Open-loop control of three-dimensional wakes

Abstract

This chapter presents a paper that demonstrates the problem of wake optimization on the generic case of the 3D cylinder. It provides a description of the numerical method, several optimization strategies, aiming at identifying vortex systems providing drag reduction or special topology of the flow. This chapter considers strategies as simple as cylinder rotation or bidimensional stationary profiles of velocity and presents an outlook of full 3D tangential controls, which may be mixed or not with simple strategies. The control of wakes is a subject of paramount importance in aircraft and automobile industry. Wake control can have various goals and can be achieved either by passive or active strategies. Passive control mostly operates through shape optimization and often results in the addition of appendices such as foilers or ribblets to the surface of an obstacle. Active control implies that one is ready to impart energy on the flow by means of actuators on the surface of the obstacle, keeping in mind that this energy must be included in the global energy budget to conclude on the efficiency of the particular control strategy. This paper presents a robust numerical method, a high-order vortex-in-cell scheme, and its application to the open loop control of three-dimensional wakes.