Study on Separation Bubble on the Constant Thickness Airfoil with Circular Leading Edge

实验研究了沿半径为10mm圆形前缘的等厚翼型的均匀流动和加速流动，研究了分离特性、分离泡结构、分离泡内流动特性以及表面压力与表面速度的关系。基于翼型厚度的雷诺数为2.65x10^4，攻角为0 5。结果如下：(1)边界层过渡区分离时，分离泡大尺度涡中心位于分离泡后半部分附近。分离泡后半段分离流线的弦向梯度大于分离泡前半段。在湍流边界层中分离时，这一现象正好相反。(2)对于再附着，从主流通过剪切涡向分离剪切层提供能量，从再附着点向分离泡向主流提供等于夹带量的反向流量。(3)边界层过渡区分离时，大尺度涡中心下游的雷诺数剪应力最大，湍流边界层分离时，大尺度涡中心上游的雷诺数剪应力最大。(4)在过渡区分离时，再附着点位于分离泡中恒压区后面的压力恢复区。在湍流边界层中分离时，在压力恢复完成后出现再附着点。(5)过渡区分离时压力波动最大的位置在再附着点附近，湍流边界层分离时压力波动最大的位置在再附着点上游。

Uniform flow and accelerated flow around the constant thickness airfoil with circular leading edge of 10mm radius has been studied experimentally on the characteristics of separation, the structure of separation bubble, the characteristics of flow in the separation bubble and the relation between surface pressure and surface velocity. Reynolds number based on airfoil thickness is 2.65x10^4 and angles of attack are changed 0ﾟ - 5ﾟ. The results are as follws.(1) In case of separation in transition region of boundary layr, the center of large-scale vortex in the separation bubble is found around the latter half of separation bubble. The chordwise gradient of separation-streamline at the latter half of separation bubble is larger than that at the front half of it. In case of separation in turbulent boundary layr, the phenomena are reversed.(2) Relating to the reattachment, the energy is supplied from main flow to separated shear layr by means of shear vortex, and the reversed flow volume equal to the entraining volume from separation bubble to main flow is supplied from reattachment point.(3) Reynolds shear stress become maximum downstream the center of large-scale vortex in case of separation in transition region of boundary layr, but upstream the center of large-scale vortex in case of separation in turbulent boundary layr.(4) In case of separation in transition region, the reattachment point is located in the pressure recovery region just behind constant pressure region in the separation bubble. In case of separation in turbulent boundary layr, the reattachment point appears after the completion of the pressure recovery.(5) Maximum pressure fluctuation occurs around the reattachment point in case of separation in transition region, but upstream the reattachment point in case of separation in turbulent boundary layr.