Characterization of Pulsed Vortex Generator Jets for Active Flow Control

Abstract : The flowfields produced by several active and passive flow control devices are being investigated experimentally and numerically as part of co-operative effort between the US Air Force Research Laboratory and the UK's Defense Evaluation & Research Agency (DERA). This manuscript reports the results of an experimental investigation of pulsed vortex generator jets (PVGJs) conducted at DERA's Boundary Layer Facility in Bedford. The focus of these tests was to investigate the influence of jet velocity, pulsing frequency, and duty cycle on the mean characteristics of the flowfield produced by a PVGJ in a turbulent boundary layer. The experiments were conducted in a zero-pressure- gradient flow at a freestream velocity of 32 m/s. The flowfield was explored using a three-component laser Doppler anemometry system, and the information is used to calculate local field properties such as velocity and velocity as well as global parameters like total circulation. The data give insight into the effectiveness of the VGs in terms of location. strength, and persistence of the generated vortices and their influence on the boundary layer. While the planned computational simulation effort is in its infancy, preliminary steady-jet computational results are compared with the flow field data that has been acquired in the boundary layer facility.