Free flying models in hypersonic facilities
(Prakash, Mudford, O’Byrne, Choudhury, Neely)
Wind tunnel models are typically held in place by a mounting mechanism to ensure that they do not move while the flow of air passes over them. While this is convenient in many situations, there are some interesting flow problems where the mounting of the model can interfere with modelling what would really be happening to the model in flight. One problem involves the flow at the rear of the model, known as the wake flow and the other involves the response of the vehicle to changes in the surrounding flow. The first problem is particularly important for correctly modelling the flow around atmospheric entry vehicles, while the second is critical to understanding how to control the hypersonic vehicle in flight. Our research group has approached these problems by allowing the models to fly unsuspended during tests in our T-ADFA hypersonic facility and in the University of Southern Queensland’s TUSQ facility. In order to account for the motion of the model in the tests, we have used high-speed imaging and advanced image-processing techniques to track the position, angle of attack and acceleration history of the model during the hypersonic test. Tests of model deployment systems and image acquisition experiments have been successfully performed in both facilities. Because the model is no longer tethered to the facility, all data acquisition must be performed on the model itself using an embedded microcontroller integrated into the model. Such self-contained data acquisition systems have been developed in 2010 to measure surface heat flux, acceleration and pitch/roll rates.