Numerical simulation of aerofoil and bluff body flows by vortex dynamics
The computer simulation of flow separation from bluff bodies is achieved by a method which solves the two dimensional incompressible Navier-Stokes equations using clouds of point vortices. The vortices convect each other, and have an additional random motion to represent viscosity, as originally proposed by A. J. Chorin. Some justifications for the introduction of randomness as the agent of entropy production are presented. The method is applied to some simple boundary layer simulations, and then in combination with an integral equation method due to E. Martensen , the flow around bluff bodies of arbitrary shape is simulated in order to predict lift and drag. The stalling characteristics of aerofoil NACA 0012 are reproduced from first principles by computer simulation, and the results compared to experiment. The dependency of the Strouhal number against Reynolds number for the von Karman vortex street behind a circular cylinder is also investigated by simulation. An attempt is made to simulate the phenomenon of rotating stall which appears in curpressors as the first sign of aerodynamic overloading.