A Novel Test Bed for the Aeroacoustic Investigation of UCAV Configurations with Highly Integrated Propulsion Systems

In this contribution, a novel test bed designed for the experimental investigation of the acoustic signature of unmanned combat air vehicle with highly integrated propulsion systems is presented. The model integrates a curved intake duct design as well as a curved, high aspect ratio, rectangular nozzle design. Operation of the model in suction mode or pressurized mode allow investigations of the intake and nozzle acoustics independently and in a realistic Mach number range, e.g. Ma=0.4 in the intake duct and Ma=0.75 in the jet. Intake sound emissions are found to have a directivity peaking in the forward arc which is strongly dependent on the suction mass flow rate and almost independent of the free-stream Mach number. The jet is found to radiate sound with a rear arc directivity for model scale frequencies above 3.15 kHz. The acoustic is also a strong function of the nozzle mass flow rate only. The overall shape of the jet acoustic directivity suggests the existence of two source component aligned at 90° and 140° to the upstream direction, respectively