Turbulent coherent structures in an obstructed pipe flow with favorable pressure gradient

A fully-developed turbulent pipe flow at Re_τ = 3400 was perturbed by an axisymmetric obstruction in the center of the pipe, causing favorable pressure gradients and streamline curvature in the flow. The pipe flow was studied with and without the obstruction using particle image velocimetry (PIV). Changes in flow statistics and in the shapes and inclination angles of turbulent coherent structures were observed from the addition of the obstruction. Conditional averaging and proper orthogonal decomposition were used to examine the turbulent structures. This talk will discuss the changes observed in the structures and connect these observations to the existing literature on turbulent coherent structures in favorable pressure gradients. The implications of the results for future reduced-order modeling efforts will be discussed.