Flow Analysis of a River Confluence with Field Measurements and Rans Model with Nested Grid Approach

Abstract

A comprehensive flow analysis for a confluence of two medium‐sized (Qmean ≈ 30–50 m3/s) Hungarian rivers was carried out by means of a three‐dimensional Reynolds‐averaged Navier–Stokes modelling. The model was validated against detailed fixed and moving Acoustic Doppler Current Profiler velocity profiling. Unsteady simulations with steady‐state boundary conditions were performed on a structured grid in order to reveal the characteristic large‐scale spatial behaviour of the flow, such as strong secondary currents because of the river bends upstream of the confluence. Secondary current vectors indicating the swirling character of the flow were derived both from field measurements and model results showing good agreements for two different discharge ratios. Additionally, a novel approach was used to simulate the unsteady vortex shedding implementing a nested grid into the previously used coarse grid. Using a considerable finer horizontal (~0.5 m) and time (1 s) resolution, the numerical model reproduced the unsteady character of flow between the two rivers. A qualitative assessment of the mixing processes was also introduced through the example of the propagation of plaster plume used to neutralize a disastrous red mud spillage that occurred in 2010. The results indicate the combined influence of secondary currents and vortex shedding. Copyright © 2013 John Wiley & Sons, Ltd.

Habitat mapping of riverine fish by means of hydromorphological tools

“…The computational hydrodynamic model used in this research (Olsen, 2010) had already been tested and validated in many riverine flow and sediment transport studies. These applications focused on FIGURE 2 Grain size distribution curves of the bed material samples (the sampling locations of Samples 1-4 are indicated in Figure 1b) the analysis of hydraulic structures (e.g., Haun, Olsen, & Feurich, 2011;Olsen & Kjellesvig, 1998); simulation of reservoir flushing (e.g., Haun & Olsen, 2012;Olsen, Jimenez, Abrahamsen, & Løvoll, 1999); laboratory scale simulations (e.g., Baranya & Józsa, 2007;Baranya, Olsen, Stoesser, & Sturm, 2012;Ruether & Olsen, 2005); river flow simulations (e.g., Baranya & Józsa, 2006;Olsen & Stokseth, 1995;Wilson, Yagci, Rauch, & Olsen, 2006); simulation of mixing in rivers (e.g., Baranya, Olsen, & Józsa, 2015); and simulation of river morphodynamics (e.g., Baranya, 2010;Fischer-Antze, Olsen, & Gutknecht, 2008). The numerical model solves the so-called Reynolds-averaged Navier-Stokes equations on a horizontally structured, curvilinear grid system.…”

On the Simulation of Floods in a Narrow Bending Valley: The Malpasset Dam Break Case Study

“…CFD models simulate effectively fluvial settings characterized by high hydrodynamic complexity [29,30]. For instance, Baranya et al [31] used CFD for simulating confluences of two medium-sized Hungarian rivers through a 3D Reynolds-averaged Navier-Stokes (RANS) model.…”

Numerical study of junction-angle effects on flow pattern in a river confluence located in a river bend

“…Yang (2013) used a numerical model with a dynamic meshwork to investigate the flow characteristics in a 90° junction; the comparison between the model and experimental results revealed that the model is highly capable of predicting the water level and velocity values. Baranya et al (2013), by means of a 3-dimensional Reynolds-averaged Navier-Stokes model, carried out a comprehensive flow analysis for a confluence of 2 medium-sized Hungarian rivers. They converted a nested grid into a coarse grid to simulate unsteady vortex shading.…”

“…The use of numerical models for simulating the flow in river junctions has recently attracted researchers' attention, such as Weerakoon et al (1991), Huang et al (2002), Biron et al (2004) and Chen and Peng (2006). Weerakoon et al (1991) used a fully elliptic treatment in study of a 60° asymmetrical confluence.…”

“…He first compared the simulation results for q*= 0.25 and q*= 0.75 with Weber's experimental data; then he examined the effect of the junction angle on the flow characteristics. Biron et al (2004) used a 3-dimensional model to examine mixing processes immediately downstream of confluence as well as further downstream in the mainstream. Simulations are presented for concordant and discordant laboratory junction and a field confluence for a low and a high flow condition.…”