Simulation of Rotor-Body Interactional Aerodynamics: A Time Accurate Rotor Model

The results in this paper are based on unsteady, compressible, viscous Navier Stokes formulations in body fitted computational grid coordinates which are implemented in the MPI version of the OVERFLOW_URS solver. A hybrid rotor source model consisting of time-averaged and time accurate models has been further developed within the architecture of OVERFLOW_URS in order to enable the interactional rotor/fuselage aerodynamics performance computation. The fully developed "unsteady" discrete rotor model is, however, considered to be a new approach for the analysis of rotor/fuselage complex interactional flows. Here, the rotor is represented by a distributed time dependent source model where their influences are imposed on the rotor blade platform only (i.e. no disk distributions). Hence the downwash effects of the individual blades can be assessed fairly accurately. In this the rotor effects are implemented in a similar fashion described in Ref: [1-4], by adding the force terms to the right-hand-side of momentum equations and a work-done term to the energy equation. The strength of these sources is then determined implicitly through the the rotor overall geometry and the aerodynamic characteristics of its airfoil sections. The rotor aerodynamic performance is computed in a fully coupled manner with the rest of the flow field solution within the computational domain. Consequently, the rotor wake is captured and not assumed. In order to enhance the rotor airloads computations, a rotor blade aero-elastic model is thus developed in conjunction with a new rotor dynamic trim model. This in turn has provided the capability of analyzing rigid and/or articulated rotor hinge models with the solver. In this, the discrete rotor blades are represented in a fashion similar to that employed in the classical lifting-line rotor model. Blade geometrical properties such as twist, chord, taper, and airfoil distributions are all accounted for in the model.