以寒鸦为测试对象。在风洞中,采用LaVision公司的时间分辨2D3C立体PIV测量系统,对开槽翼尖的多核漩涡对鸟类滑翔和扑翼飞行的支撑作用进行了研究。实验装置包括一台英国Litron公司的LDY304PIV高重复频率激光器,两台Imager pro HS 4M型高速相机,和DaVis8.4软件平台构成。
We report particle image velocimetry measurements of the collision of a vortex ring with a heatedwall kept at constant temperature. We consider the case when both the vortex ring and the thermalboundary layer generated by the vertical heated wall are stable and laminar prior to any interaction.The impingement process can be divided into two parts. sid A ring-driven stage, where the vortexring grows in diameter while approaching the wall and therefore it sweeps progressively anincreased surface on the wall. siid A boundary layer-driven stage, where the vortex ring movesupward due to the thermal convective motion generated by the heated wall. In some cases, thehead-on collision triggers the ring’s azimuthal instability as revealed by the formation of vorticalstructures arranged on a wavy starlike pattern and confirmed by flow visualizations. A singlecollision generates important velocity gradients and shear stresses along the wall accompanied withthe creation of local vorticity normal to the vertical heated wall. Peak wall shear stresses occur nearthe point of impact of the vortex ring core.