Flow separation control on a backward facing step using wall information*

Flow separation, characterized by the formation of recirculation zones within

a boundary layer, significantly impacts the efficiency of aerospace, automotive,

marine, and turbo-machinery systems. Most studies have focused on active con-

trol strategies to mitigate flow separation, but the potential of passive control

using wall information still remains under-explored. In this work, we investigate

flow separation control on the benchmark problem of a backward-facing step,

leveraging wall information, specifically wall shear stress. The use of wall infor-

mation enhances the practicality of the study, paving the way for the potential

application of passive surface metamaterials in flow separation control. The cur-

rent work presents the results of Direct Numerical Simulations of a turbulent

flow over a backward-facing step with and without the flow control. Control is

applied via a transpiration wall velocity, whose value is computed based on a

local wall shear stress information, at various locations along the step surface.

The influence of the control location on the ability of this approach to reduce

flow separation is investigated. Turbulent flow statistics and results of proper

orthogonal decomposition are presented.