Simulation of a large-eddy-break-up device (LEBU) in a moderate Reynolds number turbulent boundary layer

SESSION 1A - Drag Reduction I. 1A-3A well-resolved large eddy simulation (LES) of a large-eddy break-up (LEBU) device in a spatially evolving turbulent boundary layer up to Req ≈ 4300 is performed. The LEBU is a flat plate that is implemented via an immersed boundary method. Initial flow visualizations show successful implementation of the LEBU. The LEBU is located at a wall-normal distance of 0.8d (local boundary layer thickness) from the wall and acts to delay the growth of the turbulent boundary layer. The LEBU serves to reduce skin friction drag up to 160d downstream of the LEBU but no net drag reduction is found. Investigation is performed on the interactions of high and low momentum bulges with the LEBU and the corresponding output is analysed, showing a ‘break-up’ of these large momentum bulges. In addition, results show an attenuated turbulence intensity profile downstream of the LEBU, which is mainly due to a reduction in energy at spanwise length scales of l + z 500.Cheng Chin, Jason Monty, Nicholas Hutchins, Andrew Ooi, Ramis Örlü, Philipp Schlatte