Towards the Detection of Low-Observable Flying Object in the Presence of Wake Vortex Flow

It is well-known that one of the parameters useful to detect low-observable stealth targets, specifically aircraft, is to monitor the Radar Cross Section (RCS) enhancement in the medium surrounding the aircraft due to the wake vortex generated during the flight. The acoustic wave induced by the wake vortex creates dielectric constant fluctuations because of compressions and rarefactions in the propagating medium. The subject matter of this work is to develop a method to rigorously predict RCS in the presence of wake vortex. First, the solution of flow over an aircraft is obtained, then permittivity of the medium is computed using flow parameters, providing the coupling term between the electromagnetic and acoustic phenomenon. Then Electromagnetic (EM) scattering from the inhomogeneity due to the flow in the vicinity of the aircraft and in its wake region is computed for an incident plane wave in lateral and longitudinal directions. The scattering problem is solved using Integral Equation (IE). The scattered far-field is interpreted using the conventional radar equation and the enhancement in RCS and detectability are presented. It is believed that this is the first time that an IE method is used to study the EM scattering problem from an aerodynamic flow and its detectability. It is shown in this paper that the presence of wake vortex can enhance the detectable range by around 2 km at 250 MHz giving an early warning advantage of around 15 seconds.