Wind Pressure Coefficients Research Articles

Analysis of Wind Speed and Wind Pressure on the Facades in Frequency Domain for the Modelling of Air Change Rate

Air exchange in buildings is driven by pressure difference across the building envelope caused by wind and difference in density between external and internal air. The evaluation of the influence of wind on the air change rate is usually limited to the analysis of the hourly mean wind speed. Wind is a random phenomenon characterized by the broad energy spectrum. The high frequency part can be responsible for the oscillation of the air through the openings resulting in the increased air exchange. Wind pressure coefficient on the leeward site mostly depends on the form characteristics of the object in relation to wind direction. The analysis of wind speed and wind pressure on the facades in frequency domain can deliver interesting data to air change rate model. Some of the results of continuous measurements carried out on a single-family house for 8 months are presented in frequency domain. The statistics of wind speed, wind direction and pressure differences across the 6 building components are calculated. The wind turbulence and the pressure fluctuations on the facades and the roof of the building are being investigated using energy spectra of their signals. Farther analysis of the experimental results is needed to be able to include high frequency wind in the infiltration model.

Study of Wind Loads and Wind Speed Amplifications on High‐Rise Building with Opening by Numerical Simulation and Wind Tunnel Test

High‐rise buildings are very sensitive to wind excitations, and wind‐induced responses have always been the key factors for structural design. Facade openings have often been used as aerodynamic measures for wind‐resistant design of high‐rise buildings to meet the requirement of structural safety and comfort. Obvious wind speed amplifications can also be observed inside the openings. Therefore, implementing wind turbines in the openings is of great importance for the utilization of abundant wind energy resources in high‐rise buildings and the development of green buildings. Based on numerical simulation and wind tunnel testing, the wind loads and wind speed amplifications on high‐rise buildings with openings are investigated in detail. The three‐dimensional numerical simulation for wind effects on high‐rise building with openings was firstly carried out on FLUENT 15.0 platform by SST k − ε model. The mean wind pressure coefficients and the wind flow characteristics were obtained. The wind speed amplifications at the opening were analyzed, and the distribution law of wind speed in the openings is presented. Meanwhile, a series of wind tunnel tests were conducted to assess the mean and fluctuating wind pressure coefficients in high‐rise building models with various opening rates. The variation of wind pressure distribution at typical measuring layers with wind direction was analyzed. Finally, the wind speed amplifications in the openings were studied and verified by the numerical simulation results.

Distribution of the external pressure coefficients on the elliptic tower: experimental measurement compared with numerical modelling

The wind flow around the elliptical object was investigated experimentally in the BLWT wind tunnel in Bratislava and subsequently solved by computer wind flow simulation. On a high-rise building model, the external wind pressure coefficients were evaluated for different wind directions and then compared with the numerical CFD simulation in ANSYS, where different models of turbulence and mesh types were used. The aim of the article was to evaluate and compare the obtained values and after analysing the results to choose the most suitable model of turbulence and mesh types, which showed the smallest deviations from the experimental values.

Influence of the near standing hall for wind flowing around group of circular cylinders

This article deals with experimental investigation of air flow around in – line standing circular cylinders and influence of nearby standing hall on external wind pressure distribution. The wind pressure distribution on the structures is an important parameter in terms of wind load calculation. For vertical circular cylinders in a row arrangement only wind force coefficient is possible find in Eurocode. 1991-1-4. External wind pressure coefficient depends on wind direction and the ratio of distance and diameter b. Influence of nearby standing structure is not possible find in Eurocode. The series of parametric wind tunnel studies was carried out in Boundary Layer Wind Tunnel (BLWT) STU to investigate the external wind pressure coefficient in turbulent wind flow. Experimental measurements were performed in BLWT for 2 reference wind speeds, which fulfilled flow similarity of prototype and model. We have compared the results of free in - line standing 3 circular cylinder and influence of hall on distribution of wind pressure at 3 height levels in turbulent wind flow and these results were compared with values in EN 1991-1-4.

Field monitoring and wind tunnel study of wind effects on roof overhang of a low‐rise building

Roof overhang is one of the most easily damaged parts of low-rise buildings during windstorms. To investigate the wind-induced pressure distributions and forces on the roof overhang of a typical low-rise building, field monitoring during two typhoons and detailed wind tunnel test are conducted in this paper. Correlation analysis is performed to analyze the wind pressures on the upper and lower surfaces of the roof overhang. Moreover, cross-comparisons among the wind tunnel testing results, full-scale measurements, and design provisions are made for validation purposes. The comparative study illustrates that the model-scale experimental results of wind pressure coefficients, lift, and bending moment coefficients on the roof overhang are generally in reasonable agreement with the full-scale measurements, except for the peak negative pressure coefficients and lift coefficients for several wind directions. In addition, it is observed that the suctions on the roof overhang determined from the wind tunnel test and the full-scale measurements are lower than those stipulated in ASCE 7-16. The combined field measurement and model testing study aims to further understand the wind effects on roof overhang during windstorms and improve the wind-resistant design of low-rise buildings in tropic cyclone-prone regions.

Wind Pressure Coefficients and Spectrum Estimation of Dome by Improved Delayed Detached Eddy Simulation

Wind Pressure Coefficients and Spectrum Estimation of Dome by Improved Delayed Detached Eddy Simulation

Low-rise gable roof buildings pressure prediction using deep neural networks

This paper presents a deep neural network (DNN) based approach for predicting mean and peak wind pressure coefficients on the surface of a scale model low-rise, gable roof building. Pressure data were collected on the model at multiple prescribed wind directions and terrain roughness. The resultant pressure coefficients quantified from a subset of these directions and terrains were used to train a DNN to predict coefficients for directions and terrains excluded from the training. The approach can leverage a variety of input conditions to predict pressure coefficients with high accuracy, while the prior work has limited flexibility with the number of input variables and yielded lower prediction accuracy. A two-step nested DNN procedure is introduced to improve the prediction of peak coefficients. The optimal correlation coefficients of return predictions were 0.9993 and 0.9964, for mean and peak coefficient prediction, respectively. The concept of super-resolution based on global prediction is also discussed. With a sufficiently large database, the proposed DNN-based approach can augment existing experimental methods to improve the yield of knowledge while reducing the number of tests required to gain that knowledge.

Numerical and experimental study of the aerodynamic characteristics around two-dimensional terrain with different slope angles

Complicated terrain was considered and simplified as two-dimensional (2D) terrain in a dynamical downscaling model and a parametric wind field model for typhoons developed by the Shanghai Typhoon Institute. The 2D terrain was further modeled as uphill and downhill segments with various slope angles relative to the incoming flow. The wind speed ratios and pressure characteristics around the 2D terrain were numerically and experimentally investigated in this study. Aerodynamic characteristics of the 2D terrain with a limited-length upper surface were first investigated in the wind tunnel with sheared incoming flow. The corresponding numerical investigation was also conducted by using the commercial computational fluid dynamics code FLUENT with the realizable k-e turbulence model. Special efforts were made to maintain the inflow boundary conditions throughout the computational domain. Aerodynamic characteristics were then investigated for the ideal 2D terrain with an unlimited-length upper surface by using a numerical method with uniform incoming flow. Comparisons of the different terrain models and incoming flows from the above studies show that the wind pressure coefficients and the wind speed ratios are both affected by the slope angle. A negative peak value of the wind pressure coefficients exists at the escarpment point, where flow separation occurs, for the uphill and downhill terrain models with slope angles of 40° and 30°, respectively. Correspondingly, the streamwise wind speed ratios at the points above the escarpment point for the uphill terrain model increase with increasing slope angle, reach their peak values at the slope angle of α = 40° and decrease when the slope angle increases further. For the downhill terrain model, similar trends exist at the points above the escarpment point with the exception that the critical slope angle is a = 30°.

Estimating the wind pressure coefficient for single-span greenhouses using an large eddy simulation turbulence model

The wind pressure coefficient (Cp) can be divided into a mean wind pressure coefficient (Cp, mean) and peak wind pressure coefficient (Cp, peak). In this study, the Cp, mean and Cp, peak values of single-span greenhouses were estimated using time-dependently computed large eddy simulation (LES) of the computational fluid dynamics (CFD) model. First, the Cp, mean and Cp, peak values of single-span greenhouses were measured through a wind tunnel test considering various experimental conditions, such as the roof slope and roof curvature radius. The CFD-computed Cp, mean and Cp, peak values were compared with those measured in the wind tunnel for the validation of the CFD model. Especially, the computed Cp, mean values using the LES model were compared with the computed Cp, mean values using the RANS model performed by Kim, Lee, and Kwon (2017). Consequently, the LES model predicted the Cp, mean values more accurately than those predicted by the RANS. In addition, the Cp, peak values computed using the LES model showed only fine differences with those measured in some other regions; however, the overall tendency was similar between the measured and computed Cp, peak values. From these results, it was determined that the LES model can properly predict the Cp, peak values as well as the Cp, mean values.

Evaluation of various national greenhouse design standards for wind loading

The greenhouse design standard for South Korea is under revision to ensure the structural safety of greenhouses in response to strong winds. In order to ensure that suitable design standards for structural safety are adopted, wind load criteria for a range of countries have been analysed. The provisions for wind load, correction factors, and wind pressure coefficients were analysed using greenhouse design standards from Korea, China, Japan, United States of America (USA), and European Union (EU) (CEN, 2001; JGHA, 2016; MAFRA, 1999; MOHURD, 2017; NGMA, 2004). Although the calculations are similar throughout these greenhouse design standards (CEN, 2001; JGHA, 2016; MAFRA, 1999; MOHURD, 2017; NGMA, 2004), different factors are used to calculate wind load. From the analysed data, a structural analysis was conducted to evaluate the structural safety of the designs for wind load. The results indicated that a relatively rigid member should be used for a greenhouse framework constructed using the greenhouse design standard from USA (NGMA, 2004) and that a relatively inexpensive greenhouse could be constructed using the greenhouse design standard from Japan (JGHA, 2016).

Python-based calculation tool of wind-pressure coefficients on building envelopes

Wind pressure distribution is an essential factor for calculation of airflow rates in controlled natural ventilation systems for both indoor air quality and cooling purposes. A pressure coefficient calculation model, CpCalc, with a modular parametric approach based on analysis of wind tunnel tests was developed by Mario Grosso within the COMIS workshop, held at Lawrence Berkeley Laboratory, UCB, CA, USA, in 1988-1992, and upgraded for the European Project PASCOOL in 1994-2001. This software allows for calculating Cp at any point of a building façade and roof slope as a function of various climate, environmental, and building geometry parameters. The present paper describes a further upgrading of this software using a Pyton script, which allows for applying CpCalc to hourly-based energy dynamic simulation codes as well as being connectable in future with parametric design software.

Research on the wind pressure coefficient in natural wind calculations for extra-long highway tunnels with shafts

Natural wind can be applied to the optimal design of extra-long highway tunnel ventilation systems for energy saving. The main objective of this paper is to study the values of the wind pressure coefficient to propose a more reasonable method for calculating natural wind. In this paper, the components of natural wind pressure in an extra-long tunnel are first analyzed, and a more reasonable calculation method for natural wind velocity in an extra-long highway tunnel with multiple shafts is proposed. Then, the values of the wind pressure coefficient under different working conditions are obtained through laboratory tests on a reduced scale model tunnel. Moreover, a field measurement of natural ventilation is carried out to validate the theoretical calculation above, and this method is used to analyze large amounts of meteorological monitoring data to obtain the design natural wind velocity inside the tunnel. The results show that the wind pressure coefficient is a critical parameter impacting the value of the wind wall pressure difference, ranging mainly from 0.6 to 0.85. The theoretical calculation results for the internal wind velocity are in good agreement with the field measurement data in the Liupanshan Tunnel, which validates the feasibility of the proposed calculation method.

Experimental investigation on the effects of inter-layer gaps on wind loads of cantilevered stadium roofs

To meet the ventilation requirement, an engineer needs to design the cantilevered roof of a stadium as a layered one with gaps between the layers. In order to further understand the wind resistance performance of such structures, a wind tunnel test was carried out on a 1:200 scaled stadium model considering two roof inter-layer cases: opened gaps and blocked gaps. The laws of lift force coefficients and net wind pressure coefficients were compared for these two gap conditions. The study results indicate that the roof experiences larger mean lift force on both top and bottom surfaces when the inter-layer gaps are blocked. However, the roof gaps can reduce the fluctuating lift force on top roof surface and the net fluctuating lift force, weakening the vibration of the flexible large-span roof. The negative pressures (suctions) in the inner and middle roof areas on the leeward side decrease for the blocked gap case. The positive pressure in the outer roof area generally increases along the windward direction, while the negative pressure decreases in other wind directions, when the roof inter-layer gaps are blocked. In the highest and transition roof areas, the fluctuating pressures increase for most wind directions, while in the lowest roof area, they decrease when the roof inter-layer gaps are blocked. The test and analysis results provide a valuable basis for the wind design of this kind of roof structures.

Influence of Inflow Turbulence on the Flow Characteristics around a Circular Cylinder

To study the influence of turbulence on the wind pressure and aerodynamic behavior of smooth circular cylinders, wind tunnel tests of a circular cylinder based on wind pressure testing were conducted for different wind speeds and turbulent flows. The tests obtained the characteristic parameters of mean wind pressure coefficient distribution, drag coefficient, lift coefficient and correlation of wind pressure for different turbulence intensities and of Reynolds numbers. These results were also compared with those obtained by previous researchers. The results show that the minimum drag coefficient in the turbulent flow is basically constant at approximate 0.4 and is not affected by the turbulence intensity. When the Reynolds number is in the critical regime, the lift coefficient increased sharply to 0.76 in the smooth flow, indicating that flow separation has an asymmetry; however, the asymmetry does not appear in the turbulent flow. Drag coefficient decreases sharply at a lower critical Reynolds number in the turbulent flow than in the smooth flow. In the smooth flow, the separation point is about 80° in the subcritical regime; it suddenly moves backwards in the critical regime and remains almost unchanged at about 140° in the supercritical regime. However, the angular position of the separation point will always be about 140° for turbulent flow for the Reynolds number in these three regimes. Turbulence intensity and Reynolds number have a significant effect on the correlation of wind pressures around the circular cylinder. Turbulence will weaken the positive correlation of the same side and also reduce the negative correlation between the two sides of the circular cylinder.

Optimization of RANS turbulence models using genetic algorithms to improve the prediction of wind pressure coefficients on low-rise buildings

Being associated with natural ventilation, the pressure distribution on surfaces is relevant for energy consumption, thermal comfort, and air quality in buildings. The aim of this work is to present a simulation-based optimization methodology to recalibrate the closure coefficients of Reynolds-averaged Navier-Stokes (RANS) turbulence models in order to improve the prediction of wind surface-averaged pressure coefficients on a wide range of isolated low-rise buildings. To accomplish this, genetic algorithms and Computational Fluid Dynamics (CFD) simulations are dynamically coupled to find the closure coefficients set which minimize the CFD prediction error regarding wind-tunnel experimental data. The methodology is applied to two turbulence models, the renormalization group k-epsilon model (RNG) and the Spalart-Allmaras model (SA), considering as target cases buildings with different roof types (flat, gable and hip) and wind incidence angles. In order to show the strength of the novel optimal sets of closure coefficients obtained, an exhaustive validation is performed over other low-rise buildings (52 new cases) which were not calibrated against. Results validate using the optimal sets because the recalibrated RNG and SA models decrease the prediction error between 11-64% and 8–45%, respectively, regarding using the standard ones.

Non-Gaussian Features of Local Wind Pressure for Typical Gable Roof of Low-rise Building

The non-Gaussian characteristics of local wind pressure of typical gable roof of low-rise building with a slop angle of 18.4° were monitored by means of the wind tunnel test under terrain roughness regimes of A,B and C. The probability density distribution features of wind pressure coefficient series are investigated, the characteristics of non-Gaussian zones distribution of wind pressure relative to different wind angles and different terrain conditions are analyzed and the relationships between non-Gaussian pressure and distinctions of flow field on roof are discussed. The studying results indicate that GEV distribution and Gamma distribution fit the probability density distribution of wind pressure coefficient better than Gaussian distribution and Lognormal distribution, but the fitting effect for long trailing tail part is undesirable, when skewness and kurtosis are large in magnitude (absolute value). The variation of terrain roughness and wind directions have significant influence on the distribution of non-Gaussian pressure regions on low-rise building roof. Under the oblique wind direction, the Gaussian pressure zone is divided into three sections along the approaching wind direction, along which the areas move with the change of terrain roughness regimes. The non-Gaussian features of wind pressure is positively related to mutual correlation coefficient of it’s time-history.

Study of Reserved Strength Capacity of Concrete Shell

Hyperbolic cooling towers have become the design standard for all natural-draft cooling towers because of their structural strength and minimum usage of material. The hyperbolic shape is particularly suited to cooling tower construction as the wide base provides a large space for the water and cooling system. As the tower widens out at the top, it supports the turbulent mixing as the heated air makes contact with the atmospheric air. Hyperbolic cooling tower is a tall structure with shells subjected to dead load and wind load. In absence of ground motion, wind becomes the major factor. In this study, 2 major models are studied with I and V column support. Each model is further divided into 2 models, i.e. one with SHELL element and another with SOLID element. All models were modelled and analyzed in ANSYS. The wind loads on these cooling tower have been calculated in the form of pressure by using the circumferentially distributed design wind pressure coefficients as given in IS: 11504 - 1985 code along with the design wind pressures at different levels as per IS: 875 (Part 3) - 1987 code. The analysis has been carried out using 8 noded shell element (SHELL281), 8 noded solid element (SOLID185) and 20 noded solid element (SOLID 186).

Numerical Investigation of Wind Pressure Coefficients for Photovoltaic Arrays Mounted on Building Roofs

The wind pressure distribution on the photovoltaic (PV) array is of great importance to the wind resistance design. The flow field related to the pressure can be influenced significantly by the turbulence induced by the building roof edge (Kopp et al., 2012) and it is essential to consider the building effect during the investigation. However, most CFD (computational fluid dynamics) investigations of wind pressure distribution on the PV array are limited to ground mounted PV array without the building. There is a necessity to extend the application of CFD method to flows around roof-mounted PV array. This study investigated the wind pressure distributions on PV arrays mounted on building roofs by means of Reynolds-averaged Navier-Stokes (RANS) approach using the FLUENT software. Since RANS models are sensitive to the fiow condition, several RANS models are adopted and the most accurate RANS model for predicting this type of flow is identified based on a comparison with the wind tunnel experimental results. The SST Κ-ω model can predict the highest net mean wind uplift located at panels upstream accurately and is further applied for the parameter analysis to facilitate the installation of roof-mounted PV array. Numerical simulations of the wind flow field for wind angles between 0° to 180° were carried out at intervals of 20°, and the resulted net pressure distributions were presented. The influences of tilt angles of the PV array were investigated and the pressure distributions of PV panels were related to the flow field. Moreover, the effects of clearance between the PV array and building roof on the flow fields and pressure distributions of the PV array related to PV array tilt angle are studied.

Can the inhalation exposure of a specific worker in a cross-ventilated factory be evaluated by time- and spatial-averaged contaminant concentration?

Industry implies economic growth; however, outdoor and indoor air pollution generated by industrial activities represents a widespread problem for the environment and human beings. In terms of human health, indoor air quality assessment has become essential in a society where people spend most of their time in indoor dwellings, as in the case of industry workers. Because indoor air quality is strongly affected by the outdoor environment, especially under natural ventilation conditions (e.g., cross-ventilation), a comprehensive analysis that includes outdoor atmospheric-urban environment is needed to reproduce realistic scenarios. In this context, computational fluid dynamics (CFD) is a useful tool. To perform a precise analysis of the inhalation exposure of factory workers to potential gas-phase contaminants in the working environment (i.e., inhaled dose of contaminants and potential effects), the human body and respiratory tract need to be integrated in the analysis. Therefore, in this study, we performed an integrated occupational inhalation exposure/toxicology assessment in a factory building that applies a computer simulated person (CSP), a virtual human respiratory tract and integrated physiologically-based toxicokinetic (PBTK) model to predict tissue dosimetry distribution. Outdoor airflow variation was transported into the enclosure through an hourly change in wind pressure coefficient to calculate transient ventilation rate and indoor contaminant concentration between 08:00 and 17:00 h. Thereafter, the time-averaged contaminant concentration calculated at the nares of the human body was employed in a steady state calculation of airflow and contaminant distribution inside the virtual respiratory tract. Subsequently, we predicted adsorbed contaminant in the first layer of tissue of the human airways; highest adsorption took place in the nasal cavity. Finally, based on the results of the comprehensive coupled numerical analysis performed using the CFD-CSP-PBTK model, we quantitatively discussed differences between the inhalation exposure concentration and representative contaminant concentration in the factory space (e.g., time and volume-averaged concentration).

New Test Method of Wind Pressure Coefficient Based on CAARC Standard Model Determined Using Vehicle Driving Wind

The driving characteristics of a vehicle, combined with a wind tunnel test and field measurement, can produce wind. This study proposes a transiting test method of building wind pressure under ideal road conditions via theoretical derivation and field testing. In this work, the basic theory of the transiting test was formulated, and the transiting test of a physical test platform was designed and assembled, and a software test system was established. The test data processing method was investigated and adopted for testing the mean wind pressure coefficient of the CAARC standard model’s typical measuring points. The influence of different speeds on the mean wind pressure coefficient was studied, and the difference of the mean wind pressure coefficient of repeated tests with the same speed was analyzed. Results showed the accuracy of the theoretical formula of the proposed transiting test, and the hardware and software systems were acceptable. The mean wind pressure coefficient of the typical measuring points of the standard model agreed well with the wind tunnel test results from relevant literature. Moreover, different speeds minimally affected the mean wind pressure coefficient. Thus, the technique is feasible under ideal road conditions. The transiting test method proposed in this study provides a new test technique for structural wind resistance research.