Controlling the onset of turbulence by streamwise traveling waves. Part 1: Receptivity analysis

TL;DR

This paper investigates how streamwise traveling waves generated by surface blowing and suction can effectively control the onset of turbulence in channel flow, using a theoretical approach validated by simulations.

Contribution

It introduces a weakly nonlinear analysis and receptivity analysis for designing traveling waves that reduce flow receptivity, aiding turbulence control.

Findings

Downstream traveling waves reduce receptivity to disturbances.

Upstream traveling waves increase receptivity.

Theoretical predictions match full-scale nonlinear simulations.

Abstract

We examine the efficacy of streamwise traveling waves generated by a zero-net-mass-flux surface blowing and suction for controlling the onset of turbulence in a channel flow. For small amplitude actuation, we utilize weakly nonlinear analysis to determine base flow modifications and to assess the resulting net power balance. Receptivity analysis of the velocity fluctuations around this base flow is then employed to design the traveling waves. Our simulation-free approach reveals that, relative to the flow with no control, the downstream traveling waves with properly designed speed and frequency can significantly reduce receptivity which makes them well-suited for controlling the onset of turbulence. In contrast, the velocity fluctuations around the upstream traveling waves exhibit larger receptivity to disturbances. Our theoretical predictions, obtained by perturbation analysis (in the wave amplitude) of the linearized Navier-Stokes equations with spatially periodic coefficients, are verified using full-scale simulations of the nonlinear flow dynamics in companion paper, Lieu, Moarref & Jovanovi\'c (2010).