Simulation Of Cavity Flow Based On LES Method In High Reynolds Number

The fluid flowing through the cavity may produce the pulse of pressure, velocity and can produce noise.In recent years, many researchers did the research of the cavity mostly based on the low Reynolds number, low Mach number or in air flow field.In respect of high Reynolds number of water flow field research, few studies and scholars both inland and abroad set their feet in.In this paper I mainly do the research of cavity at high Reynolds number in water field to get the turbulence characteristics and the flow characteristics.The shape of the cavity may influence the characteristics,so I add the shape influence of the cavity in the final chapter.First chapter is the introduction of the whole paper.In this chapter I briefly introduces several methods of numerical simulation to solve turbulence, and compares the pros and cons of different numerical simulation method, then introduces the history and evolution of the cavity flow, finally briefly introduces the main work of this article.In the second chapter, from the basic idea of large eddy simulation, numerical calculation method of large eddy simulation was introduced in detail: First use the filter function to separate large scale pulse and small scale fluctuation in the turbulence field, and separate the small scale fluctuation through filtering function; Then build the sub-grid Reynolds stress model and calculate the sub-grid Reynolds stress to make the control of the large eddy simulation equations closed.The third chapter presents the theoretical basis for the analysis of cavity noise and foundation: In the introduction of theoretical basis,Lighithill first put forward the equivalent source method to deal with the noise module;Then considering stationary boundary effect thus Curle equation was derived by Curle.Ffowcs-Williams and Hawkings introduced Heaviside function H(f) and its derivative Dirac function ?(f), theintegral control method was put forward and the implementation process of integral control surface method in was introduced in detail.Finally the Fourier transform method to deal with the discrete noise data was introduced in detail.On the basis of theoretical analysis,the fourth chapter of this paper is to calculate the cavity by a detailed numerical validation on the analysis of the Reynolds number.In this chapter,a two-dimensional cavity is studied under different Reynolds number to get the resistance,flow characteristic,and wake flow patterns and other features.As the mesh density, the time step will affect the result, this chapter adds the grid independence and the time step validation in order to increase the reliability of numerical calculation.Considering the shape of the cavity may influence the noise characteristics, we design the “Area Reynolds Number”, the cavity is studied under the same area conditions and different working conditions to get the the characteristics of flow and noise.This chapter is divided into three parts: At first cavity is studied in the same area but different long depth ratio and then the cavity is studied under different rake Angle,finally on the inside of the cavity baffle effect of cavity was further studied.