Estimation of drag coefficient of various structures using computational fluid dynamics

Abstract

The objective of this research work is to study the distribution of wind pressure on inclined and curved surfaces by using numerical techniques for solving the fluid dynamic equations, and present a comparative study between the output results and resulting records of wind tunnel test and the assigned values at code standard. A verification study is done to present a comparison between computational fluid dynamics (CFD) method and other earlier numerical computation done at past researches. The applied method includes single span short and long gable structure with double slopes, cylindrical silos, saw tooth, dome and truss. For gable buildings, the different roof zones coefficients of pressure have been focused to compare the application of CFD technique with the international wind standards and codes of practice such as EN 1991-2-4 and ASCE. The most current provisions for calculating the wind induced pressure on buildings extracted from boundary layer wind tunnel tests. The wind tunnel experiments are expensive and not always available for design engineers. This research is an attempt to maximize the benefit of using the available numerical techniques to extend the available database for wind codes provisions. The calculated mean pressure coefficient generally agrees with the existing empirical relations although the pressure distribution is not the same, at first the comparative study showed that the values of the pressure coefficients predicted from the numerical technique agrees very well with the experimental corresponding values. After that, the comparison between the CFD values of coefficients of pressure supported by the experimental values shows the ASCE code values over estimates the design values. The study results show good description of air flow using the CFD technique, besides, it shows a different distribution of pressure with wind acting at oblique direction that must be evaluated with new values, not to be calculated as a component from the perpendicular acting wind. All the concluded values, and the recommended distribution of pressure coefficient is summarized at the last chapter showing the recommended precautions that must be taken at future researches.