后向台阶层流边界层分离实验研究

本文应用偏振差动式激光测速仪对后向台阶层流边界层分离、再附及发展为湍流边界层的整个过程进行了精细的量测,得到了时均速度、湍流强度等的分布特性。我们发现,在本实验条件下,层流边界层分离后在再附点处为过渡流,进一步发展最后形成湍流边界层。在湍流边界层区域,流速分布遵循对数律,但积分常数比平板湍流边界层中所得值要大。

AN EXPERIMENTAL INVESTIGATION ON LAMINAR BOUNDARY LAYER SEPARATION OVER A BACKWARD-FACING STEP

The differential LDA system has been used to measure the laminar boundary layer separation , reattachment and redevelopment up to turbulent boundary layer over a backward-facing step. The distributions of mean velocity and turbulent intensity are obtained. It is found that,in the present experiment, the flow is transitional boundary layer at the reattachment position, which further develope untill turbulent boundary layer was formed. In the turbulent boundary layer region,the distribution of mean velocity obeys the "log-law" except the greater value of in-tegeral constant in comparision with that obtained in turbulent boundary layer over a flat plate.