Confirmation of Candidature - Candidate : Alister Webb

Hypersonic boundary layer transition is an increasingly important area as transitional and turbulent boundary layers in this regime can lead to significantly increased thermal and structural loading compared to laminar boundary layers. Heat flux and friction coefficient can increase from laminar to turbulent flow by up to two orders of magnitude. For hypersonic flight applications, higher thermal loading from this increased heat flux creates unfavourable conditions. Thermal Protection Systems (TPS) can be used to mitigate against these effects; however, these increase the weight of the vehicle - thus decreasing its efficiency. In some cases, turbulence can induce early boundary layer separation which can lead to limited or reduced control authority. For these reasons there is much interest in laminar-turbulent transition, and methods that can be employed to control this process.
A large amount of both experimental and numerical work currently exists on the effect of wall temperature on boundary layer transition - specifically on what is called the second mode instability. However, there have been no attempts to date at utilising this effect to control a transitional boundary layer.
The purpose of this project is to develop a method of spatial boundary layer transition control. The method is expected to utilise heating/cooling of a localised portion of an experimental model to stabilise/destabilise the second mode instability. Simply put, this boundary layer instability is receptive to wall temperature, and so should be able to be used to control boundary layer transition by stabilising or destabilising it with defined surface temperatures.
Experimental work will be conducted in TUSQ at the University of Southern Queensland, Toowoomba campus. This work will involve design and implementation of a method of local surface temperature control on a 7-degree half angle cone model. The model will be instrumented such that pressure fluctuations (and optionally, heat flux) on the surface of the model can be obtained. From this, the temporal and spatial growth rates of the second mode can be found and used to determine the efficacy of the control method.

For more information, please email the Graduate Research School or phone 0746 31 1088.