NUMERICAL SIMULATION OF ROTARY WING FLOWFIELDS
ON PARALLEL COMPUTERS
by
Alpman, Emre
M.S., Department of Aeronautical Engineering
Supervisor: Assoc.Prof.Dr. Yusuf Özyörük

      In this work, a computer code, is developed to compute the flowfields of fixed and rotary wing configurations for two and three-dimensional cases. The code solves unsteady thin-layer Navier-Stokes and Euler equations and employs finite volume discretization with the compact, four step, Runge-Kutta type time integration technique. H, C, C-O, and H-H type structured grids are employed in the solutions. Parallel processing with distributed memory is utilized to reduce computational time and memory requirements. The data communication among the processors is performed using the MPI (Message Passing Interface) communication libraries. Calculations are done for subsonic inviscid flow over the NACA 0012 airfoil, inviscid transonic flows over the RAE 2822 airfoil and the root section of the Onera M6 wing, inviscid and viscous laminar transonic flows over the Onera M6 wing, and inviscid subsonic and transonic flows over a two bladed UH-1 helicopter rotor. In the rotary wing cases, non-lifting and lifting rotor solutions are obtained separately and the blade vortex interaction phenomenon is investigated. For the fixed wing problem, multigrid convergence acceleration is employed along with single grid solutions. The results are, in general, in good agreement with experiments. The applied multigrid technique successfully increases the convergence rate, but is sensitive to mesh non-uniformities. In the rotary wing case, the vortical wake experiences a rapid and unphysical dissipation due to numerical algorithm, which can be overcome by high-order formulations and substantial grid refinement.

Keywords : Rotary wing, thin-layer Navier-Stokes and Euler equations, finite volume method, structured grid, parallel processing, MPI, blade vortex interactions, multigrid convergence acceleration technique

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