Experiments on transient growth of turbulent spots

TL;DR

This paper investigates the transient growth of turbulent spots in plane Couette-Poiseuille flow through experiments and linear theory, comparing results and exploring the limits of linear approximation at high perturbations and Reynolds numbers.

Contribution

It provides a combined experimental and theoretical analysis of turbulent spot growth, highlighting the validity limits of linear transient growth theory in complex flow conditions.

Findings

Quantitative comparison of experimental and theoretical maximal gain.

Identification of the time at which transient growth peaks.

Demonstration of the limits of linear theory at high perturbation amplitudes.

Abstract

We present detailed experiments on transient growth of turbulent spots induced by external forcing in plane Couette-Poiseuille flow, which are studied in the framework of linear of transient growth. The experimental investigation is supplemented with full theoretical analysis. We compare quantitatively the experimental and theoretical results, including maximal gain and the time at which it occurs. We also present the limits of validity for the application of the linear theory at high amplitude perturbation and Reynolds number, showing experiments with self-sustained states.