scholarly journals Unstructured Finite-Volume Model of Sediment Scouring Due to Wave Impact on Vertical Seawalls

2021 ◽  
Vol 9 (12) ◽  
pp. 1440
Author(s):  
Miguel Uh Zapata ◽  
Damien Pham Van Bang ◽  
Kim Dan Nguyen
Keyword(s):  
Numerical Modeling ◽  
Finite Volume ◽  
Three Dimensional ◽  
Wave Structure ◽  
Complex Nature ◽  
Breaking Wave ◽  
Computational Domain ◽  
Wave Impact ◽  
Interface Evolution ◽  
Fully Implicit

The numerical modeling of sediment transport under wave impact is challenging because of the complex nature of the triple wave–structure–sediment interaction. This study presents three-dimensional numerical modeling of sediment scouring due to non-breaking wave impact on a vertical seawall. The Navier–Stokes–Exner equations are approximated to calculate the full evolution of flow fields and morphodynamic responses. The bed erosion model is based on the van Rijn formulation with a mass-conservative sand-slide algorithm. The numerical solution is obtained by using a projection method and a fully implicit second-order unstructured finite-volume method in a σ-coordinate computational domain. This coordinate system is employed to accurately represent the free-surface elevation and sediment/water interface evolution. Experimental results of the velocity field, surface wave motion, and scour hole formation hole are used to compare and demonstrate the proposed numerical method’s capabilities to model the seawall scour.

Reducing Undesired Wave Reflection at Domain Boundaries in 3D Finite Volume-Based Flow Simulations via Forcing Zones

2020 ◽  
Vol 64 (01) ◽  
pp. 23-47
Author(s):  
Robinson Peric ◽  
Moustafa Abdel-Maksoud
Keyword(s):  
Finite Volume ◽  
Wave Reflection ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Special Focus ◽  
Computational Domain ◽  
Wave Reflections ◽  
Flow Simulations ◽  
Large Eddy ◽  
Domain Boundaries

This article reviews different types of forcing zones (sponge layers, damping zones, relaxation zones, etc.) as used in finite volume-based flow simulations to reduce undesired wave reflections at domain boundaries, with special focus on the case of strongly reflecting bodies subjected to long-crested incidence waves. Limitations and possible sources of errors are discussed. A novel forcing-zone arrangement is presented and validated via three-dimensional (3D) flow simulations. Furthermore, a recently published theory for predicting the forcing-zone behavior was investigated with regard to its relevance for practical 3D hydrodynamics problems. It was found that the theory can be used to optimally tune the case-dependent parameters of the forcing zones before running the simulations. 1. Introduction Wave reflections at the boundaries of the computational domain can cause significant errors in flow simulations, and must therefore be reduced. In contrast to boundary element codes, where much progress in this respect has been made decades ago (see e.g., Clement 1996; Grilli &Horillo 1997), for finite volume-based flow solvers, there are many unresolved questions, especially:How to reliably reduce reflections and disturbances from the domain boundaries?How to predict the amount of undesired wave reflection before running the simulation? This work aims to provide further insight to these questions for flow simulations based on Navier-Stokes-type equations (Reynolds-averaged Navier-Stokes, Euler equations, Large Eddy Simulations, etc.), when using forcing zones to reduce undesired reflections. The term "forcing zones" is used here to describe approaches that gradually force the solution in the vicinity of the boundary towards some reference solution, as described in Section 2; some examples are absorbing layers, sponge layers, damping zones, relaxation zones, or the Euler overlay method (Mayer et al. 1998; Park et al. 1999; Chen et al. 2006; Choi &Yoon 2009; Jacobsen et al. 2012; Kimet al. 2012; Schmitt & Elsaesser 2015; Perić & Abdel-Maksoud 2016a; Vukčević et al. 2016).

Spreadsheet Tool for Quick-Turn 3D Numerical Modeling of Package Thermal Performance With Non-Uniform Die Heating

2001 ◽  
Author(s):  
Abhay A. Watwe ◽  
Ravi S. Prasher
Keyword(s):  
Finite Element ◽  
Numerical Modeling ◽  
Finite Volume ◽  
Thermal Performance ◽  
Three Dimensional ◽  
3D Numerical Modeling ◽  
Conventional Analysis ◽  
Time Required ◽  
The Impact ◽  
Fourier Equation

Abstract Traditional methods of estimating package thermal performance employ numerical modeling using commercially available finite-volume or finite-element tools. Use of these tools requires training and experience in thermal modeling. This methodology restricts the ability of die designers to quickly evaluate the thermal impact of their die architecture due to the added throughput time required to enlist the services of a thermal analyst. This paper describes the development of an easy to use spreadsheet tool, which performs quick-turn numerical evaluations of the impact of non-uniform die heating. The tool employs well-established finite-volume numerical techniques to solve the steady-state, three-dimensional Fourier equation of conduction in the package geometry. Minimal input data is required and the inputs are customized using visual basic pull-down menus to assist die designers who may not be thermal experts. Data showing comparison of the estimates from the spreadsheet tool with that obtained from a conventional analysis using the commercially available finite element code ANSYS™ is also presented.

Three-dimensional numerical modeling of cohesive sediment transport and wind wave impact in a shallow oxbow lake

2008 ◽  
Vol 31 (7) ◽  
pp. 1004-1014 ◽  
Author(s):  
Xiaobo Chao ◽  
Yafei Jia ◽  
F. Douglas Shields ◽  
Sam S.Y. Wang ◽  
Charles M. Cooper
Keyword(s):  
Numerical Modeling ◽  
Sediment Transport ◽  
Wind Wave ◽  
Three Dimensional ◽  
Cohesive Sediment ◽  
Oxbow Lake ◽  
Wave Impact ◽  
Cohesive Sediment Transport

On the Validity and Sensitivity of CFD Simulations for a Deterministic Breaking Wave Impact on a Semi Submersible

2018 ◽  
Author(s):  
Henry Bandringa ◽  
Joop A. Helder
Keyword(s):  
Free Surface ◽  
Absorbing Boundary Conditions ◽  
Implicit Time ◽  
Breaking Wave ◽  
Computational Domain ◽  
Wave Impact ◽  
Time Step ◽  
Cfd Simulations ◽  
Detailed Model ◽  
Run Up

To assess the integrity and safety of structures offshore, prediction of run-up, green water, and impact loads needs to be made during the structure’s design. For predicting these highly non-linear phenomena, most of the offshore industry relies on detailed model testing. In the last couple of years however, CFD simulations have shown more and more promising results in predicting these events, see for instance [1]–[4]. To obtain confidence in the accuracy of CFD simulations in the challenging field of extreme wave impacts, a proper validation of such CFD tools is essential. In this paper two CFD tools are considered for the simulation of a deterministic breaking wave impact on a fixed semi submersible, resulting in flow phenomena like wave run-up, horizontal wave impact and deck impacts. Hereby, one of the CFD tools applies an unstructured gridding approach and implicit free-surface reconstruction, and uses an implicit time integration with a fixed time step. The other CFD tool explicitly reconstructs the free surface on a structured grid and integrates the free surface explicitly in time, using a variable time step. The presented simulations use a compact computational domain with wave absorbing boundary conditions and local grid refinement to reduce CPU time. Besides a typical verification and validation of the results, for one of the CFD tools a sensitivity study is performed in which the influence of small variations in the incoming breaking wave on the overall results is assessed. Such an analysis should provide the industry more insight in the to-be-expected sensitivity (and hence uncertainty) of CFD simulations for these type of applications. Experiments carried out by MARIN are used to validate all the presented simulation results.

2D multi-layer hydrodynamic and sediment transport modelling in a tidal estuary

2020 ◽  
Author(s):  
Kai-Yi Bai ◽  
Jiing-Yun You
Keyword(s):  
Sediment Transport ◽  
Shallow Water ◽  
Finite Volume ◽  
Stokes Equations ◽  
Transport Model ◽  
Three Dimensional ◽  
Sediment Concentration ◽  
Computational Domain ◽  
Operation Rules ◽  
Sediment Transport Model

<p>This study developed a multi-layer hydrodynamic and sediment transport model for simulating tides and the estuarine flows. The flow circulation in an estuary shows complicated mixing and stratification patterns due to the combined effects from currents and tides. This kind of issues becomes more important in Taiwan in line with the more and more frequent sediment flushing operation which led to high sediment concentration flow at the estuary. In some applications,  three-dimensional (3D) models solving full Navier-Stokes equations were used. However, the extremely high computational cost, especially for the large-scale environmental problems, is always a serious concern. In the past years, continuous efforts have been devoted to the development of efficient quasi-three-dimensional models under hydrostatic and Boussinesq assumptions. Following the same state-of-the-art modelling strategy, this study develops a multi-layer shallow-water and sediment transport model with finite volume method. In this model, a terrain following coordinate with high local resolution is used to vertically divide the computational domain into multiple layers to better addressing bottom topography and velocity profile. Our model is rigorously validated against several benchmark cases including winddriven circulation, subcritical flow over a hump, tidal wave propagation, and sediment transport. The grid convergence test and accuracy both are in good agreement with analytical solutions. Subsequently, the model is applied to investigate the estuary dynamics and sediment transport under different conditions, e.g., flow discharges, bottom slopes, wind shears and tidal variations. Overall, the results show a relationship between flow conditions and sediment transport. Later, some scenarios for various upstream inflow and sediment concentration will be examined to assess the reservoir operation rules. </p><p><strong>Keywords: shallow water, sediment transport, multi-layer, hydrostatic, Boussinesq Assumption, a finite volume characteristics (FVC) method </strong><br> </p><p><br> <br> <br><br> </p>

scholarly journals Numerical modeling of surface wave development under the action of wind

Ocean Science ◽  
2018 ◽  
Vol 14 (3) ◽  
pp. 453-470 ◽  
Author(s):  
Dmitry Chalikov
Keyword(s):  
Numerical Modeling ◽  
Surface Wave ◽  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Wave Structure ◽  
Two Dimensional ◽  
Transform Method ◽  
Long Time ◽  
Vertical Grid ◽  
Wave Development

Abstract. The numerical modeling of two-dimensional surface wave development under the action of wind is performed. The model is based on three-dimensional equations of potential motion with a free surface written in a surface-following nonorthogonal curvilinear coordinate system in which depth is counted from a moving surface. A three-dimensional Poisson equation for the velocity potential is solved iteratively. A Fourier transform method, a second-order accuracy approximation of vertical derivatives on a stretched vertical grid and fourth-order Runge–Kutta time stepping are used. Both the input energy to waves and dissipation of wave energy are calculated on the basis of earlier developed and validated algorithms. A one-processor version of the model for PC allows us to simulate an evolution of the wave field with thousands of degrees of freedom over thousands of wave periods. A long-time evolution of a two-dimensional wave structure is illustrated by the spectra of wave surface and the input and output of energy.

scholarly journals Numerical modeling of surface wave development under the action of wind

2018 ◽  
Author(s):  
Dmitry Chalikov
Keyword(s):  
Numerical Modeling ◽  
Surface Wave ◽  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Wave Structure ◽  
Two Dimensional ◽  
Transform Method ◽  
Long Time ◽  
Vertical Grid ◽  
Wave Development

Abstract. The numerical modeling of two-dimensional surface wave development under the action of wind is performed. The model is based on three-dimensional equations of potential motion with free surface written in a surface-following non-orthogonal curvilinear coordinate system where depth is counted from moving surface. А three-dimensional Poisson equation for velocity potential is solved iteratively. А Fourier transform method, the second-order accuracy approximation of vertical derivatives on a stretched vertical grid and the fourth-order Runge–Kutta time stepping are used. Both the input energy to waves and dissipation of wave energy are calculated on the basis of the earlier developed and validated algorithms. A one-processor version of the model for PC allows us to simulate an evolution of wave field with thousands degrees of freedom over thousands of wave periods. A long-time evolution of two-dimensional wave structure is illustrated by the spectra of wave surface and input and output of energy.

Application of an All-Speed Implicit Finite-Volume Algorithm to Rayleigh–Taylor Instability

2015 ◽  
Vol 12 (03) ◽  
pp. 1550018 ◽  
Author(s):  
Ilyas Yilmaz ◽  
Firat Oguz Edis ◽  
Hasan Saygin
Keyword(s):  
Mach Number ◽  
Finite Volume ◽  
Turbulent Mixing ◽  
Stokes Equations ◽  
Baroclinic Instability ◽  
Three Dimensional ◽  
Taylor Instability ◽  
Fully Implicit ◽  
Energy Conserving ◽  
Rayleigh Taylor Instability

We present a three-dimensional Direct Numerical Simulation (DNS) study of Rayleigh–Taylor Instability (RTI) using an all-speed, fully implicit, nondissipative and discrete kinetic energy conserving algorithm. In order to perform this study, an in-house, fully parallel, finite-volume, DNS solver, iDNS, which solves the set of time-dependent, compressible Navier–Stokes equations with gravity was developed based on the present algorithm and the PETSc parallel library. It is shown that the algorithm is able to capture the correct physics of the baroclinic instability and turbulent mixing. Compressibility (i.e., high Mach number) has been found more effective on the development of the flow after the diffusive growth phase passed. An increase in bubble growth rate together with a decrease in turbulent mixing was also observed at Mach number 1.1.

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