Helicopter Turbulence Modeling for Flight Simulation and Handling-Quality Analysis

This paper presents a distributed turbulence model with accurate spatial correlations for helicopter flight simulation and handling-quality analysis. Firstly, digital filters with longitudinal correlations of the von Karman turbulence are developed to generate discrete turbulence velocity components. Meanwhile, turbulence transverse correlations are considered by relating the filters in different positions with spatial correlations of the von Karman theory. Then, the distributions of both the related filters on the transverse plane in front of helicopter and their velocity components in the longitudinal direction of airspeed, as well as turbulence models of helicopter aerodynamic surfaces are established. Finally, a flight dynamics model coupled with the turbulence model is developed and validated against the flight test data. The effect of turbulence transverse correlations on helicopter handling qualities is analyzed. The results show that neglect of turbulence transverse correlations would aggravate the "rotor-to-body attenuation" effect of main rotor, which results in the underestimate of helicopter roll, pitch and heave rate responses to atmospheric turbulence in the interested frequency range of handling qualities but there is nearly no effect on yaw rate response.