The Hydrodynamic Performance Numerical Analysis Of The Water-entry And Water-exit Phenomenon Of The Section Of Surface Piercing Propeller

With the increase of the importance of high-speed craft in recent years,the surface piercing propeller device has been more and more widely used because of its high efficiency,low appendage resistance,no cavitation erosion phenomenon and so on.When the surface piercing propeller works,the lift of the free surface and the formation of ventilation cavity often happen near the suction surface.Due to the special working environment of surface piercing propeller,the prediction of hydrodynamic performance of surface piercing propeller has always been a difficult problem,which restricts the theoretical development of surface piercing propeller.The study of surface piercing propeller in blade profile form,on the one hand,is a good method to study the details of flow field,on the other hand,is an ingenious way to reduce the amount of calculation,thus a large number of calculation results can be obtained for mechanism analysis.In this paper,the hydrodynamic characteristics and ventilation characteristics of the surface piercing propeller section are analyzed by using the finite volume method（FVM method）.Through STAR-CCM+software,the water entry mechanism model and periodic water entry model are established respectively.On the basis of verifying the feasibility of this numerical method,the hydrodynamic characteristics are analyzed deeply by changing the parameters such as section position,oblique flow angle,immersion depth ratio and so on.The calculated results are consistent with the open water characteristics of surface piercing propeller,so the mechanism analysis results of flow field characteristics and ventilation characteristics can support the hydrodynamic performance prediction and optimization design of surface piercing propellers in the future.The calculation results show that in the process of increasing the speed coefficient,the contraction of the ventilation cavity will happen with the process of water entry and water exit,which makes the ventilation state transition from the fully ventilated state to the partial ventilation state,and the peak values of the transverse force coefficient K_Xand efficiency will correspond to a position with higher speed coefficient.In addition,the changes of immersion depth ratio and oblique flow angle will also have a very complex influence.Finally,on this basis,a parameterized modeling method suitable for surface piercing propeller blade profile is proposed,and its hydrodynamic characteristics with variable parameters are studied by changing the edge curvature and edge thickness of the surface piercing propeller blade section.A set of diagrams for supporting the section design of surface piercing propeller are drawn.The results show that with the increase of the curvature K₁ and the thickness of the trailing edge,the ventilation characteristics and the transverse force coefficient K_X will be improved,but the efficiency will be sacrificed a bit because the pressure surface of the section of the surface piercing propeller increases with the load on the edge.In order to optimize different surface piercing blade profile models,the TOPSIS superior and inferior solution distance method is adopted in this paper.By calculating the Euclidean distance between the optimization objective and the ideal scheme,the variable parameter models of 54kinds of surface piercing propeller blade sections are evaluated and optimized.finally,two of the schemes are selected as the optimal scheme.