Study on the Hydrodynamic Coefficients of a Submarine in the Density Stratified Flow

Abstract

Due to the difference in temperature and salinity, density stratification exist in the actual ocean environment. Under this situation, any disturbance may excite internal waves. In the density stratified flow, the safe operation of a submarine will be influenced by internal waves. In recent years, more and more researchers had paid attention to this issue. This paper takes the SUBOFF submarine model as the research object. The Computational Fluid Dynamics (CFD) method is used to investigate the flow field and the hydrodynamic coefficients of the submarine. Reynolds Average Navier-Stokes (RANS) method is used to simulate the wake fields of submarine traveling in the stratified fluids. The volume of fluid (VOF) method is used to capture the body-generated internal wave. Uncertainty analysis of grid size and time step are carried out to obtain the convergent results. The effects of the distances from the internal interfaces and density of stratified fluid on the wave pattern of SUBOFF are investigated in detail. The hydrodynamic coefficients of the submarine were obtained through the plane motion mechanism (PMM) in virtual tank taking the effect of density stratification into consideration. Forced motion of SUBOFF is numerically simulated by combining DFBI method and overset grid technology. By comparing the hydrodynamic coefficients of the submarine under different densities and depths, the hydrodynamic characteristics of the submarine in density stratified flow are discussed.