移动效应的下击暴流风场特性分析

稳态下击暴流风场研究已相对成熟,而实际下击暴流由于风暴移动,其风场是非稳态的。为了研究冲击风射流速度、移动速度对下击暴流风场特性的影响,采用冲击射流装置进行了移动下击暴流风场试验,并使用大涡模拟建立了移动喷口的冲击射流三维缩尺和足尺风场进行数值分析。结果表明:试验和模拟吻合较好,移动速度对峰值放大作用比较明显,射流速度对峰值大小影响不大;移动下击暴流风场具有风向转变和明显不对称的特点,移动速度对风暴前方近壁面水平风速具有显著的增大效应,但对风暴后方风速有一定程度的削减;下击暴流发展到稳定状态时的风剖面随高度增加先增大到最大值,然后迅速减小,最大风速出现在风剖面下端;曲线峰值所在位置和下降段所持续的时间与移动速度和射流速度大致满足一定的比例关系。

Downburst wind field characteristics under moving effect

Downburst wind field study under steady state is relatively mature.Due to storm moving,the actual downburst wind field is unsteady.In order to study effects of jet-flow velocity and translational velocity on characteristics of downburst wind field,a test for downburst wind field under moving was conducted with an impinging jet device.The large eddy simulation(LES)was used to build 3-D reduced scale and full-scale wind fields of impinging jet at moving nozzle to do numerical analysis.The results showed that the numerical simulation results agree well with test ones;moving speed has an obvious peak amplification action,and jet velocity has little effect on peak value;the translating downburst wind field has features of wind shift and obvious asymmetry,translating speed has a significant amplification effect on the horizontal wind speed near wall ahead of storm,but it causes some reduction in wind speed behind storm;when the downburst develops to enter a steady state,the wind profile increases to the maximum firstly and then decreases rapidly with increase in its height,the maximum wind speed appears at the lower end of the wind profile;the curve peak position and the duration of the curve descending segment are related to moving velocity and jet one in a certain proportion.