Numerical Simulation of Wake Vortex Detection Using a Radio Acoustic Sounding System

A parallel, two-dimensional Euler, one-dimensional Maxwell code is developed to numerically simulate wake vortex detection using a radio acoustic sounding system. The code is written in Fortran 90 with the message passing interface for parallel implementation. The main dife culty with a time-accurate simulation is the number ofsamplesrequired to resolve theDopplershiftin thescattered electromagneticsignal. Even fora one-dimensional simulation with typical scatterer size, the CPU time required to run the code is far beyond currently available computer resources. Two alternatives that overcome this problem are described. In the e rst, the code is run for a e ctitious speed of light. Second, the governing differential equations are recast in order to remove the carrier frequency and solve only for the frequency shift using an implicit scheme with large time steps. The numerical stability characteristics of the resulting discretized equation with complex coefe cients are shown. The code is run for both the approaches with Taylor and Oseen vortex velocity proe les. Finally, the Abel transform is applied to the outputs of both explicit and implicit schemes, and the wake vortex velocity e eld is retrieved with very good accuracy.