Influence of the L/D ratio on the rotary coefficients of a submarine

Abstract

AbstractAt the early design stage of a submarine, it is necessary to have a good estimate of the linear manoeuvring coefficients, or derivatives. These are necessary to determine the required size of any appendages to achieve the desired level of motion stability and controllability. Various empirical methods exist to make such estimates, including the influence of appendages. However, methods do not exist to predict the linear rotary coefficients (i.e. $${Y}_{r}^{^{\prime}}$$ Y r ′ and $${N}_{r}^{^{\prime}}$$ N r ′ ) for a bare hull. Thus, the aim of this work was to determine the values of the linear rotary coefficients for an axisymmetric underwater body as functions of Length to Diameter (L/D) ratio to improve the empirical estimate of these values for a fully appended submarine. The work was performed using validated Reynolds Averaged Navier Stokes (RANS) based simulations to obtain forces and moments on the body. It is considered that the developed expressions for the linear rotary coefficients are adequate for an unappended axisymmetric underwater body at the design stage over the range: 6 ≤ L/D ≤ 14, which can then be used to size and locate the appendages.