离散粗糙元诱发边界层转捩的实验研究

针对直升机转子叶片模型表面离散粗糙元诱发边界层转捩问题开展了实验研究，分析不同雷诺数下粗糙元尺寸参数对转捩位置的影响。实验在中航工业气动院直升机转子叶片模拟装置进行，在模型转子叶片表面布置不同尺寸的离散柱状粗糙元，利用红外热像技术探测边界层转捩，并提出一种基于湍流／层流区域面积比的转捩位置判定准则，目的是实现边界层转捩位置自动识别，进而分析粗糙元尺寸参数对转捩位置的影响。实验转速为300至600 r／m，对应叶尖切向速度为25～40 m／s。实现了对旋转叶片边界层转捩位置的定量测量，通过实验验证，转捩位置判定算法正确可靠，初步得到了不同高度 DRE 诱发转捩位置与雷诺数之间的关系，随着粗糙元高度的增加，转捩位置逐渐靠前。

Experimental investigation on boundary layer transition induced by distributed roughness elements

An experimental study was undertaken to understand the problem of roughness-in-duced boundary layer transition and the sensitivity of boundary layer to the dimensions of DRE (distributed roughness elements).The distances between the DRE and the transition locations in different Reynolds numbers are considered.Experiments were conducted in the rotor blade whirl tower at AVIC ARI.Infrared thermography was employed to detect boundary layer transition on the rotor blade.In order to investigate the impact of the parameters of roughness elements on transition position,a new method was developed to measure the boundary layer transition posi-tion quantitatively.A method based on the ratio of turbulent and laminar areas was used to esti-mate the downstream transition locations.Seven rotational speeds between 300 rpm and 600 rpm were tested with leading to tip speeds betweenVtip=25 m/s and Vtip=40 m/s respectively.The results showed that,the IRT technique can be used to measure boundary layer transition on the rotor blade of a helicopter or rotor wings.The transition detection method based on the ratio of turbulent and laminar areas is accurate and reliable.The relationship of transition length induced by different hight of DRE and Reynolds number is gained preliminary,and as the height of roughness elements increase,the transition length is decreased.