Fluid Structure Interaction Simulation And Hydrodynamic Noise Prediction Of The System-wide Underwater Vehicle

The acoustic stealth is of paramount importance to the underwater vehicle.In order to study the hydrodynamic noise of underwater vehicle,the numerical simulation method is employed in this paper to conduct research on the flow field around the underwater vehicle,propeller excitation force,hydrodynamic noise and the fluid-structure interaction of the rudder.First,the article studies the flow field around the underwater vehicle by the RANS turbulence model for the unsteady flow field is the primary cause of hydrodynamic noise.Also the effects of the appendage position and Reynolds number on the flow field the evolution of flow field around the underwater vehicles are analyzed.It turns out that the influence of the wing on the propeller disk flow field is much greater than that of the sail and Reynolds number.As the wing approaches the propeller disk,the unevenness increases while the turbulence intensity decreases slightly.Furthermore,there is a critical distance between the sail and the propeller disk.When the distance is less than the critical distance,the speed distribution on the propeller disk changes significantly.Second,the flow field around the SUBOFF model fitted with the INSEAN E1619 propeller at the self-propulsion point was separately simulated by the RANS and DES turbulence models.Specifically,the relationship between the propeller excitation force and the flow field is analyzed.The difference between the propeller excitation force predicted by different numerical models in the time domain and frequency domain is compared.Also,the RANS model's ability of predicting the excitation force is evaluated.The results show that the blade load pulsation predicted by the DES model is significantly larger than that of the RANS method,however,the force remains the same by these two different models after the phaseaveraged evolution process.Third,the hydrodynamic noise of underwater vehicle is predicted with resorting to the combination of the result of flow field and FWH sound analogy equation.The contribution of propeller to hydrodynamic noise and its influence on the directivity of hydrodynamic noise are analyzed.The results indicate that the disturbance brought by the propeller can significantly increase the level of hydrodynamic noise and the increase is more obvious with longer distance.Last,a separate,strongly coupled fluid-structure coupling algorithm for the threedimensional elastic hydrofoil is established resorting to CFD software STARCCM + and the FEM structural finite element software ABAQUS.Using this algorithm,the hydrodynamic performance and structural response of the NACA 66 flexible hydrofoil at different angles of attack are investigated.It is found that the hydrofoil undergoes large bending deformation under the hydrodynamic load,at the same time,it has a certain degree of torsional deformation.Moreover,the torsional angle gradually increases with the initial angle of attack,which slightly increases the lift coefficient.In addition,under the action of hydrodynamic load,the first-order wet mode of the hydrofoil is excited,in which the frequency does not change with the angle of attack.