scholarly journals RIDGE-RUNNEL MIGRATION

2012 ◽  
Vol 1 (33) ◽  
pp. 46
Author(s):  
Jens Figlus ◽  
Nobuhisa Kobayashi ◽  
Christine Gralher
Keyword(s):  
Free Surface ◽  
Sediment Transport ◽  
Numerical Model ◽  
Fluid Velocity ◽  
Transport Mechanisms ◽  
Free Surface Elevation ◽  
Wave Flume ◽  
Mobile Bed ◽  
Dry Zone ◽  
Insight Into

The recovery of beaches after a storm can be influenced significantly by ridge-runnel migration. Ridges are made up of large volumes of sand which is important for the coastal sediment budget. The experiment described in this paper gives an insight into the complex hydrodynamics and sediment transport mechanisms related to onshore ridge-runnel migration. Detailed water free surface elevation, fluid velocity and sediment transport rate measurements were taken in a mobile bed wave flume with a focus on the effect of water ponding and runnel drainage on the profile evolution. The measured results have been used to calibrate the time-averaged numerical cross-shore model CSHORE. The model has the capability to deal with the effect of a pronounced profile depression (water-filled runnel) forming on the intermittently wet and dry zone of the beach. Results of the experiment compared with the corresponding numerical model computations show that the rapid onshore migration of a ridge-runnel system under fairly energetic wave conditions can be computed with CSHORE but further improvements of the model are necessary.

scholarly journals NUMERICAL AND EXPERIMENTAL STUDY OF DAM-BREAK FLOOD PROPAGATION AND ITS IMPLICATION TO SEDIMENT EROSION

2012 ◽  
Vol 1 (33) ◽  
pp. 7
Author(s):  
Hung-Chu Hsu ◽  
A. Torres-Freyermuth ◽  
Tian-Jian Hsu ◽  
Hwung-Hweng Hwung
Keyword(s):  
Free Surface ◽  
Sediment Transport ◽  
Numerical Model ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Transport Processes ◽  
Dam Break ◽  
Navier Stokes ◽  
Suspended Sediment Transport ◽  
Initial Stage

Regarding the hydrodynamics, within the past two decades it has become popular in numerical modeling of free-surface flow to adopt a Reynolds-averaged Navier-Stokes approach, where the volume of fluid (VOF) method is utilized to track the evolution of free-surface. However, this robust numerical model has not been widely applied to the study of sediment transport processes. In this study, we shall extend the numerical model to simulate suspended sediment transport and study the erosion pattern during the initial stage of the dam break flow. We also conducted a series of experiments in a horizontal channel of rectangular section and recorded the snap shots of surface profiles of a dam- break wave during the initial stage of dam-break. Measured data is utilized here to study the hydrodynamics and to validate the numerical model.

scholarly journals TOWARDS MODELLING COASTAL SEDIMENT TRANSPORT

1988 ◽  
Vol 1 (21) ◽  
pp. 144 ◽  
Author(s):  
Peter Nielsen
Keyword(s):  
Grain Size ◽  
Sediment Transport ◽  
Littoral Drift ◽  
Transport Models ◽  
Wave Flume ◽  
Oscillatory Velocity ◽  
Waves And Currents ◽  
Coastal Sediment Transport ◽  
Normal Transport ◽  
Insight Into

Sediment transport data from the field and laboratory tests are used to gain insight into two fundamental questions. Firstly: What is the relative importance of coexisting waves and currents for the resulting sediment transport? Secondly: Is the influence of grain size as strong as traditional models predict, or is it as weak as the empirical CERC-formula indicates? Wave tank data reveal that the oscillatory velocity will in most cases determine the direction as well as the magnitude of the shore normal sediment transport, and wave flume data on shore normal transport as well as field data on littoral drift show weaker grain size dependance than traditional sediment transport models predict. It is suggested that wave dominance as well as weak grain size dependence are manifestations of the fact that the dominant transport mechanisms are often more organised than the diffusion process on which many traditional models are based.

scholarly journals Numerical Modelling of the Nearfield Longitudinal Wake Profiles of a High-Speed Prismatic Planing Hull

2020 ◽  
Vol 8 (7) ◽  
pp. 516
Author(s):  
Angus Gray-Stephens ◽  
Tahsin Tezdogan ◽  
Sandy Day
Keyword(s):  
Fluid Dynamics ◽  
Free Surface ◽  
High Speed ◽  
Experimental Testing ◽  
Quantitative Comparison ◽  
Robust Method ◽  
Free Surface Elevation ◽  
Qualitative Comparison ◽  
Computational Fluid Dynamics Cfd ◽  
Insight Into

This study investigates the level of accuracy with which Computational Fluid Dynamics (CFD) is capable of modelling the nearfield longitudinal wake profiles of a high-speed planing hull. It also looks to establish how various set-ups influence the accuracy, with a specific emphasis on turbulence modelling. It analyses a hull over a broad range of conditions to provide detailed insight into the strengths and limitations of CFD, comparing the numerical results to the experimental results previously generated by the authors. A quantitative comparison is made for the centreline (CL) and quarterbeam (QB) longitudinal wake profile plots. Following this, a qualitative comparison is made between photos of the flow pattern from the experimental testing and free surface elevation plots from CFD. The study concluded that CFD is an accurate and robust method of modelling the nearfield longitudinal wake profiles of a high-speed planning hull.

scholarly journals MODELING SHEET FLOW UNDER BREAKING WAVES ON A SURF ZONE SANDBAR

2018 ◽  
pp. 58
Author(s):  
Yeulwoo Kim ◽  
Ryan C. Mieras ◽  
Zhen Cheng ◽  
Tian-Jian Hsu ◽  
Jack A. Puleo
Keyword(s):  
Boundary Layer ◽  
Free Surface ◽  
Sediment Transport ◽  
Numerical Model ◽  
Wave Breaking ◽  
Surf Zone ◽  
Free Stream ◽  
Breaking Waves ◽  
Bottom Boundary Layer ◽  
Horizontal Pressure

Wave-driven sediment transport is one of the main drivers of beach morphodynamics. However, the creation of a comprehensive numerical model remains to be a challenging task due to complex mechanisms associated with unsteadiness and free-surface effects. Particularly for highly non-linear and skewed-asymmetric breaking waves, the boundary layer approximation (i.e., assuming horizontal pressure gradient is equal to local free-stream acceleration) is questionable. Moreover, wave-breaking-induced turbulence may approach the bed and further enhance sediment transport. Thus, a numerical model that can resolve the entire water column from the bottom boundary layer to the free-surface can be a powerful tool to understand wave-driven sediment transport.

LABORATORY EXPERIMENTS ABOUT BED PATTERNS IN THE SHOALING REGION UNDER REGULAR WAVES AND REFLECTING CONDITIONS

2017 ◽  
pp. 25
Author(s):  
Manuel Cobos ◽  
María Clavero ◽  
Sandro Longo ◽  
Asunción Baquerizo ◽  
Miguel Angel Losada
Keyword(s):  
Experimental Study ◽  
Free Surface ◽  
Sediment Transport ◽  
Laboratory Experiments ◽  
Breaking Waves ◽  
Spatial Modulation ◽  
Small Scale ◽  
Growth Mechanisms ◽  
Free Surface Elevation ◽  
Regular Waves

This research is an experimental study of ripple dynamic for regular waves propagating on horizontal and sloping beds in mid- and high-reflective conditions. Small-scale laboratory experiments were carried out on shoaling region (with non breaking waves) and sediment transport in bedload regime. Our experiments showed the key role that plays the reflection in ripple development. The spatial modulation of the free surface elevation due to reflection created sandbars. Ripples grew up in the region where sandbars were appearing. These patterns were gradually reproduced from breakwater to offshore. The incidence of sandbar created a bi-modal structure of ripple geometry. The larger ripples appeared in the crest of sandbars whereas smaller ripples were found in the troughs. Furthermore, it was found that the evolution of ripples at these two locations can be explained by means of different growth mechanisms. Finally, at equilibrium stages, ripple height converges reaching the same height along the sandbar while ripple length and steepness remains almost constant.

An implicit scheme for simulation of free surface non-Newtonian fluid flows on dynamically adapted grids

2021 ◽  
Vol 36 (3) ◽  
pp. 165-176
Author(s):  
Kirill Nikitin ◽  
Yuri Vassilevski ◽  
Ruslan Yanbarisov
Keyword(s):  
Free Surface ◽  
Numerical Model ◽  
Newtonian Fluid ◽  
Viscoelastic Fluid ◽  
Fluid Flows ◽  
Numerical Results ◽  
Implicit Scheme ◽  
New Approach

Abstract This work presents a new approach to modelling of free surface non-Newtonian (viscoplastic or viscoelastic) fluid flows on dynamically adapted octree grids. The numerical model is based on the implicit formulation and the staggered location of governing variables. We verify our model by comparing simulations with experimental and numerical results known from the literature.

Three-dimensional numerical model for open-channels with free-surface variations

2003 ◽  
Vol 41 (1) ◽  
pp. 110-112
Author(s):  
ZhixiaN. Cao ◽  
Rodney Day ◽  
Sarah Liriano
Keyword(s):  
Free Surface ◽  
Numerical Model ◽  
Three Dimensional ◽  
Open Channels

Numerical Investigation of Focused Waves and Their Interaction With a Vertical Cylinder Using REEF3D

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Hans Bihs ◽  
Mayilvahanan Alagan Chella ◽  
Arun Kamath ◽  
Øivind Asgeir Arntsen
Keyword(s):  
Free Surface ◽  
Stokes Equations ◽  
Free Surface Flows ◽  
Surface Elevation ◽  
Numerical Wave Tank ◽  
Free Surface Elevation ◽  
Wave Tank ◽  
Numerical Wave ◽  
Focused Wave ◽  
The Impact

For the stability of offshore structures, such as offshore wind foundations, extreme wave conditions need to be taken into account. Waves from extreme events are critical from the design perspective. In a numerical wave tank, extreme waves can be modeled using focused waves. Here, linear waves are generated from a wave spectrum. The wave crests of the generated waves coincide at a preselected location and time. Focused wave generation is implemented in the numerical wave tank module of REEF3D, which has been extensively and successfully tested for various wave hydrodynamics and wave–structure interaction problems in particular and for free surface flows in general. The open-source computational fluid dynamics (CFD) code REEF3D solves the three-dimensional Navier–Stokes equations on a staggered Cartesian grid. Higher order numerical schemes are used for time and spatial discretization. For the interface capturing, the level set method is selected. In order to test the generated waves, the time series of the free surface elevation are compared with experimental benchmark cases. The numerically simulated free surface elevation shows good agreement with experimental data. In further computations, the impact of the focused waves on a vertical circular cylinder is investigated. A breaking focused wave is simulated and the associated kinematics is investigated. Free surface flow features during the interaction of nonbreaking focused waves with a cylinder and during the breaking process of a focused wave are also investigated along with the numerically captured free surface.

Modelling river bank erosion using a 2D depth-averaged numerical model of flow and non-cohesive, non-uniform sediment transport

2016 ◽  
Vol 93 ◽  
pp. 75-88 ◽  
Author(s):  
Kamal El Kadi Abderrezzak ◽  
Andrés Die Moran ◽  
Pablo Tassi ◽  
Riadh Ata ◽  
Jean-Michel Hervouet
Keyword(s):  
Sediment Transport ◽  
Numerical Model ◽  
Bank Erosion ◽  
River Bank ◽  
River Bank Erosion
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