Abstract: 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 confirmed that these millimeter-scale groove-ridge structures would 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, accelerates jet momentum dissipation, and suppresses 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.