Modeling of boundary layer growth on long cylinders

Flow induced noise is a significant source of noise in towed array sonars. In order to determine the level and characteristics of the noise a good description of the turbulent pressure fluctuations on the sonar surface is needed. Semi empirical models offers an effective way to describe these pressure fluctuations, which takes boundary layer variabels as input. In order to estimate the boundary layer properties with an effective method, boundary layer growth along long cylinders in axial flow are investigated. Scaling effects of the boundary layer growth with freestream velocity, cylinder radius, Reynolds number and downstream position are investigated. The results from fluid mechanics simulations are evaluated against data from the literature, which indicates that the simulation methodology performs satisfactory. Modified semi-empirical models for the friction coefficient, boundary layer thickness and deplacement thickness are presented. These models for the boundary layer variabels can be used to estimate the parameters in semi empirical models used to describe the turbulent pressure fluctuations on the cylinder surface.