Two-dimensional simulations of wake vortex detection using radio acoustic sounding systems

A parallel code is developed to simulate numerically wake vortex detection using a radio acoustic sounding system (RASS). The code is written in FORTRAN 90 with the message passing interface for parallel implementation. The numerical simulation solves simultaneously the linearized Euler equations for a nonuniform mean flow and the Maxwell equations for a nonhomogeneous medium. The radar transmitter and receiver antennas are modeled using an array of point sources and a beam-forming technique, respectively. Many features of the RASS are explored using the numerical simulation. First, a uniform mean flow is considered, and the RASS simulation is performed for two different types of incident acoustic field: a short single-frequency acoustic pulse and a continuous broadband acoustic source. Both monostatic and bistatic configurations are examined, and their results are compared. Taylor and Oseen vortex velocity profiles are used as sample models, and their mean flowfields are reconstructed from the backscattered electromagnetic signal using the Abel transform. The effect of radar beam width is also considered, as are the issues of nonaxisymmetric and interacting vortices.