Conditions for tidal bore formation in convergent alluvial estuaries

详细信息    查看全文

• 作者：Philippe Bonneton^a ; ^{p.bonneton@epoc.u-bordeaux1.fr" class="auth_mail" title="E-mail the corresponding author} ; Andrea Gilberto Filippini^b ; ^{andrea.filippini@inria.fr" class="auth_mail" title="E-mail the corresponding author} ; Luca Arpaia^b ; ^{luca.arpaia@inria.fr" class="auth_mail" title="E-mail the corresponding author} ; Natalie Bonneton^a ; ^{n.bonneton@epoc.u-bordeaux1.fr" class="auth_mail" title="E-mail the corresponding author} ; Mario Ricchiuto^b ; ^{Mario.Ricchiuto@inria.fr" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Tidal wave ; Tidal bore ; Estuary ; River ; Scaling analysis ; Classification
• 刊名：Estuarine, Coastal and Shelf Science
• 出版年：2016
• 出版时间：5 April 2016
• 年：2016
• 卷：172
• 期：Complete
• 页码：121-127
• 全文大小：982 K

文摘

Over the last decade there has been an increasing interest in tidal bore dynamics. However most studies have been focused on small-scale bore processes. The present paper describes the first quantitative study, at the estuary scale, of the conditions for tidal bore formation in convergent alluvial estuaries. When freshwater discharge and large-scale spatial variations of the estuary water depth can be neglected, tide propagation in such estuaries is controlled by three main dimensionless parameters: the nonlinearity parameter class="mathmlsrc">class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0272771416300191&_mathId=si1.gif&_user=111111111&_pii=S0272771416300191&_rdoc=1&_issn=02727714&md5=099ff47ed4afa130a3793720cb840802" title="Click to view the MathML source">ε₀class="mathContainer hidden">class="mathCode">${\mathit{\epsilon }}_0$, the convergence ratio δ₀ and the friction parameter ϕ₀. In this paper we explore this dimensionless parameter space, in terms of tidal bore occurrence, from a database of 21 estuaries (8 tidal-bore estuaries and 13 non tidal-bore estuaries). The field data point out that tidal bores occur for convergence ratios close to the critical convergence δ_c. A new proposed definition of the friction parameter highlights a clear separation on the parameter plane (ϕ₀,class="mathmlsrc">class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0272771416300191&_mathId=si1.gif&_user=111111111&_pii=S0272771416300191&_rdoc=1&_issn=02727714&md5=099ff47ed4afa130a3793720cb840802" title="Click to view the MathML source">ε₀class="mathContainer hidden">class="mathCode">${\mathit{\epsilon }}_0$) between tidal-bore estuaries and non tidal-bore estuaries. More specifically, we have established that tidal bores occur in convergent estuaries when the nonlinearity parameter is greater than a critical value, class="mathmlsrc">class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0272771416300191&_mathId=si24.gif&_user=111111111&_pii=S0272771416300191&_rdoc=1&_issn=02727714&md5=1e6343d2bcd5de5df771ca3106fbc1f3" title="Click to view the MathML source">ε_cclass="mathContainer hidden">class="mathCode">${\mathit{\epsilon }}_c$, which is an increasing function of the friction parameter ϕ₀. This result has been confirmed by numerical simulations of the two-dimensional Saint Venant equations. The real-estuary observations and the numerical simulations also show that, contrary to what is generally assumed, tide amplification is not a necessary condition for tidal bore formation. The effect of freshwater discharge on tidal bore occurrence has been analyzed from the database acquired during three long-term campaigns carried out on the Gironde/Garonne estuary. We have shown that in the upper estuary the tidal bore intensity is mainly governed by the local dimensionless tide amplitude ε. The bore intensity is an increasing function of ε and this relationship does not depend on freshwater discharge. However, freshwater discharge damps the tidal wave during its propagation and thus reduces ε and consequently limits the tidal bore development in the estuary. To take into account this process in the tidal-bore scaling analysis, it is necessary to introduce a fourth external parameter, the dimensionless river discharge class="mathmlsrc">class="formulatext stixSupport mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0272771416300191&_mathId=si3.gif&_user=111111111&_pii=S0272771416300191&_rdoc=1&_issn=02727714&md5=f4f3d95c257986186a4678a3da59cb7a" title="Click to view the MathML source">Q₀class="mathContainer hidden">class="mathCode">${\mathcal{Q}}_0$.