Time-Accurate Flow Simulations Past Helicopter Rotors in Hover and Forward Flight Conditions Using Chimera Grid Technique

Abstract

A study of time-accurate flow simulations past a two-bladed helicopter rotor was performed for hover and forward flight conditions, assuming inviscid compressible flow. The study was focused on the validation of the commercial CFD-FASTRAN solver for helicopter flow simulations using a moving Chimera grid technique. The flow field consisted of structured multi-block overlapped grids. For validation, the well-known wind tunnel model of the Caradonna and Tung two-blade rotor was considered. Two rotor flow configurations were studied. The first one concerned a lifting rotor in hover at two rotational speeds. The lower rotational speed produced a subsonic flow over the blades; however, the higher rotational speed induced a strong shock wave near the blade tips. The second configuration corresponded to a non-lifting rotor in forward flight in which a shock wave was present on the blade-tip region on the advancing side of the rotor. For the two rotor flow configurations, the numerical results showed that the locations of the shock waves were fairly well predicted and the pressure coefficient comparisons with the available CFD and experimental data showed very good agreement.