scholarly journals Numerical investigation of flow and scour around a vertical circular cylinder

2015 ◽  
Vol 373 (2033) ◽  
pp. 20140104 ◽  
Author(s):  
C. Baykal ◽  
B. M. Sumer ◽  
D. R. Fuhrman ◽  
N. G. Jacobsen ◽  
J. Fredsøe
Keyword(s):  
Sediment Transport ◽  
Vortex Shedding ◽  
Large Scale ◽  
Stokes Equations ◽  
Early Stage ◽  
Three Dimensional ◽  
Vertical Cylinder ◽  
Suspended Load ◽  
Frequency Variation ◽  
Suspended Sediment Transport

Flow and scour around a vertical cylinder exposed to current are investigated by using a three-dimensional numerical model based on incompressible Reynolds-averaged Navier–Stokes equations. The model incorporates (i) k - ω turbulence closure, (ii) vortex-shedding processes, (iii) sediment transport (both bed and suspended load), as well as (iv) bed morphology. The influence of vortex shedding and suspended load on the scour are specifically investigated. For the selected geometry and flow conditions, it is found that the equilibrium scour depth is decreased by 50% when the suspended sediment transport is not accounted for. Alternatively, the effects of vortex shedding are found to be limited to the very early stage of the scour process. Flow features such as the horseshoe vortex, as well as lee-wake vortices, including their vertical frequency variation, are discussed. Large-scale counter-rotating streamwise phase-averaged vortices in the lee wake are likewise demonstrated via numerical flow visualization. These features are linked to scour around a vertical pile in a steady current.

Three-Dimensional Flow Structures and Suspended-Sediment Transport in the Dam Area of Large Reservoir

2014 ◽  
Vol 501-504 ◽  
pp. 1981-1985
Author(s):  
Dong Dong Jia ◽  
Jian Yin Zhou ◽  
Xue Jun Shao ◽  
Xi Bao Zhang
Keyword(s):  
Sediment Transport ◽  
Three Dimensional ◽  
Sediment Concentration ◽  
Suspended Load ◽  
Transport Processes ◽  
Flow Structures ◽  
Suspended Sediment Transport ◽  
Large Reservoir ◽  
Secondary Currents ◽  
Load Sediment

The three-dimensional (3-D) flow structures and suspended-load sediment transport processes in the dam area of the Three Gorges Project (TGP) with large water depth were simulated by a 3-D mathematical model. The characteristics of flow structures and suspended-load concentration distribution were analyzed based on the simulated results. Strong 3-D features of flow structures can be found in the dam area, the secondary currents are significant. The suspended-load sediment concentration reduced much faster in wider valley areas, where deposits accumulated. Due to impact of secondary currents, the maximum concentration of suspended-load occurs at the convex side while the minimum at the concave side. It demonstrates that the 3-D numerical modeling is a useful prediction technique and research tool to enhance our understanding of flow structures and mass transport processes in natural rivers with complex boundary.

scholarly journals Suspended Sediment Analysis: Case Study of Berounka Sources

Geografie ◽  
1997 ◽  
Vol 102 (2) ◽  
pp. 130-138
Author(s):  
Zdeněk Kliment ◽  
Jan Kopp
Keyword(s):  
Seasonal Variation ◽  
Sediment Transport ◽  
Suspended Sediment ◽  
Inorganic Material ◽  
Suspended Sediments ◽  
Suspended Load ◽  
Suspended Sediment Transport ◽  
Sediment Analysis ◽  
Load Characteristics

The article examines suspended sediment transport in Mže, Radbuza, and Úhlava Rivers over the period 1989-95. Data on suspended sediments was collected at five observing sites. The research has been carried out in collaboration with Czech Hydrometeorological Institute, Plzeň. Apart from the suspended load characteristics also the seasonal variation of suspended sediments, siltation of Hracholusky and České Údolí Lakes, and the share of inorganic material in suspended sediments have been examined.

Numerical simulations of three-dimensional plunging breaking waves: generation and evolution of aerated vortex filaments

2015 ◽  
Vol 767 ◽  
pp. 364-393 ◽  
Author(s):  
P. Lubin ◽  
S. Glockner
Keyword(s):  
Stokes Equations ◽  
Early Stage ◽  
Flow Direction ◽  
Three Dimensional ◽  
Air Entrainment ◽  
Breaking Waves ◽  
Navier Stokes ◽  
Vortex Filaments ◽  
Navier Stokes Equations ◽  
Main Flow Direction

AbstractThe scope of this work is to present and discuss the results obtained from simulating three-dimensional plunging breaking waves by solving the Navier–Stokes equations, in air and water. Recent progress in computational capabilities has allowed us to run fine three-dimensional simulations, giving us the opportunity to study for the first time fine vortex filaments generated during the early stage of the wave breaking phenomenon. To date, no experimental observations have been made in laboratories, and these structures have only been visualised in rare documentary footage (e.g. BBC 2009 South Pacific. Available on YouTube, 7BOhDaJH0m4). These fine coherent structures are three-dimensional streamwise vortical tubes, like vortex filaments, connecting the splash-up and the main tube of air, elongated in the main flow direction. The first part of the paper is devoted to the presentation of the model and numerical methods. The air entrainment occurring when waves break is then carefully described. Thanks to the high resolution of the grid, these fine elongated structures are simulated and explained.

scholarly journals Effect of Inclination Angles on the Local Scour around a Submerged Cylinder

Water ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2687
Author(s):  
Shaohua Wang ◽  
Shiyu Yang ◽  
Zhiguo He ◽  
Li Li ◽  
Yuezhang Xia
Keyword(s):  
Inclination Angle ◽  
Stokes Equations ◽  
Transport Model ◽  
Three Dimensional ◽  
Vertical Cylinder ◽  
Horseshoe Vortex ◽  
Local Scour ◽  
Scour Depth ◽  
Ocean Engineering ◽  
Bed Morphology

In ocean engineering and coastal environmental studies, local scour around a submerged structure is a typical issue, which is affected by the inclination of the structure. To investigate the effect of inclination directions and angles on flow structure and the bed morphology, a three-dimensional numerical model of a submerged inclined cylinder was established. In this model, the hydrodynamics are solved from the RANS (Reynolds-averaged Navier–Stokes) equations closed with the RNG k-ε turbulence model, while the bed morphology evolution is captured by the sediment transport model. In the case of vertical-cylinder scour, the simulation results agree well with existing laboratory experiments. In the cases of inclined-cylinder scour, the results show that the inclination direction not only changes the intensity and the location of the downflow but also modulates the pattern of the horseshoe vortex in front of the cylinder, thus influencing the local scour depth and the morphology of the bed. Compared with the case of vertical cylinder, the scour around an upstream-inclined cylinder is deeper, mainly due to the enhancement of downflow in front of the cylinder. The scour around a downstream-inclined cylinder is shallower and broader due to the weakened downflow and accelerated incoming flow. The maximum scour depth decreases with the inclination angle in the downstream-inclination case. In the upstream-inclination case, the maximum scour depth does not vary monotonously with the inclination angle, which results from a competitive effect of the horseshoe vortex and downflow in the front of the cylinder.

scholarly journals 3D Modeling and Mechanism Analysis of Breaking Wave-Induced Seabed Scour around Monopile

2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Xiaojian Liu ◽  
Cheng Liu ◽  
Xiaowei Zhu ◽  
Yong He ◽  
Qisong Wang ◽  
...  
Keyword(s):  
Shear Stress ◽  
Sediment Transport ◽  
Stokes Equations ◽  
Volume Fraction ◽  
Laboratory Data ◽  
Suspended Load ◽  
Breaking Wave ◽  
Offshore Structure ◽  
Nearshore Sediment Transport ◽  
Wave Induced

Breaking wave-induced scour is recognized as one of the major causes of coastal erosion and offshore structure failure, which involves in the full 3D water-air-sand interaction, raising a great challenge for the numerical simulation. To better understand this process, a nonlinear 3D numerical model based on the open-source CFD platform OpenFOAM® was self-developed in this study. The Navier–Stokes equations were used to compute the two-phase incompressible flow, combining with the finite volume method (FVM) to discretize calculation domain, a modified VOF method to track the free surface, and a k−ε model to closure the turbulence. The nearshore sediment transport process is reproduced in view of shear stress, suspended load, and bed load, in which the terms of shear stress and suspended load were updated by introducing volume fraction. The seabed morphology is updated based on Exner equation and implemented by dynamic mesh technique. The mass conservative sand slide algorithm was employed to avoid the incredible vary of the bed mesh. Importantly, a two-way coupling method connecting the hydrodynamic module with the beach morphodynamic module is implemented at each computation step to ensure the fluid-sediment interaction. The capabilities of this model were calibrated by laboratory data from some published references, and the advantages/disadvantages, as well as proper recommendations, were introduced. Finally, nonbreaking- and breaking wave-induced scour around the monopile, as well as breaking wave-induced beach evolution, were reproduced and discussed. This study would be significantly helpful to understand and evaluate the nearshore sediment transport.

scholarly journals Large-scale suspended sediment transport and sediment deposition in the Mekong Delta

2014 ◽  
Vol 18 (8) ◽  
pp. 3033-3053 ◽  
Author(s):  
N. V. Manh ◽  
N. V. Dung ◽  
N. N. Hung ◽  
B. Merz ◽  
H. Apel
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Large Scale ◽  
Transport Model ◽  
Mekong Delta ◽  
Sediment Dynamics ◽  
Sediment Deposition ◽  
Mineral Fertilizers ◽  
Suspended Sediment Transport ◽  
Extreme Flood

Abstract. Sediment dynamics play a major role in the agricultural and fishery productivity of the Mekong Delta. However, the understanding of sediment dynamics in the delta, one of the most complex river deltas in the world, is very limited. This is a consequence of its large extent, the intricate system of rivers, channels and floodplains, and the scarcity of observations. This study quantifies, for the first time, the suspended sediment transport and sediment deposition in the whole Mekong Delta. To this end, a quasi-2D hydrodynamic model is combined with a cohesive sediment transport model. The combined model is calibrated using six objective functions to represent the different aspects of the hydraulic and sediment transport components. The model is calibrated for the extreme flood season in 2011 and shows good performance for 2 validation years with very different flood characteristics. It is shown how sediment transport and sediment deposition is differentiated from Kratie at the entrance of the delta on its way to the coast. The main factors influencing the spatial sediment dynamics are the river and channel system, dike rings, sluice gate operations, the magnitude of the floods, and tidal influences. The superposition of these factors leads to high spatial variability of sediment transport, in particular in the Vietnamese floodplains. Depending on the flood magnitude, annual sediment loads reaching the coast vary from 48 to 60% of the sediment load at Kratie. Deposited sediment varies from 19 to 23% of the annual load at Kratie in Cambodian floodplains, and from 1 to 6% in the compartmented and diked floodplains in Vietnam. Annual deposited nutrients (N, P, K), which are associated with the sediment deposition, provide on average more than 50% of mineral fertilizers typically applied for rice crops in non-flooded ring dike floodplains in Vietnam. Through the quantification of sediment and related nutrient input, the presented study provides a quantitative basis for estimating the benefits of annual Mekong floods for agriculture and fishery, and is an important piece of information with regard to the assessment of the impacts of deltaic subsidence and climate-change-related sea level rise on delta morphology.

A Benchmark Comparison of Coupled and Segregated Iterative SUPG Finite Element Formulation for Incompressible Flow

2006 ◽  
Author(s):  
Jianhui Xie ◽  
R. S. Amano
Keyword(s):  
Finite Element ◽  
Large Scale ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Cost Effective ◽  
Element Formulation ◽  
Application Problem ◽  
The Individual ◽  
Solution Efficiency ◽  
Fully Coupled

In fluid flow and heat transfer, the finite element based fully coupling solution for all conservation equations is cost effective for most of the two dimensional, isothermal problems, but suffers in the storage and solution efficiency for large three dimensional problems. The segregated solution algorithm has been designed to address large scale simulation with avoiding the direct formulation of a global matrix. There is trade-off between performing a large number of less expensive iterations by segregated solvers compared to less number of more expensive fully coupled solvers. In this paper, a Finite Element based scheme based on preconditioned GMRES coupled algorithm and SUPG (Streamline Upwind Petrov-Galerkin) pressure prediction/correction segregated formulations have been discussed to solve the steady Navier-Stokes equations. A systematic comparison and benchmark between the segregated and fully coupled formulation has been presented to evaluate the individual benefits and strengths of the coupling and segregated procedure by studying lid-driven cavity problem and large industry application problem with respect to the system storage and solution convergence.

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