Wind tunnel test research of internal pressure response induced by oblique flow for rigid structure with opening

Wind tunnel tests were conducted to study internal pressure response induced by oblique flow for rigid structure with opening. The dynamic internal pressures of rigid structure with single opening were tested induced by both uniform flow and turbulent flow in ZD-1 boundary wind tunnel of Zhejiang University. Rigid structure was made of steel plates, The internal volume is 0.0064m-3, the panel size is 500mm×500mm, an orifice with the area of 1256mm2 and the depth of 4mm was arranged in the middle of the panel, the shape of the orifice is square, circular and rectangular respectively with aspect ratio of 1:2. For uniform flow ,the turbulence intensity is less than 0.5% and the wind speed selected as 5m/s, 10m/s, 15m/s and 20m/s. For turbulent flow, the wind speed is 10m/s and the turbulence intensity is 10% and 20%. The enclosed opening external pressure and internal pressure of structure were tested respectively under the 0°~90° of wind angle with sampling frequency up to 625Hz.The inference of parameters such as wind angle, turbulence intensity, wind velocity, orifice characteristics were investigated. The characteristics of dynamic internal pressure induced by oblique flow were analyzed in emphases, and the mechanism of vortex-induced internal pressure resonance was explored preliminarily. The study show that, the difference of internal and external pressure coefficient in the uniform oblique flow for 55°~75° wind angle is more than 0.2, which confirm that there is drive phenomenon under the oblique flow, and the estimation of mean external wind pressure in opening as mean internal pressure will be dangerous. Vortex-induced internal pressure resonance will appear for rigid structure with opening induced by oblique flow for near 50° wind angle, which lead to fluctuating internal pressure increasing. The vortex shedding resonance effected by the growth of eddies across the orifice and the interaction with the Helmholtz resonance are the mean reasons for the existence of vortex induced internal pressure resonance. Parameter comparison test results show that, the smaller the turbulence intensity and the higher the wind speed, the greater the possibility of vortex-induced resonance. The occurrence of vortexinduced resonance can be inhibited for flat rectangular orifice.