Interplay Between Shear Layer Dynamics And Cavitation In Turbulent Flows On Microfluidic Chips: A Numerical And Experimental Study

Cavitation, the local evaporation and re-condensation of liquids due to pressure drops,significantly impacts engineering systems, necessitating a deep understanding for reliabledesign. This thesis presents a comprehensive investigation into the complex interactionof compressible cavitating flows with turbulent shear layers in microscale BFSconfigurations. Our methodology integrates advanced computational fluid dynamics withexperimental analysis. We employed a custom three-dimensional fully compressiblecavitation solver within a Large Eddy Simulation (LES) framework. This solver,leveraging an all-Mach Riemann approximation-based scheme to accurately capturecomplex density, pressure wave dynamics, and phase change across varying Machnumber regimes. We utilized both functional (WALES) and advanced mixed Subgrid-Scale (SGS) models to robustly simulate turbulence across scales. Key findings revealthat cavitation profoundly alters turbulent flow, reducing shear layer growth, delayingreattachment, and modifying Reynolds stresses and pressure fluctuations through vaporcollapse. We identified dominant low-frequency modes associated with reattachmentdisplacement and distinct vapor transport mechanisms. Furthermore, riblet-equippedsurfaces control incoming turbulence: they shift Turbulence Kinetic Energy (TKE)transport, modify Reynolds stress anisotropy, and promote larger, slower coherentstructures. These riblet-induced turbulent changes directly affect cavitation dynamics andcharacteristics. Experimentally, the study provides the first insights into shear cavitationin a microscale BFS. We observed unique microscale shedding modes influenced byvortex strength and pressure waves. This thesis advances the understanding of turbulentcavitating flows, demonstrating that comprehensive numerical and experimentalapproaches are essential for designing and optimizing microfluidic and energy systems.