Thermal Power and Fluid Engineering
Example dissertation project
The Sensitivity of Synthetic Jets to Initial Conditions.
Supervisor Dr M A Cotton
Synthetic, or ‘massless’, jets are active flow control devices currently under investigation with a view to possible application in the manipulation of boundary layers over the flight surfaces of commercial aircraft. Air is alternately ejected and ingested from the orifice of a small cavity, the flow being produced by the motion of a diaphragm located at the base of the cavity. Because of the thinness of the boundary layer, interest is centred primarily on the very-near-field of the jet (up to around 5 orifice diameters for a round jet, or 5 slot widths for a plane 2D jet) and therefore the turbulence ‘memory’ of its initial conditions at the exit plane is of far greater importance than in jets where attention is focused on the far-field.
A recently-completed PhD project used the in-house computer program ‘STREAM’ to examine synthetic jets in quiescent environments using the standard k-ε turbulence model and a variant two-timescale model that furthermore places particular emphasis on the action of normal straining and rotational motion in the energy transfer and dissipation processes. It is intended that the present project will continue this work by carefully examining the sensitivity of downstream flow development to the detailed specification of mean flow and turbulence profiles at the exit plane.