Drag reduction characteristics of an underwater air lubrication flat plate
To study the effect of ventilation jets on the resistance characteristics of underwater flat plates,the mix-ture multiphase flow model and Realizable k-ε turbulence model investigated the flow feather of a three-dimensional underwater flat vented jet,obtaining the structure and drag reduction characteristics of the gas-liquid flow field on the underwater flat surface.Numerical results showed that after the gas was injected,it was affected by the incom-ing flow and developed downstream closely along the wall.When the gas stably covered the plate wall,the resist-ance coefficient of the plate was 16.73%lower than the unventilated case.Because of the injection of gas on the wall boundary layer,the wall velocity gradient was increased,and the wall fluid viscosity coefficient was reduced;in the gas film coverage area(αl>80%),because the decrease in the fluid viscosity coefficient was much greater than the increase in the velocity gradient,the fluid viscosity coefficient played a decisive role in the drag reduction rate in the core region of the gas film;for the wall far from the core area of the gas film,the contribution of the tan-gential velocity gradient to the friction resistance coefficient was enhanced.
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