The Study Of Wind Pressures On Building Under Steady-state Impinging Jet Flow

Downburst is the disasters phenomenon in thunderstorm weather that sinking airflow slammed into the ground and spread to cause short-term wind on the ground. It can seriously destructive the structures. In the building structures load code for the design of our country, the design wind load is based on ordinary atmospheric boundary layer wind field. Actually the velocity profiles of downburst wind field are of great difference from those of the normal atmospheric boundary layer wind field, And the building surface wind pressure under the action of downburst and the common boundary layer wind field also shows different distribution regular. So the wind load of building under downburst can’t simply calculated by the load code. At present, the systematic study about the wind pressure characteristics of different categories building structure under the action of downburst is lack. In this paper, the author build the impingement model to study the building structure wind pressure character under the action of steady state impingement through physical experiment and numerical analysis. Some preliminary research and achievements show that:① Conduct rigid construction model wind tunnel test under the action of the impact jet pressure, and the parameters including height to width ratio and width to thickness ratio. Preliminarily study the influence of different height to width ratio and width to thickness ratio on wind pressure characteristics of high-rise building and low building.② By using three dimensional scale numerical model in proportion to experiment, verify and supple the impingement physical test condition. Based on discussing the applicability of the simulation of different turbulence models under the action of impingement wind pressure, explore the influence law of various building parameters on the characteristics of wind pressure.③Analysis the influence factors of different categories through the wind tunnel experiment and CFD numerical simulation.(including height to width ratio and width to thickness ratio of high-rise building and side length of low building, which is the width of the wind pressure surface) It turned out that: height to width ratio has a great influence on the surface wind pressure of high-rise building, especially on the construction side, lee side and the top side. With the increase of height to width ratio, the absolute value of the surface wind pressure coefficient decreases, but height to width ratio did not significantly influent the pressure coefficient on the windward side; width to thickness ratio of high-rise building has a great influence on the surface wind pressure. For the construction side and the top surface, with the increase of width to thickness ratio, the absolute value of surface wind pressure coefficient decreases, but on the lee side of the building, the absolute value of surface wind pressure coefficient increases, and width to thickness ratio did not significantly influent the pressure coefficient on the windward side; length of low rise buildings also have great influence especially on the construction side, lee side and the top side. The length is longer, the width of the windward side is more wide, so the wind pressure coefficient reduces, and length has no significant impact on the wind pressure coefficient on windward side.