Aerodynamic Internal Pressure Loads Applied On Nonstructural Elements under Wind Gusts (original) (raw)
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Aerodynamic-Internal-Pressure-Loads-Applied-On-Nonstructural-Elements-under-Wind-Gusts.pdf
Vent holes can be used to reduce the aerodynamic pressure loads on nonstructural elements of buildings. The analysis of these loads applied on nonstructural elements of buildings (window panes, closure panels, etc.) with vent holes, under gusty wind conditions, have been studied both experimentally and employing a theoretical model. An experimental setup based on an open circuit, closed test section, and low speed wind tunnel, designed and built at the Instituto de Microgravedad "Ignacio Da Riva" of the Universidad Politécnica de Madrid (IDR/UPM) has been used. A mechanism in the wind tunnel generates sinusoidal gusty winds inside the test section. Theoretical predictions of the pressure loads have been obtained using a mathematical model based on the mass conservation equation and polytropic law gas evolution. In the experimental setup, an air reservoir with a vent hole has been selected as a model to simulate the internal pressure loads acting on the walls of a building under a tangential unsteady (gusty) flow. The pressure jumps developed across the vent holes have been studied as a function of vent hole size, air reservoir volume, and gust frequency. In this work, the results for the case of small pressure jumps across the vent hole have been presented, which is the case of most practical interest, in order to reduce the pressure load on the elements. The evolution of the pressure loss coefficient ξ, at unsteady flow conditions has been studied, and it has been found that its value is not constant in a gusty wind, but depends both on the frequency of the gust and on the direction of the flow through the vent hole (either inhalation or exhalation).
Natural ventilation of buildings can be made by employing pressure difference among different parts of buildings induced by external wind. Wind-catching parts have positive pressure while lee parts have negative one. When there are openings on both sides, airflow is induced through the building. In this study, experiments and numerical computations were conducted to study wind-driven ventilation through two-dimensional scaled models of buildings. The purpose is to examine effects of: 1) pitch angle (p) of the roof, and 2) relative positions of openings on both sides on induced flow-rate through the building. The experiments were performed in the wind tunnel at the Laboratory of Fluid Mechanics of Ho Chi Minh City University of Technology. The scaled models of buildings had dimensions of order of 10cm. Velocities of wind passing the model and induced airflow through the models were measured with a hot-wire anemometer. The computations were made by a CFD (computational fluid dynamics) technique. Governing equations were discretized with Finite Volume Method. Standard κ-ε model was used for turbulence. Computed domain included both the buildings and appropriate extended space.
Experimental Investigation on the Wind-Induced Pressures on C-Shaped Buildings
The present work focuses on the outcome of experimental investigation of pressure coefficients on different faces of C-shaped building models. An extensive experimentation was carried out to obtain a pressure coefficient over the surface of the models of varying configurations, corner curvature and angle of incidence between 0° to 180° at an interval of 30° in a subsonic open circuit wind tunnel. Four different configurations of C-shaped models of varying curvatures were tested. The models were made of perspex sheets. The recorded data of pressure at the located pressure tapings enabled determination of pressure coefficient and the study of the variation of pressure coefficient on the surfaces with wind angles and corner curvature. It has been observed that the pressure coefficient at a location on a surface varies significantly with the angle of incidence and the curvature of the surfaces. Also, the extent of maximum and minimum pressure zones have been found to change with the curvature and the wind direction.
A WIND TUNNEL EXPERIMENT OF WIND FORCED NATURAL VENTILATION OF A DETACHED HOUSE
Wind-induced natural ventilation of a city house is strongly influenced by the adjoining buildings. In this paper, a wind tunnel experiment using a one storey model house has been carried out to clarify the influence of surroundings on the distribution of the wind pressure coefficients Cp around the house. In addition, the natural ventilation rate is calculated using a method which considers the distribution of Cp and leakage area around the house. The effect of surroundings on the natural ventilation has been studied by changing the density of surrounding buildings, i.e. building coverage, K.
The present work deals with numerical simulation of external and internal flows induced by wind in and around a prismatic building using ANSYS 14.0 code. The internal flow within a building is generated by wind entering the building through openings like doors, windows etc. as well as buoyancy force generated by thermally induced convection. Internal flow interacts with external flow to produce total wind load on the building which may cause building failure or structural instability under stormy conditions. Also natural ventilation system inside the building may be affected by the interaction necessitating design modifications. It is evident from the present analysis that interaction of external and internal pressures may magnify the wind load on the roof which has very harmful effect. The magnitude of total wind load depends on number of openings, shape of the building. The streamline pattern clearly shows the wind movement inside the building which is important from natural ventilation point of view.
Parametric analysis of the wind-driven ventilation potential of buildings with rectangular layout
Building Services Engineering Research and Technology, 2018
A method to evaluate the wind-driven ventilation potential of buildings is proposed and some schematic examples are given. Two indicators of such potential are put forward: the first concerning the pressure difference between spots (openings) on the facades and the second concerning the ratio between this pressure difference and a simplified measure of the pressure loss by the internal air flow. These indicators allow one to compare shapes and orientations and can help finding the most appropriate ones during a preliminary stage of the design of a naturally ventilated building. To present the proposal, a two-dimensional computational fluid dynamics parametric model of a schematic building is set, the parameters of which are the aspect ratio of the building's rectangular plan and the wind relative direction. The computational fluid dynamics simulations are supported by literature benchmarks and by qualitative experiments in a wind tunnel. Using this model, the pressure field is c...
Wind-driven natural ventilation for buildings with two openings on the same wall.
This study uses wind tunnel experiments to investigate the wind-driven ventilation for buildings with two openings on a single wall. The exchange rates are measured by the tracer gas decay method under different external wind speeds, directions and opening sizes. The experimental results indicate that the time-averaged pressure difference across the openings is much larger than the fluctuating pressure when the wind direction is  = 22.5-45 • , and the ventilation rate can be predicted by the orifice equation. When the wind direction is  = 0 • and 67.5-180 • , the pressure difference across the openings is insignificant and the fluctuating pressure entrains air across the openings. The exchange rate is proportional to the root-mean-square of the pressure fluctuation. Furthermore, the dimensionless exchange rate of the shear-induced ventilation (wind is parallel to the openings) is found to be independent of the wind speed, opening area and location. The exchange rate for buildings with an internal partition is lower than that without a partition when the wind direction is  = 0-90 • . A semi-empirical prediction model is proposed to calculate the exchange rate by incorporating the time-averaged pressure difference and pressure fluctuation. The application of the prediction model to compute the air change rate (ACH) is also discussed.
Internal pressure in low and medium rise buildings subjected to high winds
2011
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Acta Scientiarum. Technology, 2018
Wind tunnel experiments and Computational Fluid Dynamics (CFD) simulations are used to analyze natural ventilation in a sawtooth roof building. A 1:10 scale model is tested in an atmospheric boundary layer wind tunnel. The CFD simulations are performed with Ansys CFX software. The aim of this study is to evaluate the reliability of CFD simulation in predicting pressure data at opening height in a sawtooth roof building with wind tunnel data. The model is evaluated for prevailing wind in five directions: 0 and 45° (air extractor sheds), 90° (neutral situation) and 135 and 180° (air collector sheds). The computational grid resolution shows that the inclusion of prisms and the increase of the grid refinement in the building's surface cause insignificant differences in Cp (wind pressure coefficient). In general, the error values below 10% indicate a good agreement between CFD simulations and wind tunnel data.