scholarly journals 2D LARGE-EDDY SIMULATION OF WATER-WAVE IMPACT DURING VIOLENT OVERTOPPING EVENTS

2011 ◽  
Vol 1 (32) ◽  
pp. 16
Author(s):  
Xin Lu ◽  
Qingping Zou ◽  
Dominic E Reeve
Keyword(s):  
Numerical Modeling ◽  
Water Wave ◽  
Breaking Wave ◽  
Wave Impact ◽  
Wave Condition ◽  
Qualitative And Quantitative ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Quantitative Understanding ◽  
The Waves

In this work a newly developed numerical model was employed to conduct comprehensive numerical modeling to investigate the waves overtopping at a vertical seawall, and the associated impact pressures with a certain breaking wave condition. The objective is to qualitative and quantitative understanding of individual violent wave overtopping events on seawalls.

Numerical Study of the Wave Impact on a Square Column Using Large Eddy Simulation

2007 ◽  
Author(s):  
H. T. C. Pedro ◽  
K.-W. Leung ◽  
M. H. Kobayashi ◽  
H. R. Riggs
Keyword(s):  
Numerical Study ◽  
Turbulence Models ◽  
Simple Algorithm ◽  
Navier Stokes ◽  
Wave Impact ◽  
Eddy Simulation ◽  
Subgrid Model ◽  
Large Eddy ◽  
Volume Approximation ◽  
The Impact

This work concerns the numerical investigation of the impact of a wave on a square column. The wave is generated by a dam break in a wave tank. Two turbulence models were used: Large Eddy Simulations (LES) and Unsteady Reynolds Averaged Navier-Stokes (URANS). The numerical simulations were carried out using a finite volume approximation and the SIMPLE algorithm for the solution of the governing equations. Turbulence was modeled with the standard Smagorinsky-Lilly subgrid-model for the LES and the standard κ-ε model for the URANS. The results are validated against experimental data for the wave impact on a square column facing the flow. The results, especially for LES, show very good agreement between the predictions and experimental results. The overall accuracy of the LES, as expected, is superior to the URANS. However, if computational resources are limited, URANS can still provide satisfactory results for structural design.

Large Eddy Simulation of a Swirl-Stabilized Flame

2013 ◽  
Author(s):  
Cheng Zhang ◽  
Wei Zhao
Keyword(s):  
Experimental Data ◽  
Numerical Modeling ◽  
Large Eddy Simulation ◽  
Source Term ◽  
Flow Instabilities ◽  
Filtered Density Function ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Burner Flame ◽  
Mass Fractions

Swirl is used in a wide range of combustions systems such as engines, furnaces, gasifiers, and boilers, to enhance mixing, stabilize flames, and reduce pollutant emissions. Numerical modeling of swirling flows remains a challenging task, since there may exist complex recirculating flow patterns and flow instabilities associated with vortex breakdown, precessing vortex core, and jet precession. In swirling flames, the situation becomes more complex because the unsteady heat release can add other modes of instability. The origins and nature of these instabilities are still not well understood despite many experimental and numerical studies have been conducted in the area. The Sydney swirl burner flame series provide an excellent platform for validating numerical methods for turbulence-chemistry interactions and have been target flames for the TNF workshop series. The burner has well-defined boundary conditions and comprehensive experimental data sets have been documented for different fuel compositions and flow conditions. Compared with the piloted and bluff-body stabilized flames, swirl-stabilized flames pose an additional challenge to numerical modeling because of the complex flow patterns and inherent flow instabilities. In this study, a large eddy simulation (LES)-based multi-environment turbulent combustion model is used to model the Sydney swirl burner flame SMH1. The multi-environment filtered density function model (MEFDF) depicts the filtered density function (FDF) as a weighted summation of a small number of multi-dimensional Dirac delta functions in composition space. It is derived from the transport FDF equation using the direct quadrature method of moments (DQMOM). The MEFDF method with multiple reactive scalars retains the unique property of the joint FDF model of treating the chemical source term exactly. A 19-species mechanism reduced from GRI-Mech 2.11 is employed for chemical kinetics. The in situ adaptive tabulation algorithm (ISAT) is used to speed-up the evaluation of the chemical source term. The predicted radial profiles of the axial velocity, azimuthal velocity, mixture fraction, temperature, and species mass fractions of CO2, CO, and NO are in reasonable agreement with the experimental data. It has been found that, compared with the experimental data, the profiles of the temperature and species mass fractions shifted slightly outward in the radial direction at downstream locations and NO mass fraction is slightly over-predicted at most locations. Further work will be needed to find out possible reasons for these discrepancies.

Numerical Modeling of Bed Profile Evolution Using Large Eddy Simulation

2013 ◽  
Vol 65 ◽  
pp. 350-355 ◽  
Author(s):  
M.A.C. Niroshinie ◽  
Takayuki Suzuki ◽  
Jun Sasaki
Keyword(s):  
Numerical Modeling ◽  
Large Eddy Simulation ◽  
Eddy Simulation ◽  
Large Eddy

scholarly journals Effects of Geometry and Hydraulic Characteristics of Shallow Reservoirs on Sediment Entrapment

Water ◽  
2018 ◽  
Vol 10 (12) ◽  
pp. 1725 ◽  
Author(s):  
Hamidreza Zahabi ◽  
Mohammadamin Torabi ◽  
Ebrahim Alamatian ◽  
Mehdi Bahiraei ◽  
Marjan Goodarzi
Keyword(s):  
Numerical Modeling ◽  
Software Package ◽  
Reasonable Agreement ◽  
Numerical Data ◽  
Considerable Effect ◽  
Hydraulic Characteristics ◽  
Eddy Simulation ◽  
Large Eddy ◽  
3D Software ◽  
Shallow Reservoirs

Sediment and deposition are among the main problems in dam engineering and other related fields. Because of the numerous advantages of numerical modeling, effects of different geometries of reservoirs on the flow pattern and deposition of sediments are investigated using the finite volume based Flow-3D software package. In this study, three rectangular reservoirs with different dimensional ratios are simulated using the large eddy simulation (LES) turbulence model. To validate the numerical modeling, existing experimental data is used. Results indicate that Flow-3D can accurately simulate flow and sediment deposition in the reservoirs, and the numerical data are in reasonable agreement with the experimental results. Numerical efforts showed that the amount of deposition in reservoirs is significantly dependent on the geometry. Among the modeled reservoirs, the 6 × 4 m one has the best performance. Moreover, it can be said that changing the position of the flow’s inlet and outlet of the reservoir does not have a considerable effect on increasing its efficiency.

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.

Dynamic modelling of sea-surface roughness for large-eddy simulation of wind over ocean wavefield

2013 ◽  
Vol 726 ◽  
pp. 62-99 ◽  
Author(s):  
Di Yang ◽  
Charles Meneveau ◽  
Lian Shen
Keyword(s):  
Surface Roughness ◽  
Large Eddy Simulation ◽  
Wind Wave ◽  
Dynamic Modelling ◽  
Sea Surface ◽  
Near Surface ◽  
Eddy Simulation ◽  
Sea Surface Roughness ◽  
Large Eddy ◽  
The Waves

AbstractWind blowing over the ocean surface can be treated as a turbulent boundary layer over a multiscale rough surface with moving roughness elements, the waves. Large-eddy simulation (LES) of such flows is challenging because LES resolves wind–wave interactions only down to the grid scale, $\Delta $, while the effects of subgrid-scale (SGS) waves on the wind need to be modelled. Usually, a surface-layer model based on the law of the wall is used; but the surface roughness has been known to depend on the local wind and wave conditions and is difficult to parameterize. In this study, a dynamic model for the SGS sea-surface roughness is developed, with the roughness corresponding to the SGS waves expressed as ${\alpha }_{w} \hspace{0.167em} { \sigma }_{\eta }^{\Delta } $. Here, ${ \sigma }_{\eta }^{\Delta } $ is the effective amplitude of the SGS waves, modelled as a weighted integral of the SGS wave spectrum based on the geometric and kinematic properties of the waves for which five candidate expressions are examined. Moreover, ${\alpha }_{w} $ is an unknown dimensionless model coefficient determined dynamically based on the first-principles constraint that the total surface drag force or average surface stress must be independent of the LES filter scale $\Delta $. The feasibility and consistency of the dynamic sea-surface roughness models are assessed by a priori tests using data from high-resolution LES with near-surface resolution, appropriately filtered. Also, these data are used for a posteriori tests of the dynamic sea-surface roughness models in LES with near-surface modelling. It is found that the dynamic modelling approach can successfully capture the effects of SGS waves on the wind turbulence without ad hoc prescription of the model parameter ${\alpha }_{w} $. Also, for ${ \sigma }_{\eta }^{\Delta } $, a model based on the kinematics of wind–wave relative motion achieves the best performance among the five candidate models.

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