激光测速测量湍流分离-再附流动

LDV MEASUREMENT OF A TURBULENT SEPARATION-REATTACHMENT FLOW

湍流边界层分离研究是当前流体力学中难度极大的课题。有关的试验比较罕见,其重要原因是接触式测速技术对流场有干扰且无方向敏感性,因而难以获得可信数据。激光多普勒测速(LDV)作为非接触测速技术,可以有效地测量间歇反流特征,因此越来越多的研究者倾向于应用LDV研究湍流分离流。迄今为止,应用LDV对分离流的研究一般侧重于分离过程。对整个湍流分离-再附过程进行完整的测量尚不多见。本试验采用二维LDV系统详细地测量了二维非对称曲壁扩压器内的湍流分离-再附流动。

Detailed investigation of a turbulent separation-reatta-chment flow in a 2-D curved-wall diffuser using TSI model 9100-7, two-color, dual-beam Laser Doppler Velocimeter System. This separation occurs under strong adverse pressure gradient on a convex surface with large curvature, and the separated shear layer reattaches downstream where the adverse pressure gradient becomes milder or under the natural relaxation condition, simulating the actual flows in some engineering applications.Mean velocities U, V and Reynolds stresses u2, v2 and -uv are presented. The preliminary analysis shows that the experimental results are reliable. The entire flow field can be divided into five regions. The reatiaching flow is about twice the length of the separating zone. Due to the separation, the streamwise curvature induces a significant normal pressure gradient near the incipient detachment. It is found that there exists a second peak on u2, as well as a negative of (-uv ) having the same order of magnitude as (-uv)max, downstream of the transitory detachment.