编织表面横向射流的近壁流动特性及旋涡演化过程实验研究OA

Ceramic Matrix Composites(CMCs)have emerged as a potential material for next-generation turbine blades due to their exceptional high-temperature resistance.Unlike conventional alloy blades,their unique weaving methods create periodic macro-scale surface roughness with distinct topological features.Previous studies have confirmed that these millimeter-scale groove-ridge structures significantly impact film cooling performance.However,systematic experimental investigation remains insufficient regarding the underlying flow mechanisms,particularly how woven-surface-induced near-wall flow characteristics affect the film cooling.This study models the problem as a jet in crossflow over woven surfaces and then conducts a Refractive-Index-Matching Particle-Image-Velocimetry(RIM-PIV)experiment.By precisely matching the refractive indices of fluid and solid wall,this technique overcomes conventional PIV limitations in near-wall measurements caused by laser reflection and optical distortion,enabling a precise resolution of the near-wall flow field.Results demonstrate that the woven surfaces substantially enhance spatiotemporal instabilities of the near-wall flow,and the swirling strength of the flow is particularly intensified over the ridge structures.The woven surfaces increase upstream hairpin vortex generation,while the ridge-induced lifting flow promotes the vortex detachment.These enhanced vortices intensify the fragmentation of shear vortices in the jet,accelerate jet momentum dissipation,and suppress the elevation of the jet.This leads to a reduced turbulent kinetic energy of the jet,and an attenuation of the windward-side Reynolds shear stress.Furthermore,strengthened interactions between the near-wall shear vortices in the jet and the downstream near-wall vortices lead to significantly enhanced flow instability and intensified shear stress in the jet wake region.