Simulating external flow using vortex method in two- and three dimensions

Vortex methods are numerical methods for simulating uid ow. They use a simple formulation where only the trajectories of discrete vortex particles are simulated. In our method we combine a high order particle-mesh based vortex method with an iterative penalization method to simulate external ows around arbitrary geometries such as bridge decks. The method only uses a discretized ge- ometry as input and can easily simulate an arbitrary motion of the geometry. As vorticity is a bounded quantity and the velocity eld can easily be calculated for a mixture of free-space- and periodic boundary conditions, the method allows for a minimized domain and hence minimal computational resources. However in an external ow problem, vorticity is produced in the boundary layers and transported downstream, consequently the computational domain must grow in time to encap- sulate the entire vorticity eld. We present a method for truncating this domain by supplementing the free-space- and periodic conditions with an out ow condition. The method is conveniently applied within the eld of bridge aerodynamics as it can be used for the calculation of the aerodynamic net forces, which depend highly on the geometry and the wake forming behind it. This is demonstrated in 2D and 3D simulations