Control of the separated flow downstream of a backward-facing step using visual feedback

The separated flow downstream of a backward-facing step is controlled using visual information for feedback. This is done when looking at the flow from two vantage points. Flow velocity fields are computed in real time and used to yield inputs to a control loop. This approach to flow control is shown to be able to control the detached flow in the same way as has been done before by using the area of the recirculation region downstream of the step as the input for a gradient descent optimization scheme. Visual feedback using real-time computations of two-dimensional velocity fields also allows for novel inputs in the feedback scheme. As a proof of concept, the spatially averaged value of the swirling strength lambda(Ci) is successfully used as the input for an automatically tuned proportional-integral-derivative controller.