[Seminar] "An Immersed Boundary Method for high-fidelity simulations with moving objects: application to active flow control" by Dr. Athanasios E. Giannenas

Speaker

Dr. Athanasios E. Giannenas - Imperial College London

Title

An Immersed Boundary Method for high-fidelity simulations with moving objects: application to active flow control

Abstract

Performing simulations of moving objects with complex geometries on supercomputers remains a considerable challenge in the field of computational fluid dynamics. As body-conforming methods are costly (due to re-meshing) and suffer from mesh-related issues, non-body-conforming Immersed Boundary Methods (IBMs), which eliminate re-meshing have emerged. Here, a simple and scalable Alternating Direction Reconstruction IBM is proposed for high-fidelity simulations with multiple and relatively complex moving geometries in laminar and turbulent flows on High Performance Computing (HPC) facilities. The method imposes the boundary conditions at the walls via 1D cubic spline interpolations and is combined with high-order finite-difference schemes. The accuracy of the method is highlighted via laminar and turbulent simulations involving both fixed and moving geometries. Further, the method is used for the active flow control study of the interacting flow dynamics of a bluff body wake generated by a rectangular bluff body with a pair of rear pitching flaps at low Reynolds numbers (80 ≤ Re ≤ 200). The harmonic in-phase and out-of-phase pitching flap motions alter the mean and unsteady hydrodynamic forces thanks to a fundamental or a subharmonic resonance and a partial or complete wake symmetrisation. Finally, a single scaling parameter is proposed for the prediction of the mean drag reduction while the efficiency of the pitching motions is assessed to identify the optimum net-energy-saving drag reduction strategy.

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