Analyzing the vortex dynamics in bluff-body wakes by Helmholtz decomposition of the velocity field

The velocity field in the wake of a bluff body is calculated by a novel procedure for the Navier-Stokes equations in the vorticity-velocity formulation. The time evolution of the vorticity is solved as an ODE problem on each node of the spatial discretization, using at each step of the time discretization the spatial solution for the velocity field provided by a new PDE expression called the kinematic Laplacian equation (KLE). Then, the Helmholtz decomposition is applied to the velocity field to study the topology of the flow. The observation of the decomposed field provides new insights into the physical processes of vortex formation and shedding, and their connection with the subsequent rearrangement of the vortices into an eddy-street wake. Results for a circular cylinder are presented, discussed and compared with experimental results for validation.