The Role of Vortex Stretching in Drag Reduction of Polymer-Laden Turbulent Flow

TL;DR

This paper investigates how polymers reduce drag in turbulent flows by diminishing vortex stretching, deriving a theoretical mean-velocity profile, and validating it through numerical and experimental data.

Contribution

It introduces a theoretical model linking polymer-induced vortex stretching reduction to drag decrease, supported by numerical and experimental validation.

Findings

The theory accurately predicts mean velocity profiles in drag-reduced flows.

Numerical experiments confirm the role of vortex stretching reduction.

Experimental data aligns with the theoretical predictions.

Abstract

An addition of polymers can significantly reduce drag in wall-bounded turbulent flows, such as pipes or channels. This phenomenon is accompanied by a noticeable modification of the mean velocity profile. Starting from the premise that polymers reduce vortex-stretching, we derive a theoretical prediction for the mean-velocity profile. After assessing this prediction by numerical experiments of turbulence with reduced vortex stretching, we show that the theory successfully describes experimental measurements of drag-reduction in pipe-flow.