Journal of Fluid Mechanics



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Experimental observations of upstream overdeepening


GUIDO ZOLEZZI a1p1, MICHELE GUALA a1, DONATELLA TERMINI a1p2 and GIOVANNI SEMINARA a1
a1 Dipartimento di Ingegneria Ambientale Università di Genova, via Montallegro 1, 16145 Genova, Italy

Article author query
zolezzi g   [Google Scholar] 
guala m   [Google Scholar] 
termini d   [Google Scholar] 
seminara g   [Google Scholar] 
 

Abstract

The issue of morphodynamic influence in meandering streams is investigated through a series of laboratory experiments on curved and straight flumes. Both qualitative and quantitative observations confirm the suitability of the recent theoretical developments (Zolezzi & Seminara 2001) that indicate the occurrence of two distinct regimes of morphodynamic influence, depending on the value of the width ratio of the channel $\beta$. The threshold value $\beta_R$ separating the upstream from the downstream influence regimes coincides with the resonant value discovered by Blondeaux & Seminara (1985). Indeed it is observed that upstream influence may occur only in relatively wide channels, while narrower streams are dominated by downstream influence. A series of experiments has been carried out in order to check the above theoretical predictions and show, for the first time, evidence of the occurrence of upstream overdeepening. Two different sets of experiments have been designed where a discontinuity in channel geometry was present such that the channel morphodynamics was influenced in the upstream direction under super-resonant conditions ($\beta{>}\beta_R$) and in the downstream direction under sub-resonant conditions ($\beta{<}\beta_R$). Experimental results give qualitative and quantitative support to the theoretical predictions and allow us to clarify the limits of the linear analysis.

(Published Online May 18 2005)
(Received January 4 2003)
(Revised October 5 2004)


Correspondence:
p1 Present address: Dipartimento di Ingegneria Civile e Ambientale, Università di Trento, Via Mesiano 77, 38050, Trento, Italy.
p2 Present address: Dipartimento di Ingegneria Idraulica e Applicazioni Ambientali, Università di Palermo, viale delle Scienze, 90128 Palermo, Italy.


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