Unsteady incompressible turbulent boundary layer flow over a longitudinal cylinder

An analytical model is developed for unsteady turbulent boundary-layer flow over a cylinder in the presence of fluctuating and accelerating flow velocities. An eddy-viscosity treatment which allows for unsteady flow is used for the model, which accounts for the in- and out-of-phase velocity components. The governing partial differential equations with three independent variables are solved with an implicit finite difference scheme. Calculations made with the model are compared with experimental results for the differences between in- and out-of-phase flow velocities, the variation of the skin friction coefficient (SFC), the shape factor and Re over time and distance. Among other results, it was found that in laminar flows the SFC decreases with streamwise distance while Re increases at the same time with respect to the displacement and momentum thicknesses. In oscillating flows, the SFC and Re fluctuate over distance, and increase over distance in accelerating flows.