Distributed turbulence model with accurate spatia correlations for helicopter handling-quality analysis

Abstract

This paper presents a distributed turbulence model with the von Karman correlations for helicopter flight simulation and handling-quality analysis. First, turbulence filters based on the longitudinal correlations of the von Karman model are discretized by a high-precision transform method. Turbulence transverse correlations are considered by relating the discrete filters in different positions with spatial correlations of the von Karman model. The distributions of both the related filters on a transverse plane and their velocity components along the longitudinal direction of airspeed are established to form a distributed turbulence model. Then, the turbulence model is integrated into a flight dynamics model and validated against the flight test data. Finally, the effects of both the turbulence filters and turbulence transverse correlations on helicopter handling qualities are discussed. The results show that the Nyquist frequency of sampling period for helicopter flight simulation in atmospheric turbulence should be larger than three times of the interested frequency. The turbulence filters based on the longitudinal correlations of the von Karman model improves the accuracy of helicopter handing-quality analysis in the higher frequency range for the flight conditions with low airspeed and high altitude. The transverse correlations improves the accuracy of helicopter handling-quality analysis in the lower frequency range