Simulation of unsteady three-dimensional viscous compressible propeller flow by finite element method

The flow produced by a rotating propeller is inherently unsteady and three-dimensional. Conventional design of propellers uses blade-element theory but becomes inaccurate in capturing three-dimensional vortical and compressible effects at the tips, as well as the effect on downstream bodies. A propeller is always attached to a fixed component that affects its performance, thus the need arises to couple a fixed domain to a rotating domain in an unsteady aerodynamic simulation. A finite element formulation for the simulation of propellers is presented in terms of the Reynolds-averaged Navier-Stokes equations for unsteady, three-dimensional, viscous, compressible flows. The first step consists of preparing a mesh containing two separate domains interfacing at a virtual surface. Then, simulation is run to obtain an initial solution. This step highlights the live/dead interfacing scheme between the fixed and rotating domains without mesh movement. Finally the unsteady simulation performs interpolations at each time step with node movement until a periodic steady state is reached. Mesh movement can be treated by either an ALE formulation or a rotating frame of reference correction. Two test cases are used to validate the code: a two-dimensional pitching airfoil in transonic flow and a 3-bladed 5868-9 propeller with a liquid cooled nacelle.