Underwater Navigation Body Airfoil Flow Noise Characteristics Study

The underwater navigational body hydrodynamic noise problem has been one of the important issues considered in the design and application of navigational bodies,because it directly affects the stealth and survivability of underwater navigational bodies.In order to study the hydrodynamic noise characteristics of underwater navigational body airfoil parts and improve the acoustic stealth of underwater navigational body,this thesis takes the typical NACA airfoil as the main research object and conducts a detailed study of airfoil flow noise and flow excitation noise on the basis of accurate verification of numerical simulation.Firstly,the accuracy of the numerical simulation method is verified by using SUBOFF submarine model,the RNG turbulence model is used for constant calculation,and the large eddy simulation is used for non-constant calculation.On this basis,two series of six leading edge filling angle schemes are designed.By studying the effect of leading edge filling angle on flow noise,the airfoil profile design is proposed to reduce flow noise,and it is found that the airfoil flow noise reduction effect is better when the leading edge filling angle is curved,among which the noise reduction effect is optimal when the curvature of leading edge filling angle is 10 cm,reaching 5.1 d B.Secondly,this thesis also conducts a study on solving the airfoil flow noise using the boundary element method and compares the results with the FW-H equation method.It is found that the results of the two methods are very close in the near field and the results of the FW-H equation are large in the far field,and the FW-H is more suitable for solving the information in the far field due to the processing method using tight sound sources.Then,in view of the flow noise in the hydrodynamic noise occupies a non-negligible position,this thesis also carried out the use of structural discrete method of airfoil flow noise characteristics of the study,found that the structural discrete method and the experimental test results within 3 d B difference,airfoil flow noise on the airfoil shape change is not obvious,compared to the airfoil shell thickness on the flow noise is more significant,shell thickness of every 3mm,airfoil flow noise decreased by about 3 d B.Finally,for the typical airfoil convex body of underwater vehicle,this thesis carried out an acoustic wind tunnel test on the characteristics of the flow exciting force on the surface of the airfoil,and summarized the distribution characteristics of the flow exciting force on the surface of each part of the airfoil structure.Based on the experimental results,a new method for correcting the turning point of the wing surface was proposed.After the correction,the deviation between the calculated value and the experimental value was less than 10%,which provides an experimental analysis method for the research on the flow excitation force of underwater vehicles.