Simulation of normal vortex-cylinder interaction in a viscous fluid (Q2710584)

The authors study numerically the secondary vorticity field generated by a solid cylinder during the interaction with a normal vortex filament. The computational method solves Navier-Stokes equations for incompressible fluid with uniform density in vorticity-velocity form on a set of Lagrangian computational points, using a tetrahedral velocity element method in conjunction with a filament approximation for the primary vortex. A tetrahedral mesh is refitted to computational points at each time step using a fast three-dimensional Delaunay triangularization. The boundary condition for vorticity at the body surface is specified by balancing vorticity associated with surface slip with total vorticity transported into the fluid volume during the timestep. NEWLINENEWLINENEWLINEThe results of simulations are reported for vortex Reynolds numbers of 500 and 1500. Both for the case of no free-stream velocity and for the case with free-stream velocity oriented tangentially to the cylinder axis, the secondary vorticity is observed to form a loop-like structure that ejects outward from the cylinder surface and wraps around the primary vortex. When a free-stream velocity is introduced normally to the cylinder axis, the secondary vorticity does not develop into a loop-like structure, but instead rolls up to form a vortex that is located just off the cylinder surface, with vorticity oriented mostly in the azimuthal direction.