摘要
高速飞行器表面不可避免的存在突起物并形成复杂流场,从而引起飞行器气动特性和热载荷的变化;同时,突起物是流动控制的重要方法之一,合适的突起物形状及安装位置对于改善冲压发动机进气道性能有重要意义.本文采用基于纳米粒子的平面激光散射技术(NPLS)研究了马赫3.0来流边界层为层流的平板上三个不同高度圆台突起物绕流流场,主要关注了突起物后方的尾迹边界层,并采用高精度的显式五阶精度加权紧致非线性格式(WCNS-E-5)离散求解Navier-Stokes方程模拟了该流场.获得了超声速圆台绕流精细流场结构,观察到突起物后方尾迹区域边界层发展的过程.结合实验和数值模拟结果可以发现,当圆台高度接近或者小于当地边界层厚度时,突起物对边界层的扰动非常弱,圆台后方尾迹边界层能够维持较长距离的层流状态,在边界层转捩阶段也有清晰的发卡涡结构出现;反之,边界层受到的扰动明显增大,在突起物后方很快发展为湍流;风洞噪声对本文研究圆台引起的边界层扰动有一定影响,实验获得的边界层转捩位置要比数值结果靠前.基于NPLS流场图像,采用间歇性方法分析了圆台突起物后方边界层的特性,对于高度大于边界层厚度的圆台其间歇性曲线较为接近并且更加饱满,边界层的脉动也更为强烈.
Although high-speed vehicles are designed to be smooth, they tend to have some protuberances on their surfaces. Thus the aerodynamic characteristics and thermal loads are changed. Meanwhile, mounting protuberances on a flat plate is an important way of flow control, and appropriate structure and location of the protuberance can improve the performance of the scramjet inlet remarkably. The nanotracer planar laser scattering （NPLS） technique is used to test the flow field of Mach 3.0 supersonic flow over circular protuberances of different heights. In total three models are tested. And the second-order scheme and fifth-order weighted compact nonlinear scheme （WCNS-E-5） is adopted to simulate the flow field. Fine structures of supersonic flow over the circular protubernaces have been obtained and the development of boundary layer in the wake flow can be observed. By comparison, it may be concluded that the protuberance lower than the local thickness will have weak disburances on its boundary layer development, and the layer after reattachment can keep its laminar state within a long distance. During the transition many clear hairpin vortices can be distinguished. When the protuberance height is larger than the thickness of the boundary layer, and the later in the region of wake flow would develop into a turbulence quickly due to intense disturbances. The transition point observed from the experimental results lies closer to the protuberance, and this might be cansed by the noise from the walls of the wind tunnel. Intermittency analysis has been done for the boundary layer in the wake flow based on the NPLS images, and the results show that the intermittency curves of the two protuberances that are larger than the local boundary layer thickness are quite similar and fluctuations are strong.
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
2015年第5期296-303,共8页
Acta Physica Sinica
基金
国家自然科学基金(批准号:11302256
11172326)资助的课题~~
