Boundary-layer control using “Deterministic Turbulence”

The aim of this experimental study is to develop and optimise the control strategy to reduce the skin-friction drag of turbulent boundary layers. This will be tested on a pseudo-randomly excited boundary-layer during the late stage of transition, where the velocity fluctuations (therefore the flow structures) are repeatable even when the turbulence statistics becomes very similar to that of a fully developed turbulent flow. Sensors are not required for the boundary-layer control with “deterministic turbulence” since the large turbulence structures are repeated each time the experiment is run using the same excitation signal. Experiments were carried out in a very low-turbulence (less than 0.01%) wind tunnel, where the laminar boundary layer over a flat plate was excited by broadband noise. Therefore, the receptivity of the boundary layer to the background noise is much weaker than that to the initial excitation with broadband noise. The turbulence structures such as the Λ-vortices and the turbulent spots were repeatably realised in the “deterministic turbulence”. Control will be through suction/blowing and plasma actuators.