下击暴流出流段非稳态风场的大气边界层风洞模拟

为在风洞实验室中实现大尺度下击暴流出流段风场模拟，基于平面壁面射流方法，设计制作了一套下击暴流出流段非稳态风场的模拟装置。通过增加壁面射流喷口及风机，得到下击暴流的水平平均风速竖向剖面。采用快开阀门形成非稳态的突变风场，与安德鲁斯空军基地下击暴流实测数据对比，对模拟装置进行了验证。结果表明:设计的基于壁面射流的下击暴流模拟装置能够有效模拟下击暴流出流段风场；在稳态条件下，装置能够形成较为均匀的二维平面壁面射流流场，在完全发展区域，能够得到与典型下击暴流竖向平均风速剖面较为吻合的结果；采用非稳态的壁面射流装置，能够得到非常接近实际下击暴流的时变平均风速。

Experimental study on simulation of unsteady downburst outflow in atmospheric boundary layer wind tunnel

In order to realize large-scale unsteady simulation of the downburst outflow in the atmospheric boundary layer wind tunnel, a set of large-scale test facility for the transient downburst outflow was designed and manufactured based on the plane wall jet method. The vertical profile of the horizontal mean wind velocity of the downburst was obtained by adding the wall jet device, and then the unsteady wind field was formed by using a fast-opening valve. The wind velocity record from the Andrews Air Force Base downburst is employed for verification of the experimental procedure. The results show that the simulation device of downburst based on wall jet can effectively simulate the wind field of downburst outflow. Under steady-state conditions, the test device can form a relatively uniform two-dimensional wall jet flow field, and in the fully developed area, the results are consistent with the vertical mean wind profile of the typical downburst flow. The time-varying mean wind velocity time history which is very close to the actual downburst record can be obtained by using the unsteady wall jet device.