Wall pressure fluctuations associated with complex flows.

The relationship between wall pressure fluctuations and turbulent structures in a boundary layer has been the subject of research for well over three decades. In that time, the focus of attention was for the canonical case of an equilibrium boundary layer. These studies have identified the causalities between the near‐wall flow structures and the high‐frequency pressures, and the outer‐flow structures and the low‐frequency pressures. For complex flows, the characteristics of the turbulence activities within the boundary layer have unique structures that are distinct from the canonical case. Accordingly, the features of the wall pressure field are quite different. As an example of a complex flow, the fluctuating wall pressures and turbulence statistics measured downstream of a backward facing step will be presented and compared to an equilibrium flow. The data demonstrate that the elevated low‐frequency pressures directly track coherent turbulence structures in the flow field that result from passage over ...