Next Article in Journal
Characterization of the Stroke-Induced Changes in the Variability and Complexity of Handgrip Force
Previous Article in Journal
Robust Estimation for the Single Index Model Using Pseudodistances
Article Menu
Issue 5 (May) cover image

Export Article

Open AccessArticle
Entropy 2018, 20(5), 375; https://doi.org/10.3390/e20050375

Transition of Transient Channel Flow with High Reynolds Number Ratios

1
Department of Mechanical Engineering, University of Sheffield, Sheffield S1 3JD, UK
2
Department of Maritime and Mechanical Engineering, Liverpool John Moores University, Liverpool L3 3AF, UK
*
Author to whom correspondence should be addressed.
Received: 24 March 2018 / Revised: 14 May 2018 / Accepted: 15 May 2018 / Published: 17 May 2018

Abstract

Large-eddy simulations of turbulent channel flow subjected to a step-like acceleration have been performed to investigate the effect of high Reynolds number ratios on the transient behaviour of turbulence. It is shown that the response of the flow exhibits the same fundamental characteristics described in He & Seddighi (J. Fluid Mech., vol. 715, 2013, pp. 60–102 and vol. 764, 2015, pp. 395–427)—a three-stage response resembling that of the bypass transition of boundary layer flows. The features of transition are seen to become more striking as the Re-ratio increases—the elongated streaks become stronger and longer, and the initial turbulent spot sites at the onset of transition become increasingly sparse. The critical Reynolds number of transition and the transition period Reynolds number for those cases are shown to deviate from the trends of He & Seddighi (2015). The high Re-ratio cases show double peaks in the transient response of streamwise fluctuation profiles shortly after the onset of transition. Conditionally-averaged turbulent statistics based on a λ_2-criterion are used to show that the two peaks in the fluctuation profiles are due to separate contributions of the active and inactive regions of turbulence generation. The peak closer to the wall is attributed to the generation of “new” turbulence in the active region, whereas the peak farther away from the wall is attributed to the elongated streaks in the inactive region. In the low Re-ratio cases, the peaks of these two regions are close to each other during the entire transient, resulting in a single peak in the domain-averaged profile. View Full-Text
Keywords: pipe flow boundary layer; turbulent transition; large eddy simulation; channel flow pipe flow boundary layer; turbulent transition; large eddy simulation; channel flow
Figures

Figure 1

This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

Share & Cite This Article

MDPI and ACS Style

Mathur, A.; Seddighi, M.; He, S. Transition of Transient Channel Flow with High Reynolds Number Ratios. Entropy 2018, 20, 375.

Show more citation formats Show less citations formats

Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Related Articles

Article Metrics

Article Access Statistics

1

Comments

[Return to top]
Entropy EISSN 1099-4300 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top