A detached eddy simulation model for the study of lateral separation zones along a large canyon‐bound river

Abstract

Lateral flow separation occurs in rivers where banks exhibit strong curvature. In canyon‐bound rivers, lateral recirculation zones are the principal storage of fine‐sediment deposits. A parallelized, three‐dimensional, turbulence‐resolving model was developed to study the flow structures along lateral separation zones located in two pools along the Colorado River in Marble Canyon. The model employs the detached eddy simulation (DES) technique, which resolves turbulence structures larger than the grid spacing in the interior of the flow. The DES‐3D model is validated using Acoustic Doppler Current Profiler flow measurements taken during the 2008 controlled flood release from Glen Canyon Dam. A point‐to‐point validation using a number of skill metrics, often employed in hydrological research, is proposed here for fluvial modeling. The validation results show predictive capabilities of the DES model. The model reproduces the pattern and magnitude of the velocity in the lateral recirculation zone, including the size and position of the primary and secondary eddy cells, and return current. The lateral recirculation zone is open, having continuous import of fluid upstream of the point of reattachment and export by the recirculation return current downstream of the point of separation. Differences in magnitude and direction of near‐bed and near‐surface velocity vectors are found, resulting in an inward vertical spiral. Interaction between the recirculation return current and the main flow is dynamic, with large temporal changes in flow direction and magnitude. Turbulence structures with a predominately vertical axis of vorticity are observed in the shear layer becoming three‐dimensional without preferred orientation downstream.

Using an eddy‐resolving technique to assess the effects of reservoir operation on the bend flow in Yangtze River, China

“…Further, the fluctuated velocities illustrated the phenomenon of eddy pulsation, also observed by Alvarez et al. () who used the DES model to study the flow in a sharp bend of the Colorado River in the United States. The time series indicated a cycle of low frequencies of velocities over the 100 to 150 s recurrence interval for both the streamwise and transverse velocities in Figure a,b.…”

“…It is noteworthy that Alvarez et al. () utilized the DES modelling technique to study the turbulence, sediment transport and sandbar beach failure process in the Colorado River, USA. Thus, it was deemed feasible to apply the DES model to study the turbulence in natural rivers using the supercomputer cluster.…”

“…In fact, DES is actually a hybrid technique combining the merits of RANS for near riverbed areas and LES in the flow interior (Constantinescu, Miyawaki, & Rhoads, 2011;Zhang, Liang, & Liu, 2016;Zhang, Ye, & Stanev, 2016), highlighting the relatively lower computational costs compared to the LES models. The DES model has been applied to study river confluence flows (Constantinescu et al, 2011), free surface flows (Zhang, Liang et al, 2016;Zhang, Ye et al, 2016) and sediment transport (Alvarez, Schmeeckle, & Grams, 2017) in idealized or laboratory flumes. It is noteworthy that Alvarez et al (2017) utilized the DES modelling technique to study the turbulence, sediment transport and sandbar beach failure process in the Colorado River, USA.…”

“…The DES model has been applied to study river confluence flows (Constantinescu et al, 2011), free surface flows (Zhang, Liang et al, 2016;Zhang, Ye et al, 2016) and sediment transport (Alvarez, Schmeeckle, & Grams, 2017) in idealized or laboratory flumes. It is noteworthy that Alvarez et al (2017) utilized the DES modelling technique to study the turbulence, sediment transport and sandbar beach failure process in the Colorado River, USA. Thus, it was deemed feasible to apply the DES model to study the turbulence in natural rivers using the supercomputer cluster.…”

Evaluation of aDcp processing options for secondary flow identification at river junctions

“…Dinehart and Burau, 2005;Kasvi et al, 2013;Vermeulen et al, 2014aVermeulen et al, , 2015Engel and Rhoads, 2016;Knox and Latrubesse, 2017;Kasvi et al, 2017;Lotsari et al, 2017;Parsapour-Moghaddam and Rennie, 2018), junctions (e.g. Venditti et al, 2014;Alvarez et al, 2017;Tomas et al, 2018), deltas (e.g. Parsons et al, 2007;Szupiany et al, 2012), canyons (e.g.…”