Modelling,parameterisation and simulation-based optimisation of a microflow-control actuator

A synthetic jet is considered to control microflows, where the Knudsen number is between 0.001 and 0.1. The flow is modelled with the compressible, 2D Navier–Stokes equations. The wall boundary conditions are modified for the slip velocity and the temperature jump encountered for this Knudsen number range. The membrane motion is modelled as a moving boundary. After a validation using experimental results available only for a macroflow over a hump, the present study focuses on developing a design optimisation methodology for micro-synthetic jets in micro-scale, laminar crossflow. First, single-variable optimisations are performed. As compared to the baseline case, the optimisations yield 2, 15, 15 and 200% increase in actuation efficiency for the cases varying the orifice width, the orifice height, the cavity height and the frequency, respectively. Then, multi-variable shape optimisation is performed. Compared to the baseline case, the optimisation using shape parameters results in a 7-fold increase in the actuation efficiency, while the optimisation with Bezier polynomials results in more than a 10-fold increase.