Modelling and feedback control of vortex shedding for drag reduction of a turbulent bluff body wake

Abstract

Three-dimensional bluff body wakes are of key importance due to their relevance to the automotive industry. Such wakes have both large pressure drag and a number of coherent flow structures associated with them. Depending on the geometry, these structures may include both a bistability resulting from a spatial symmetry breaking (SB), and a quasi-periodic vortex shedding. The authors have recently shown that the bistability may be modelled by a Langevin equation and that this model enables the design of a feedback control strategy that efficiently reduces the drag through suppression of asymmetry. In this work the stochastic modelling approach is extended to the vortex shedding, capturing qualitatively both the forced and unforced behaviour. A control strategy is then presented that makes use of the frequency response of the wake, and aims to reduce the measured fluctuations associated with the vortex shedding. The strategy proves to be effective at suppressing fluctuations within specific frequency ranges but, due to amplification of disturbances at other frequencies, is unable to give drag reduction.

Experimental analysis of the effect of local base blowing on three-dimensional wake modes

“…In addition to jet actuation, there have been several investigations to control the static mode either passively with steady disturbances placed around the body (Grandemange, Gohlke & Cadot 2014;Cadot, Evrard & Pastur 2015;Barros et al 2017), with a base cavity (Evrard et al 2016;Lucas et al 2017;Bonnavion & Cadot 2018), with base boat-tailing (Perry, Passmore & Finney 2015;Pavia, Passmore & Gaylard 2016;Bonnavion & Cadot 2019) or actively with flaps (Brackston et al 2016; García de la Cruz, Brackston & Morrison 2017;Brackston, Wynn & Morrison 2018). Overall, three main effects have been observed.…”

Salient three-dimensional features of the turbulent wake of a simplified square-back vehicle

“…Since the seminal work of Grandemange, Gohlke & Cadot (2013b), much progress has been made in the characterisation of the long-time symmetry-breaking bi-stable mode seen in the wakes of simplified square-back bodies (Grandemange, Gohlke & Cadot 2013a;Volpe, Devinant & Kourta 2015;Bonnavion & Cadot 2018;Pavia, Passmore & Sardu 2018). Remarkable progress has also been made in the modelling (Varon et al 2017;Brackston, Wynn & Morrison 2018) and control (Grandemange, Gohlke & Cadot 2014;Evrard et al 2016;Li et al 2016;Perry, Pavia & Passmore 2016b;) of such wakes. The interest of the automotive industry in this topic has also increased following the discovery of similar instabilities in the wakes of more realistic geometries (Grandemange et al 2015;Pavia & Passmore 2017) and even commercially available passenger cars (Bonnavion et al 2017.…”

A New Drag Reduction Method Based on Exhaust Emission Trailing Vortex Control

“…Therefore, in the process of three-dimensional modeling of vehicle external flow field, these factors lead to a sharp increase in the amount of calculation. At the same time, because of the existence of viscous, the boundary layer on the body surface will be generated, which will also be accompanied by the separation of the boundary layer [5].…”