Three dimensional numerical simulation of rotor in vertical descent flight

Using the actuator disc model, blade element momentum theory and computational fluid dynamics (CFD)method, the flow field and aerodynamic performance of a helicopter rotor in vertical descent flight were simulated. In calculation, the loads of spinning rotor were represented as momentum source terms distributed along the span of the rotor with functional relationship to the local flow conditions. The finite volume method was adopted and incompressible Navier-Stokes (N-S) equation was solved in Cartesian coordinates. The Spalart-Allmaras (S-A) turbulence model, especially the induced velocity empirical formulae were also included in the calculation method. The simulation results for flow field and aerodynamic performance show good agreement with the experiment data. Therefore, this numerical simulation technique is proved to be feasible for analyzing rotor flow characters in descent condition and it also provides the references for the further vortex ring state research.