Response and recovery of turbulent pipe flow past a streamlined body of revolution

The response and recovery of a turbulent pipe flow perturbed by a streamlined body of resolution will be presented. The flow upstream of the body is fully developed with a bulk Reynolds number of 167,000. Three body diameters with blockage ratios of 1/9, 2/9 and 1/3 were employed to vary the perturbation strength. PIV data were collected in the region of the body and at downstream distances up to 120 pipe radii to comprehensively characterize the flow behaviors. Over the body, the flow experiences pressure gradients and streamline curvature and divergence/convergence. The responses of the mean flow and turbulent structures in this region are decoupled because the body perturbs the flow with a time scale much shorter than the turbulence time scale. In the wake, the flow development is initially fast by the mean pressure but then undergoes a slow and oscillatory recovery. The latter is a result of the asynchronous recovery between the mean flow and the turbulence, and it has been commonly observed in perturbed wall-bounded flows. A RANS-based model that was developed for recovering pipe flows is examined against the present case to test its validity.