Numerical Simulation Of The Hydrodynamic Performance Of Propeller Beneath A Free Surface

Ventilation is a phenomenon of air ingestion that occurs beneath the free surface visibly,and the numerical simulation of ventilation phenomenon is more difficult due to the appearance of air cavities,spindrift and waves.The occurrence of ventilation can cause the performance of the propeller to change even mutate,which affects the normal operation of the propulsion system seriously,and also causes vibration and noise.The propeller working in the non-uniform flow field can cause severe vibration of hull,which sometimes affects the safety sailing of the ship.It is extremely significant to predict the exciting force generated by the propeller in the flow field correctlyIn this paper,the propeller 4381 is used as the main study object,and the numerical pool model is established.The numerical simulation of the hydrodynamic performance of the propeller beneath the free surface was carried out,and the propeller induced pulsating pressure was predicted based on the RANS method and the VOF modelIn order to verify the accuracy of the calculation method in this paper,three grids comprising different quantities of grid cells were employed to verified grid independence firstly.The result showed the good agreement between the simulated values and experimental values.The calculation precision is satisfactory,which provides reasonable support for the numerical simulation in this paperThe oblique flow is a simple non-uniform flow relatively.In order to analyze the hydrodynamic performance of the propeller working beneath the free surface and the induced pulsating pressure in the oblique flow,the numerical simulation of the unsteady hydrodynamic performance of propeller 4381 at different oblique flow angles was carried out.The effects of the oblique flow angle,the advance coefficient and the immersion depth on the thrust,torque,transverse force,vertical force and velocity field of the propeller were analyzed.The ventilation phenomenon and vortex trajectory of the propeller were discussed in the oblique flow conditions,and the pressure data of the monitoring points in different conditions was recorded to summarize the rule of influence of the oblique flow angle,the advance coefficient and the immersion depth on the propeller induced pulsating pressureIn order to consider the influence of non-uniform flow field on the propeller working beneath free surface,the SUBOFF submarine and the propeller 4381 are used as study objects.The numerical simulation of submarine-propeller system beneath the free surface was performed to analyze the influence of stern wake field of the submarine on the propeller.The three-way forces in coordinate system and flowing characteristics,such as,the vortex structure and velocity field were analyzed.