Transport Phenomena and Fluid Mechanics

Characteristic time scales for predicting the scalar flux at a free surface in turbulent open-channel flows

  1. Ryuichi Nagaosa1,2,*,
  2. Robert A. Handler3

Article first published online: 1 MAR 2012

DOI: 10.1002/aic.13773

Issue

AIChE Journal

AIChE Journal

Volume 58, Issue 12, pages 3867–3877, December 2012

Additional Information

How to Cite

Nagaosa, R. and Handler, R. A. (2012), Characteristic time scales for predicting the scalar flux at a free surface in turbulent open-channel flows. AIChE J., 58: 3867–3877. doi: 10.1002/aic.13773

Author Information

  1. 1

    Research Center for Compact Chemical System (CCS), AIST, Miyagino, Sendai 983-8551, Japan

  2. 2

    Center for Environmental Energy Engineering (CEEE), University of Maryland, College Park, MD 20742

  3. 3

    Dept. of Mechanical Engineering, Texas A&M University, College Station, TX 77843

*Center for Environmental Energy Engineering (CEEE), University of Maryland, College Park, MD 20742

Publication History

  1. Issue published online: 8 NOV 2012
  2. Article first published online: 1 MAR 2012
  3. Accepted manuscript online: 10 FEB 2012 11:50AM EST
  4. Manuscript Revised: 31 JAN 2012
  5. Manuscript Received: 8 MAY 2011

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Keywords:

  • computational fluid dynamics;
  • fluid mechanics;
  • scalar transfer;
  • turbulence;
  • interfacial processes

Abstract

The purpose of this study is to predict the turbulent scalar flux at a free surface subject to a fully developed turbulent flow based on a hydrodynamic analysis of turbulence in the region close to the free surface. The effect of the Reynolds number on turbulent scalar transfer mechanisms is extensively examined. A direct numerical simulation technique is applied to achieve the purpose. The surface-renewal approximation is used to correlate the free-surface hydrodynamics and scalar transport at the free surface. Two types of characteristic time scales have been examined for predicting turbulent scalar flux. One is the time scale derived from the characteristic length and velocity scale at the free surface. The other is the reciprocal of the root-mean-square surface divergence. The results of this study show that scalar transport at the free surface can be predicted successfully using these time scales based on the concept of the surface-renewal approximation. © 2012 American Institute of Chemical Engineers AIChE J, 2012

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