Numerical Simulation of Flow and Scour in a Laboratory Junction

Abstract

Confluences are a common feature of riverine systems; the area of converging flow streamlines and potential mixing of separate flows. The hydrodynamics about confluences have a highly complex three-dimensional flow structure. This paper presents the results of a numerical study using the CCHE2D code to investigate the influence of junction angle and discharge ratio on the flow and erosion patterns. The hydraulic and geometric parameters which affect the maximum relative scouring depth are analyzed. The model is first calibrated and validated. Then three discharge ratios, seven junction angles and five width ratios are considered and compared. Results generally agree with experimental data and show that the process of scouring depends on all these parameters. Numerical results demonstrate that a decrease in the ratio of the tributary width to the main channel width results in an increase in the size of the separation zone. Furthermore, the increase in the width ratio leads to a decrease in the maximum depth of bed erosion. Finally, the maximum depth of bed erosion at the confluence increases with the increasing angle of the junction.

Experimental investigation of flow pattern over a fully developed bed at a 60° river confluence in large floods

“…These three categories can be: 1) numerical modeling and/or fieldwork, 2) physical modeling of sediment pattern, and 3) physical modeling of flow pattern. Among the studies that evaluate the flow and sediment patterns of river confluence by numerical modeling and/or fieldwork, one can mention Bradbrook et al (2001), Boyer et al (2006), Shakibainia et al (2010), Constantinescu et al (2011Constantinescu et al ( , 2012, Bahmanpouri et al (2017), Ahadiyan et al (2018), Gualtieri et al (2018), Gualtieri et al (2019), Balouchi et al (2021), Bahmanpouri et al (2022). Besides some studies investigated the effect of geometric and hydraulic conditions on sedimentation pattern such as Ghobadian and Shafai Bejestan (2007), Borghei and Jabbari Sahebari (2010), Balouchi and Shafai Bejestan (2012), Nazari Giglou et al (2016), Amini et al (2017), Wuppukondur and Chandra (2017).…”

Dynamic Equilibrium Position Prediction Model for the Confluence Area of Nakdong River

“…하천 합류부에서는 조건과 환경에 따 라 지류의 퇴적물이 상대적으로 유속이 느린 본류에 진 입하게 되며 발생하는 퇴적 작용으로 삼각주가 형성되기 도 한다. 합류 지역에 생긴 삼각주 지형은, 본류의 형태 와 수리학적 특성에 영향을 주기도 하고 본류의 영향을 받아 형태 변화가 나타나기도 한다 (Savi et al, 2020 Kim, & Ko, 2006;Choi, Mo, & Lee, 2015;Schindfessel, Creëlle, & De Mulder, 2015;Kim & Jang, 2016;C.-L. Jang, 2017;E.-K. Jang & Ji, 2017;Park, Kim, & Baek, 2018;Ahadiyan, Adeli, Bahmanpouri, & Gualtieri, 2018). Eq.…”