In this paper a method for the simulation of convection and diffusion of the vorticity, generated on a body surface is presented. A purely Lagrangian scheme is used for the vorticity convection, and thereby avoiding mesh associated problems. The body surface is simulated by straight-line panels, with constant-strength vortex distribution. The strength of the discrete vortices is obtained directly without going through any additional calculation. Using a primary diffusion process this vorticity is replaced by Lamb vortices located nearby the body surface. The diffusion process of the vorticity is simulated using the random walk scheme. Turbulence sub-grid scale modelling employs a Second Order Velocity Structure Function model adapted to the Lagrangian scheme. With a cloud of discrete vortices this velocity structure function model is employed to simulate the micro structures of the flow. The flow over a circular cylinder and a NACA 0012 aerofoil are considered to evaluate the integrated aerodynamic loads. Comparisons are made with previous theoretical and experimental studies.
Vortex method; panel method; turbulence model; sub-grid scale model
