A METHODOLOGY FOR THE ANALYSES OF UNSTEADY FLOWFIELDS AROUND FORWARD FLYING HELICOPTER ROTORS

This study presents the outcomes of a series of computational fluid dynamics analyses conducted to obtain unsteady solutions of the flowfields around single rotor helicopter configurations. We use a methodology to obtain the time dependent solutions of the 3D, compressible Navier Stokes equations adapted for a rotating frame of reference. In order to carry out the simulations, the developed mathematical model is solved on hybrid meshes to optimally benefit the advantages of both the structured and the unstructured grids. For the entire flowfield calculations, one-equation Spalart-Allmaras turbulence model is employed. To decrease the computational time and memory requirements, parallel processing with distributed memory is utilized. We validate the developed model and the simulation methodology by comparing the results with the published experimental data. In the following phase of the study, the unsteady calculations of the flowfields around single, two bladed helicopter rotor configurations are conducted for hover and forward flight cases. As the forward flight speed increases, development of the dissymmetry of lift on advancing and retreating blades has been observed for six advance ratios. These time–accurate computations help to analyze the adverse effect of increasing forward flight speed in order especially to determine the never-exceed speed for single rotor helicopter configurations