Wall friction and momentum dispersion in free surface flows with non uniform wall roughness
A. Soualmia^{1}, L. Masbernat^{2}*, A. Kaffel^{1} ^{1} Ecole Nationale d’Ingénieurs de Tunis BP 37 Le Belvédère, 1002 Tunis, Tunisie, ^{2} Institut de Mécanique des Fluides de Toulouse, Allée du Professeur Camille Soula 31400, Toulouse, France * Corresponding author. Email: amel.soualmia@ipeim.rnu.tn /masberna@imft.fr /kaffel@vt.edu Received: 25 April 2008; revised version accepted: 08 August 2008
Abstract In this study we analyzed the effects of secondary flows on the transverse distribution of the depth average velocity in free surface flows above nonuniform bottom roughness. In a first preliminary step, 3Dsimulations were achieved using an anisotropic algebraic Reynolds stress model to determine the wall friction and the dispersion terms present in the depth averaged momentum equation. In a second and fundamental step closure assumptions of these terms were tested to define a 2DSaint Venant model which is solved to calculate the transverse profile of the depthaveraged velocity. This approach was applied to opened channels with periodic transverse variation of the roughness with reference to some available experimental results. This process could allow analyze of scale change problems.
Keywords: 2DSaint Venant equations; wall friction; Secondary flows ; roughness; free surface flows; dispersion ; turbulence.

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