm the occurrence of this instability, but the theoretically predicted reduction in wave celerity does not occur. The wave celerity for high waves was found to be predictable by the formula C=0.191gLtanh2πhwL1/2 The measured height to length ratios for the highest observed waves are of the order of 0.1.

scholarly journals Acid Rain Phenomenon in Niger Delta Region of Nigeria: Economic, Biodiversity, and Public Health Concern

2008 ◽  
Vol 8 ◽  
pp. 811-818 ◽  
Author(s):  
J. K. C. Nduka ◽  
O. E. Orisakwe ◽  
L. O. Ezenweke ◽  
T. E. Ezenwa ◽  
M. N. Chendo ◽  
...  
Keyword(s):  
Acid Rain ◽  
Niger Delta ◽  
Tall Buildings ◽  
Ground Level ◽  
Anthropogenic Sources ◽  
Health Concern ◽  
Delta Region ◽  
Niger Delta Region ◽  
Port Harcourt ◽  
June July

Rain samples were collected from Warri and Port Harcourt, two major oil-producing cities of Nigeria in April-June, July-August, and September-October 2005 and 2006. Awka, a “non-oil” city was used as control. Samples were collected from three points, using clean plastic basins fastened to a table, 2 m above ground level and 115 m away from tall buildings and trees. Water samples were filtered and acidity determined using digital pHmeter. The results show that the rain samples were acidic. The pH values for the 2 years under study show that the rainfall in Warri was more acidic than that of Port Harcourt. Oil exploration and other anthropogenic sources may be responsible for the acid rain in the Niger Delta region of Nigeria.

Investigation of Supercritical Flow and Shape of Flip Bucket Spillways on Coefficients of Dynamic Pressure

2020 ◽  
Vol 143 (6) ◽  
Author(s):  
Hessam Vatandoust ◽  
Hamidreza Yarmohammadi ◽  
Mohammadreza Kavianpour
Keyword(s):  
Froude Number ◽  
Pressure Fluctuation ◽  
Dynamic Pressure ◽  
Pressure Coefficient ◽  
Pressure Fluctuations ◽  
Experimental Studies ◽  
Flow Speed ◽  
Middle Part ◽  
Statistical Characteristics ◽  
Pressure Coefficients

Abstract Pressure fluctuation is one of the major turbulent flow characteristics. It may cause crucial problems for hydraulic structures. This research is based on experimental studies, and it focuses on the measurements of pressure fluctuations along flip bucket spillways with different geometrical characteristics. The function of the flip bucket spillway is discharging floods from reservoir dams which are energy storage source measurements of dynamic pressures on three different models of flip buckets that were performed for this investigation. Pressure fluctuation of the flip buckets have been measured within a range of Froude numbers from 5 to 13 (Fr = u/gy, where u is the flow speed, y is the depth, and g is 9.81 m/s2). Statistical characteristics of pressure fluctuations, the location, and the values of maximum and minimum fluctuations have also supplemented the study. The results show that the coefficients of pressure fluctuations (Cp = RMS/(0.5(u2/g)) where RMS is the root-mean-square of pressure fluctuation, u is the flow speed, and g is 9.81 m/s2) reduce as the Froude number (Fr) of flow increases, except a maximum Froude number. Pressure coefficients increase along the flip bucket with incremental mutations in the transformation area of the flip bucket. In the middle part of the flip bucket spillway, pressure coefficient values decrease. Additionally, as B/r (B is the width of the flip bucket and r is the radius of the flip bucket) ratio increases, pressure coefficients become larger and this process continues along the flip bucket.

Chip-on-Beam and Hydrostatic Calibration of the Piezoresistive Coefficients on (111) Silicon

2007 ◽  
Author(s):  
Chun-Hyung Cho ◽  
Richard C. Jaeger ◽  
Jeffrey C. Suhling ◽  
M. Kaysar Rahim
Keyword(s):  
Pressure Coefficient ◽  
Experimental Methods ◽  
Temperature Dependent ◽  
Pressure Coefficients ◽  
Stress Sensors ◽  
Wide Range ◽  
Complete Set ◽  
Stress Sensing ◽  
Test Chips ◽  
P Type

Stress sensing test chips are used to investigate die stresses arising from assembly and packaging operations. The chips incorporate resistor or transistor sensing elements that are able to measure stresses via the observation of the changes in their resistivity/mobility. The piezoresistive behavior of such sensors is characterized by three piezoresistive (pi) coefficients, which are electro-mechanical material constants. Stress sensors fabricated on the surface of the (111) silicon wafers offer the advantage of being able to measure the complete stress state compared to such sensors fabricated on the (100) silicon. However, complete calibration of the three independent piezoresistive coefficients is more difficult and one approach utilizes hydrostatic measurement of the silicon “pressure” coefficients. We are interested in stress measurements over a very broad range of temperatures, and this paper present the experimental methods and results for hydrostatic measurements of the pressure coefficient of both n- and p-type silicon over a wide range of temperatures and then uses the results to provide a complete set of temperature dependent piezoresisitive coefficients for the (111) silicon.

Experimental investigation of pressure distribution characteristics of a flying-wing model using PSP

2020 ◽  
Vol 34 (14n16) ◽  
pp. 2040088
Author(s):  
Hongbiao Wang ◽  
Baoshan Zhu ◽  
Jian Xiong
Keyword(s):  
Pressure Distribution ◽  
Surface Pressure ◽  
Pressure Measurement ◽  
Pressure Coefficient ◽  
Leading Edge ◽  
Distribution Characteristics ◽  
Characteristic Analysis ◽  
Camera System ◽  
Wing Model ◽  
The Impact

To investigate the static pressure distribution characteristics of a flying-wing model, an advanced binary pressure sensitive paint (PSP) technique is introduced. It has low-temperature sensitivity and can compensate the errors induced by temperature. The pressure measurement test was performed in 0.6 m trisonic wind tunnel at angles of attack ranging from 0[Formula: see text] to 12[Formula: see text] in supersonic condition, adopting a low-aspect-ratio flying wing model. The binary PSP is sprayed on the upper surface of the model while pressure taps are installed on the upper surface of the right wing. Luminescent images of two probes are acquired with a color charge-coupled-device camera system and processed with calibration results. During the test, the surface pressure is measured by PSP and transducer, respectively. The results obtained show that the binary paint is of advantage to the surface pressure measurement and flow characteristic analysis. The high-resolution pressure spectra at different angle of attack clearly reveal the impact of leading edge vortex on the upper surface pressure distributions. The pressure measured by PSP also agrees well with the pressure tap results. The root mean square error of pressure coefficient is 0.01 at [Formula: see text], [Formula: see text].

Time History Analysis of Steel Tall Buildings

2014 ◽  
Vol 1025-1026 ◽  
pp. 918-921 ◽  
Author(s):  
Yong Chul Kim ◽  
Sung Won Yoon
Keyword(s):  
Wind Direction ◽  
Time History ◽  
Tall Buildings ◽  
Bending Moment ◽  
Ground Level ◽  
Structural Systems ◽  
Loading Conditions ◽  
Normal Stresses ◽  
History Analysis ◽  
Principal Axes

The results of wind tunnel experiments were used to conduct time history analyses of three conventional square cross-section tall buildings with different structural systems. The primary purpose of the study was the direct comparison of the effects of the wind loads on the steel tall buildings. Time history analyses were conducted by applying local wind forces to the center of each floor. The results showed that, although the bending moments in the ground-level column on the two principal axes were different, the peak normal stresses were almost the same regardless of the structural systems. Similar observations were made regarding the tip displacements. Furthermore, analyses for the various loading conditions revealed that the contribution of the bending moment in the across-wind direction was the largest, followed by that in the along-wind direction. The ratio of the peak normal stresses for different loading conditions were observed to be almost the same regardless of the structural systems.

Interference Effects of Wind Flow around Three Parallel-Aligned Wall-Mounted Cubes Placed in Turbulent Boundary Layer

2013 ◽  
Vol 805-806 ◽  
pp. 416-419
Author(s):  
Dan Gu ◽  
Hee Chang Lim
Keyword(s):  
Surface Pressure ◽  
Pressure Coefficient ◽  
Azimuth Angle ◽  
Wind Flow ◽  
Interference Effects ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Pressure Distributions ◽  
Close Proximity ◽  
Flow Interference

The study undertook various calculations of the turbulent wind flow around a body in close proximity to neighboring obstacles, with the aim of gaining an understanding of the wind velocity and the surface-pressure variations with respect to the azimuth angle of wind direction and the gap distance between the obstacles. This paper presents the effects of wind flow interference among three parallel-aligned wall-mounted cubes for azimuth angles of Φ = 0°, 15°, 30°, and 45° and gap distances of G = 0.5h, 1.0h, 1.5h, and ∞ (i.e., a single cube), where G is the gap distance and h is the cube height. A transient detached eddy simulation (DES) was carried out to calculate the highly complicated wind flow domain around the three cubes to observe the surface-pressure, velocity, vortex and spectra characteristics. The results indicate that an increasing wind azimuth angle can even change the mean surface pressure coefficient on the side face of the center cube from negative to positive value. In addition, because of the interference effects, the velocity and pressure distributions around the center cube also show a substantial change depending on the gap distance.

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