Relaminarization of pipe flow by means of 3d-printed shaped honeycombs

TL;DR

This study demonstrates that custom-shaped 3D-printed honeycombs can effectively relaminarize turbulent pipe flow, significantly reducing skin friction and offering potential energy savings at practical pipe lengths.

Contribution

It introduces a novel control method using custom-shaped honeycombs to achieve flow relaminarization, optimizing shape for minimal pressure loss and maximal flow control efficiency.

Findings

Relaminarization achieved at Reynolds number ~10,000.

Skin friction reduced by nearly a factor of 5.

Net energy savings possible at about 100 pipe diameters downstream.

Abstract

Based on a novel control scheme, where a steady modification of the streamwise velocity profile leads to complete relaminarization of initially fully turbulent pipe flow, we investigate the applicability and usefulness of custom-shaped honeycombs for such control. The custom-shaped honeycombs are used as stationary flow management devices which generate specific modifications of the streamwise velocity profile. Stereoscopic particle image velocimetry and pressure drop measurements are used to investigate and capture the development of the relaminarizing flow downstream these devices. We compare the performance of straight (constant length across the radius of the pipe) honeycombs with custom-shaped ones (variable length across the radius). An attempt is made to find the optimal shape for maximal relaminarization at minimal pressure loss. The maximum attainable Reynolds number for total relaminarization is found to be of the order of 10.000. Consequently the respective reduction in skin friction downstream of the device is almost by a factor of 5. The break-even point, where the additional pressure drop caused by the device is balanced by the savings due to relaminarization and a net gain is obtained, corresponds to a downstream stretch of distances as low as approx.\ 100 pipe diameters of laminar flow.