分离泡诱导下平屋盖表面风压特性研究

Wind pressure characteristics on a flat roof induced by separation bubble

通过平屋盖刚性模型风洞测压试验,研究了分离泡不同部位所诱导的风压特性。从分离泡内、外部流场运动角度,分析了各部位风压特性的产生机理,研究了平屋盖表面平均和脉动风压系数分布、顺风向和横风向风压的相关性。给出了顺风向各点的脉动风压谱及相位角特征,并对分离泡及其诱导的风压特性进行了讨论。结果表明:在分离泡前部,顺风向风压相关性显著,风压脉动体现为低频特征,风压系数极值(极值吸力)出现在20%再附长度处;在分离泡中部,再附长度约一半位置处为风压脉动特性的转捩点,即转捩点上游风压脉动为低速传播,下游风压脉动为高速传播,且上、下游风压脉动呈现负相关和反相位的特征;转捩点处脉动风压系数出现最大值;在分离泡再附区,风压的高频脉动降低了其横向相关性,峰值因子最小值出现在再附点处。

This paper presents an investigation into the characteristics of wind pressure induced by different parts of separation bubbles through the wind tunnel test on a large-span flat roof. Production mechanism of wind pressure characterestics at each part of the flat roof was analyzed in terms of the flow motion inside and outside the seperation bubbles. The distribution of mean and fluctuating pressure coefficients was firstly presented,followed by an analysis of the correlations of longitudinal and transverse pressure fluctuations. The wind fluctuating pressure spectra and phase angles were then presented for longitudinal taps. Lastly,the characteristics of wind pressure induced by separation bubbles were discussed. The test results show that at the forepart of separation bubbles,significant correlation of longitudinal wind pressure and low-frequency wind fluctuations are observed. The statistical peak suction is detected at a distance of 0. 2 times reattachment length from the separation point. At the central part,the maximum fluctuating wind pressure occurs at approximately the midpoint of the reattachment length,which is the transition point for the wind fluctuation from low-speed propagation to high-speed propagation. The upstream and downstream wind fluctuations of the transition point are found to be negatively correlated and out of phase. At the reattachment region,the correlation in the transverse direction is weakened by high-frequency wind fluctuations. The minimum peak factor occurs at the reattachment point.