A SPATIAL MODEL OF WIND SHEAR AND TURBULENCE FOR FLIGHT SIMULATION (MONTE CARLO, SIMULATION, MICROBURST)

A three dimensional model which combines measurements of wind shear in the real atmosphere with three-dimensional Monte Carlo simulated turbulence was developed. The measurement of three-dimensional wind shear is a recent development. Measurements were made on a rather coarse ((TURN) 200 m) grid scale so that high frequency, short length scale turbulence information was not included. Some of the missing frequencies are important to aircraft response and hence for flight simulation. The missing turbulence must be added to the wind shear measurements. The spatial model adds three-dimensional, Monte-Carlo simulated turbulence conforming to the von Karman model. The turbulence was generated in the frequency domain and transformed to the space domain using Fast Fourier Transform techniques. The resulting turbulence is three-dimensional and contains lateral and vertical as well as longitudinal correlations associated with isotropic turbulence. The resulting Gaussian, isotropic turbulence is multiplied by a spatially varying gust intensity and added to the wind shear data set winds. The resulting simulated wind field is nonisotropic, non-Gaussian, and nonlinear as are winds in the real atmosphere. Previous turbulence simulations were either one-dimensional or accounted for two- or three-dimensionality in an artificial way. With the present model, the wind field over the body of an aircraft can be simulated and all aerodynamic loads and moments calculated. The inclusion of three-dimensional variation of winds and turbulence is believed to be a significant advance over previous wind simulation models.