Flow physics and control of trapped vortex cell flows

The main objective of this work is to investigate on the physics and on the control of the flow in a Trapped Vortex Cell, often referred to as TVC in the following. A TVC is a cavity with a particular geometry, which is optimised to trap a vortical structure. This configuration has recently gained interest has a device to control the flow past thick airfoils, but fundamental research is still required to make this technique effective. Specifically, a first goal of this work is to investigate on the fundamental physics of this flow, by studying the basic elements and the dominant phenomena. In fact, this flow field is the result of the complex interaction of several flows, such as the upstream boundary layer, the shear layer detaching from the cavity leading edge, the vortex core, and the boundary layer developing downstream. A further issue of interest addressed in this work is that related to the role of unsteadiness of the cell flow, and in particular of the shear layer, whose self-sustained oscillations are a common feature of open-cavity flows. The understanding of the driving physical mechanisms of the base flow is required to successfully proceed in developing a control strategy aiming at the control of the flow, because it is necessary to manipulate this flow in order to make the TVC an effective control device. Therefore, a second goal is to study and compare two different control techniques targeting the cavity flow. The first of the two is steady suction of the flow in the cell and has been already applied in past researches, but some additional insight into its effects on the base flow is required. The second proposed control technique is open-loop control with a synthetic jet actuator, a more efficient device whose unsteady action can couple to or drive the relevant mechanisms of the flow. Furthermore, open-loop control studies with a synthetic jet are propaedeutic for closed-loop control of the flow, briefly investigated in the last part of research.