Modelling of the tributary momentum contribution to predict confluence head losses

Abstract

This paper proposes a new model to determine the head losses at confluences in one-dimensional models of open channel networks, making use of a momentum conservation approach. Momentum conservation has been applied in several theoretical models for confluence head losses, giving satisfactory results in general. However, for larger confluence angles between the main channel and the incoming tributary, the model accuracy diminished. Many authors identified that a correct estimation of the tributary momentum contribution is a prerequisite for accurate results. This work reports on the development and application of a theoretical model for the tributary momentum contribution, based on similarities with the flow upstream of a circular bend in a straight open channel. It describes the two-dimensional depth-averaged flow features in the tributary under the assumption of a 90° angle confluence in which all channels have equal widths, in order to obtain the resulting momentum contribution. The proposed model predicts head losses within the same order of accuracy as a numerical model solving the shallow water equations in two dimensions throughout the confluence

Dynamics of Flow at Concordant Gravel Bed River Confluences: Effects of Junction Angle and Momentum Flux Ratio

“…Previous field, experimental, and numerical research succeeded in producing several conceptual models of flow structure at confluences (Mosley, 1976;Best, 1987;Best & Roy, 1991;Ashmore et al, 1992;Paola, 1997;. However, studies focusing on theoretical generalizations are rare and have examined only a few relations between bulk flow variables under idealized hydraulic conditions (Chu & Babarutsi, 1988;Creēlle et al, 2017;Hager, 1987Hager, , 1989aHager, , 1989bModi et al, 1981;Taylor, 1944;Uijttewaal & Booij, 2000). The lack of general theory in this area of research leaves room for differences of opinion about mechanisms driving the dynamics of flow at river confluences.…”

Numerical Modeling for Hydrodynamics and Near-Surface Flow Patterns of a Tidal Confluence

“…Extensive research has been carried out to understand different aspects of river science and open channel flow through field studies (Lamarre and Roy, 2008), physical models (Kasprak et al, 2015), numerical models (Hardy et al, 2003), and flume studies (Nelson and Morgan, 2018). However, the role of a confluence in integrated river management has only been identified recently, especially regarding the reciprocal adjustment of flow, sediment, and resulting morphological changes (Best, 1986;Biron et al, 1993;Creelle, Schindfessel, and De Mulder, 2017;Dordevic and Stojnic, 2016;Gaudet and Roy, 1995;Guillén Lude ña et al, 2017;Schindfessel, Creelle, and De Mulder, 2015;Tancock, 2014). Best (1986) noted that morphological features of different intersection geometries are not similar.…”

“…The purpose of this research is to discover more about the hydrodynamics of the confluent areas affected by tides. Existing literature (e.g., studies by De Mulder, 2017, andLuo et al, 2018) regarding the confluence implicitly assumes an exclusive unidirectional flow. Creelle, Schindfessel, and De Mulder (2017) presented a new onedimensional (1D) model to estimate the head loss of merging streams by using momentum conservation.…”

“…Existing literature (e.g., studies by De Mulder, 2017, andLuo et al, 2018) regarding the confluence implicitly assumes an exclusive unidirectional flow. Creelle, Schindfessel, and De Mulder (2017) presented a new onedimensional (1D) model to estimate the head loss of merging streams by using momentum conservation. Luo et al (2018) performed numerical simulations to predict the effect of different controls on energy losses in the postconfluence channel.…”