Reduced order modelling and optimization of an electromagnetically controlled shear layer


Reduced order modelling and optimization of an electromagnetically controlled shear layer

Metzkes, H.; Stiller, J.; Weier, T.; Albrecht, T.; Gerbeth, G.

In previous work it has been found that active flow control on a separated shear layer of an airfoil is able to increase lift by 50 percent. It was shown, the effect of control depends on various parameter like amplitude, frequency waveform of the signal. The electromagnetic actuator we use, induces a mainly wall normal body force. As the force amplitude is proportional to the external applied voltage a wide range of time signals can be generated.
Due to the variety of actuating variables present work was focused to study the variation of unique parameters. Our aim is to set up an optimization method including a wide range of variables to find the most effective constellation. In order to reduce the numeric costs for the optimization we use a reduced order model. The model is derived by projecting the Navier-Stokes equation to a basis derived from proper orthogonal decomposition (POD). The POD modes are computed from autocorrelated snapshots of a high fidelity solution (Direct Numerical Simulation or Large Eddy Simulation). To cope with pressure effects due to open boundaries we adopted the approach of Noack et al. (2005). The choice of the snapshots restricts the area of application of the model. For this reason the optimization has to be combined with a trust region method . As there are several references dealing with cylinder wake flow, we validate the approach with the flow past a circular cylinder with Re = 100. In order to work out a suitable strategy for controling separated shear flows we consider the backward-facing step as a simple, but yet characteristic example. As a particular challenge we plan to address the reduced order representation of short forcing peaks and a robust selection of snapshots within the trust region iteration of the optimizer.

Keywords: backward facing step; Lorentz force; flow control

  • Lecture (Conference)
    European Fluid Mechanics Conference 9 (EFMC9), 09.-13.09.2012, Rom, Italien

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Publ.-Id: 17369