The Influence Of Jet Control Parameters On Cavitation Flow Control

The shedding of attached cavitation will increase the instability of the flow field and cause a series of hazards such as noise and vibration of hydraulic machinery.Therefore,the control of cavitation flow is particularly important.Aiming at the cavitation control method of opening jet water holes on the suction surface of the hydrofoil,this paper takes the NACA66(MOD)hydrofoil as the research object,combining high-speed camera technology and numerical simulation methods to study the correspondence between different jet parameters and cavitation suppression effects.Determine the best combination of jet parameters and analyze the mechanism of jet flow to inhibit cavitation.High-speed full-flow field camera was used to study the cavitation suppression effect of three different structures of jet hydrofoil in cloud cavitation and transitional cavitation.It was found that the jet flow,jet position,and jet angle have different degrees of influence on the cavitation suppression effect,and there is the best combination of jet parameters.Based on the experimental results,through orthogonal design combined with numerical simulation,the density-corrected DCM turbulence model combined with the Zwart-GerberBelamri cavitation model was selected to carry out the research on the influence of multiple jet parameters on the effect of cavitation suppression and hydrodynamic performance under cloud cavitation.The results show that different jet parameters have different effects on the cavity volume and the lift-drag ratio of the hydrofoil.The sensitivity of the two indexes to the jet parameters is different,and it is impossible to achieve the best values of both indexes at the same time.But the drop in lift-drag ratio of the jet hydrofoil is very small.Therefore,the hydrodynamic performance is used as a constraint to study the best combination of jet parameters.The study of the mechanism of cavitation suppression found that the jet can improve the surface pressure distribution of the hydrofoil and block the return jet.The thickness of the boundary layer of the jet hydrofoil surface velocity and the strength of the return jet are reduced,and the attached cavitation does not show a large-scale shedding phenomenon.Through the identification of the source term and vortex structure of the cavitation flow field vorticity transport equation,it is found that the velocity gradient generated by the jet fluid is the main source of the vorticity at the jet hole position,and the flow field structure here is unstable.The chordal vortex structure formed by the jet and the spanwise vortex structure formed by the back jet and the gas-liquid interface shear each other,which separates the attached cavities in advance,avoiding the reattachment of attached cavitation behind the jet hole.The broken cavitation group quickly collapsed when moving to the tail of the hydrofoil under the action of the main flow,and the high-pressure pressure shock occurred in the area near the jet hole.The study of the best combination of jet parameters has a certain guiding effect on the application of jets to suppress cavitation in hydraulic machinery.