A Statistical Turbulence Model for Shipboard Rotorcraft Simulations

This paper describes an efficient statistical ship turbulence model based on the von Karman spectral density functions. The statistical turbulence model is capable of modeling the full-field ship turbulence in a rotorcraft/ship interactive simulation environment. The computational efficiency of this model was achieved by using a set of frequency grids for equal-energy subdivisions. With a polar coordinate transformation, the frequency grids were determined by analytically solving the integral equations for the turbulence intensity. With these discrete frequencies, the turbulence velocity time histories can be generated using a sum of cosine functions with phase randomization. The statistical turbulence model was implemented and integrated into the FLIGHTLAB rotorcraft/ship dynamic simulation program. The simulation results indicated that the new model was able to recover the turbulence energy over the frequency range of interest. This paper presents the validation of the turbulence model by comparing the ship airwake variations reconstructed from the turbulence model against the at-sea measured test data as well as the unsteady CFD results. It also shows the application of this model to the simulation of the H-60 class helicopter shipboard operations.