Temporal acceleration of a turbulent channel flow

Akshat Mathur, Sam Gorji, Shuisheng He, Mehdi Seddighi, Alan Vardy, Thomas O'Donoghue, Dubravka Pokrajac

Research output: Contribution to journalArticle

5 Citations (Scopus)
20 Downloads (Pure)

Abstract

We report new laboratory experiments of a flow accelerating from an initially turbulent state following the opening of a valve, together with large eddy simulations of the experiments and extended Stokes first problem solutions for the early stages of the flow. The results show that the transient flow closely resembles an accelerating laminar flow superimposed on the original steady turbulent flow. The primary consequence of the acceleration is the temporal growth of a boundary layer from the wall, gradually leading to a strong instability causing transition. This extends the findings of previous DNS simulations of transient flow following a near-step increase in flow rate. In this interpretation, the initial turbulence is not the primary characteristic of the resulting transient flow, but can be regarded as noise the evolution of which is strongly influenced by the development of the boundary layer. We observe the spontaneous appearance of turbulent spots and discontinuities in the velocity signals in time and space, revealing rich detail of the transition process, including a striking contrast between streamwise and wall-normal fluctuating velocities.
Original languageEnglish
Pages (from-to)471-490
Number of pages20
JournalJournal of Fluid Mechanics
Volume835
Early online date27 Nov 2017
DOIs
Publication statusPublished - Jan 2018

Keywords

  • Pipe flow boundary layer < Boundary Layers
  • Turbulent transition < Turbulent Flows

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