Design and Experimental Investigation of a Small High-Speed Water Tunnel Test Section

To address the thermal management requirements of unmanned underwater vehicles (UUVs), this study designs a small high-speed water tunnel test section. Combining numerical simulations and experimental methods, we systematically investigate how outlet gauge pressure regulates flow structure and cooling performance from perspectives of vortex dynamics and turbulent energy scaling. Results demonstrate that increasing outlet pressure from 1.0 to 2.0 atm reduces system pressure loss by 26.60%, drag coefficient by 26.56%, and power consumption by 27.30%. The test section maintains flow uniformity below 1.0% with over 75% high-speed zone coverage, satisfying the ≥25 m/s design requirement. Mechanism analysis reveals that elevated pressure suppresses cavitation and boundary layer separation, attenuates large-scale vortex generation, and promotes turbulence transition to smaller scales, thereby optimizing energy transport and thermal uniformity. Experimental validation confirms the numerical model’s reliability in predicting flow characteristics, providing theoretical and technical support for advanced water tunnel design and battery thermal management optimization.