Tumbling of a Brownian particle in an extensional flow

TL;DR

This paper investigates whether tumbling occurs in extensional flows by studying a semi-flexible trumbbell, revealing that tumbling can happen through folding with exponential distribution of tumbling times increasing with flow strength.

Contribution

It demonstrates that tumbling is possible in stretching flows and characterizes its statistical properties, extending understanding beyond shear flow scenarios.

Findings

Tumbling occurs via folding in extensional flows.

Tumbling time distribution is exponential.

Tumbling times increase exponentially with Weissenberg number.

Abstract

The phenomenon of tumbling of microscopic objects is commonly associated with shear flows. We address the question of whether tumbling can also occur in stretching-dominated flows. To answer this, we study the dynamics of a semi-flexible trumbbell in a planar extensional velocity field. We show that the trumbbell undergoes a random tumbling-through-folding motion. The probability distribution of long tumbling times is exponential with a time scale exponentially increasing with the Weissenberg number.