Single- and Dual-Rotor Flowfield and Outwash Predictions

摘要

An empirical method and a computational fluid dynamicsrn(CFD) modeling of single- and dual-rotor outwash flowrncharacteristics are presented. The empirical approach isrnbased on the classical treatment of outwash flows forrnsingle and dual-rotor systems hovering in proximity tornground surface. But, whereas the classical method predictsrnoutwash only along orthogonal directions, forward and aftrnand outboard of the sides of the aircraft, the presentrnresearch generalizes the approach to outwashrndetermination at any azimuth. A numerical flowrncomputational method is also investigated for predictingrnthe complex In Ground Effect (IGE) flowfieldrnsurrounding dual rotor systems. This approach takesrnadvantage of some recent developments in Navier-Stokesrnflow solution scheme that involve efficient coupling of thernflow solver with a blade-element rotor analysis. Thernscheme substantially reduces computational time whilernpreserving reasonable accuracy, making it a feasiblernmethod for practical application to prediction of multirotorrnnear-field and outwash characteristics. Outwashrnpredictions for a single-rotor helicopter and a tiltrotorrnusing the empirical method and the CFD method arerncompared with predictions based on the current FederalrnAviation Administration (FAA) method. Correlation ofrnthe predictions from the empirical method with singlerotorrnhelicopter flight test measured data is also presented.