Steady streamwise transpiration control in turbulent pipe flow

TL;DR

This paper investigates how steady streamwise wall transpiration affects turbulent pipe flow, revealing configurations that can significantly reduce or increase flow rate, supported by direct numerical simulations and resolvent analysis.

Contribution

It provides new insights into flow control via wall transpiration, linking parameters to flow behavior and flow rate modifications in turbulent pipe flow.

Findings

Flow rate can be reduced by 36.1% or increased by 19.3% through transpiration.

Transpiration parameters influence Reynolds shear stress, streaming, and mean gradients.

Flow structure reorganization is characterized by resolvent analysis.

Abstract

A study of the the main features of low- and high amplitude steady streamwise wall transpiration applied to pipe flow is presented. The effect of the two transpiration parameters, amplitude and wavenumber, on the flow have been investigated by means of direct numerical simulation at a moderate turbulent Reynolds number. The behaviour of the three identified mechanisms that act in the flow: modification of Reynolds shear stress, steady streaming and generation of non-zero mean streamwise gradients, have been linked to the transpiration parameters. The observed trends have permitted the identification of wall transpiration configurations able to reduce or increase the overall flow rate in -36.1% and 19.3% respectively. A resolvent analysis has been carried out to obtain a description of the reorganization of the flow structures induced by the transpiration.