Numerical Investigation About The Effects Of The Wind Direction On WDR Distribution On Windward Building(S) Facades

In recent years, the frequent extreme weather has strengthened WDR’s destructivepower over buildings, which can cause seepage, erosion, or change their inner humidityand temperature. In severe cases, it can also increase the load on buildings that cannotbe ignored. Therefore, knowledge of the quantity of WDR and the distribution of rainload impinging on building facades is necessary in building design for effectiveresistance to WDR.On the basis of previous research, CFD numerical model will reveal the effect law ofvarious wind directions on WDR distribution of group buildings’ windward facades bymodeling fundamental equation with averaged Navier-Stokes equation and standard k-ε turbulence. In this process, Euler-Euler multiphase flow model can figure out thevolume fraction and velocity of raindrop by using User Defined Function (UDF) tochange the wall condition, combined with the spectrum and terminal velocity formula ofraindrop.Firstly, the research on rain pressure and catch ratio of a single building in differentwind directions, speeds and rainfall intensities shows that as the wind speed and rainfallintensity grow, WDR rain load and catch ratio increase as well, and they will meetmaximal values on the top of two sides. The point where the maximum appears alsomoves to the corner near wind origin as the wind direction changes. In the direction of0degree, the worst working condition comes with the maximal values of catch ratio andrain pressure occurring simultaneously. The wind direction of45degrees can beconsidered as the knee point where the WDR effects begin to heighten for that when thewind direction turns to30and45degrees, both the average catch ratio and rain pressureare lowered, but not much; then to60degrees, their reduction accelerates.Then a numerical simulation with different WDR conditions of twin buildings, ofwhich the shorter is in the front and the taller is at the back, indicates that there exists asimilar WDR distribution law between a single building and twin buildings. When inwind direction of0degree, WDR effect gradually enhances on the back one from thecenter to four edges. Where the maximal values appear are also at the top of two sidesand move to the corner near wind origin as the wind direction changes. However, WDRaffects the taller more at the height accordant with the front itself. Lastly, the simulationof WDR effect on a building group of three rows and two lines in different wind directions works out its law and characteristics of WDR distribution: buildings in thefront are similar to a single building, but their maximum rain pressure and catch ratioare smaller than those of the followed row. While the wind rotates from0to60degrees,the points where the maximums appear on each building also move from top of the twosides symmetrically to the corner closer to the wind origin, but WDR effect is moreobvious at the corner near the ground and farther from wind origin. When in direction of45degrees, the maximal catch ratio of the corner can be about90%of the wholefacades, and the rain pressure99%. From all the above, the research performed in thispaper will introduce a reference for weather resistance and water proofing in both singlebuilding and group buildings design.