A Nonlinear Three-Dimensional Coupled Fluid-Sediment Interaction Model for Large Seabed Deformation

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Tomoaki Nakamura ◽  
Solomon C. Yim
Keyword(s):  
Sediment Transport ◽  
Three Dimensional ◽  
Interaction Model ◽  
Navier Stokes ◽  
Coupling Scheme ◽  
Model Parameters ◽  
Interface Tracking ◽  
Beach Profile ◽  
Time Step ◽  
Profile Change

A nonlinear three-dimensional two-way coupled fluid-sediment interaction model is developed in this study. The model is composed of a generalized Navier–Stokes solver (GNS) with a volume of fluid module for air-water interface tracking and a sediment transport module (STM) for fluid-sediment interface tracking. The GNS model is based on the finite difference method with a turbulent stress model of large-eddy simulation to compute incompressible viscous multiphase flows. The STM is used to compute nonlinear sediment bed profile change due to bed-load sediment transport. A two-way coupling scheme connecting GNS with STM is implemented at each time step to ensure the fluid-sediment interaction. For validation, the fluid-sediment interaction model is applied to predict cross-shore profile change of a sloping beach due to breaking solitary waves, and the resulting predictions are examined and compared with the measured data from a set of hydraulic tests. It is found that the fluid-sediment interaction model predicts reasonably well the sediment transport and the resulting beach profile change. The sensitivity of model parameters involving the sediment transport to the beach profile change is analyzed. Finally, the fluid-sediment interaction model is applied to predict local scour in front of a quay wall due to a jet flow to demonstrate its applicability to general three-dimensional problems.

scholarly journals THREE-DIMENSIONAL NUMERICAL ANALYSIS ON DEFORMATION OF RUN-UP TSUNAMI AND TSUNAMI FORCE ACTING ON SQUARE STRUCTURES

2011 ◽  
Vol 1 (32) ◽  
pp. 14 ◽  
Author(s):  
Tomoaki Nakamura ◽  
Norimi Mizutani ◽  
Koji Fujima
Keyword(s):  
Three Dimensional ◽  
Interaction Model ◽  
Navier Stokes ◽  
Interface Tracking ◽  
Time Step ◽  
Porous Flow ◽  
Inundation Depth ◽  
Coupling Procedure ◽  
Run Up ◽  
Tsunami Run Up

A three-dimensional two-way coupled fluid-sediment interaction model (FSM) is applied to investigate run-up tsunami deformation and tsunami force acting on square structures on land. The FSM consists of a generalized Navier-Stokes solver (GNS) for multi-phase flow including porous flow, a volume of fluid module (VFM) for air-water interface tracking, and a sediment transport module (STM) for fluid-sediment interface tracking. In the FSM, a two-way coupling procedure is implemented at each time step to connect the GNS with the VFM and the STM. The predictive capability of the FSM is demonstrated through comparison between numerical results and experimental data in terms of water surface elevation, inundation depth, and tsunami force. The process of tsunami run-up in the presence of square structures is investigated in terms of vortex structures. The result shows that the FSM is a useful tool providing detailed information in discussing run-up tsunami deformation and tsunami force.

Database of Sail Shapes vs. Sail Performance and Validation of Numerical Calculation for Upwind Condition

2007 ◽  
Author(s):  
Yutaka Masuyama ◽  
Yusuke Tahara ◽  
Toichi Fukasawa ◽  
Naotoshi Maeda
Keyword(s):  
Numerical Method ◽  
Vortex Lattice ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Numerical Calculations ◽  
Navier Stokes ◽  
Coupling Scheme ◽  
Aerodynamic Coefficients ◽  
Lattice Method ◽  
Cfd Method

Database of full-scale three-dimensional sail shapes are presented with the aerodynamic coefficients for the upwind condition of IMS type sails. Three-dimensional shape data are used for the input of numerical calculations and the results are compared with the measured sail performance. The sail shapes and performance are measured using a sail dynamometer boat Fujin. The Fujin is a 34-foot LOA boat, in which load cells and charge coupled devices (CCD) cameras are installed to measure the sail forces and shapes simultaneously. The sailing conditions of the boat, such as boat speed, heel angle, wind speed, wind angle, and so on, are also measured. The tested sail configurations are as follows: mainsail with 130% jib, mainsail with 75% jib and mainsail alone. Sail shapes are measured at several height positions. The measured shape parameters are chord length, maximum draft, maximum draft position, entry angle at the luff and exit angle at the leech. From these parameters three-dimensional coordinates of the sails are calculated by interpolation. These three-dimensional coordinates are tabulated with the aerodynamic coefficients. Numerical calculations are performed using the measured sail shapes. The calculation methods are of two types; Reynolds-averaged Navier-Stokes (RANS)-based CFD and vortex lattice methods (VLM). A multi-block RANS-based CFD method was developed by one of the authors and is capable of predicting viscous flows and aerodynamic forces for complicated sail configuration for upwind as well as downwind conditions. Important features of the numerical method are summarized as follows: a Finite- Analytic scheme to discretize transport equations, a PISO type velocity-pressure coupling scheme, multi-block domain decomposition capability, and several choices of turbulence models depending on flows of interest. An automatic grid generation scheme is also included. Another calculation method, the vortex lattice method is also adopted. In this case, step-by-step calculations are conducted to attain the steady state of the sail in steady wind. Wake vortices are generated step-by-step, which flow in the direction of the local velocity vector. These calculated sail forces are compared with the measured one, and the validity of the numerical method is studied. The sail shape database and comparison with numerical calculations will provide a good benchmark for the sail performance analysis of the upwind condition of IMS type sails.

Numerical integration of the three-dimensional Navier-Stokes equations for incompressible flow

1969 ◽  
Vol 37 (4) ◽  
pp. 727-750 ◽  
Author(s):  
Gareth P. Williams
Keyword(s):  
Poisson Equation ◽  
Incompressible Flows ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Wave Flow ◽  
Trigonometric Interpolation ◽  
Time Step ◽  
Navier Stokes Equations ◽  
The Poisson Equation

A method of numerically integrating the Navier-Stokes equations for certain three-dimensional incompressible flows is described. The technique is presented through application to the particular problem of describing thermal convection in a rotating annulus. The equations, in cylindrical polar co-ordinate form, are integrated with respect to time by a marching process, together with the solving of a Poisson equation for the pressure. A suitable form of the finite difference equations gives a computationally-stable long-term integration with reasonably faithful representation of the spatial and temporal characteristics of the flow.Trigonometric interpolation techniques provide accurate (discretely exact) solutions to the Poisson equation. By using an auxiliary algorithm for rapid evaluation of trigonometric transforms, the proportion of computation needed to solve the Poisson equation can be reduced to less than 25% of the total time needed to’ advance one time step. Computing on a UNIVAC 1108 machine, the flow can be advanced one time-step in 2 sec for a 14 × 14 × 14 grid upward to 96 sec for a 60 × 34 × 34 grid.As an example of the method, some features of a solution for steady wave flow in annulus convection are presented. The resemblance of this flow to the classical Eady wave is noted.

scholarly journals Three-Dimensional Simulation of Fluid–Structure Interaction Problems Using Monolithic Semi-Implicit Algorithm

Fluids ◽  
2019 ◽  
Vol 4 (2) ◽  
pp. 94 ◽  
Author(s):  
Cornel Marius Murea
Keyword(s):  
Stokes Equations ◽  
Fluid Structure Interaction ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Arbitrary Lagrangian Eulerian ◽  
Time Step ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Dimensional Simulation ◽  
Updated Lagrangian

A monolithic semi-implicit method is presented for three-dimensional simulation of fluid–structure interaction problems. The updated Lagrangian framework is used for the structure modeled by linear elasticity equation and, for the fluid governed by the Navier–Stokes equations, we employ the Arbitrary Lagrangian Eulerian method. We use a global mesh for the fluid–structure domain where the fluid–structure interface is an interior boundary. The continuity of velocity at the interface is automatically satisfied by using globally continuous finite element for the velocity in the fluid–structure mesh. The method is fast because we solve only a linear system at each time step. Three-dimensional numerical tests are presented.

Numerical modelling of cohesive sediment transport in rivers

2004 ◽  
Vol 31 (5) ◽  
pp. 749-758 ◽  
Author(s):  
David H Willis ◽  
B G Krishnappan
Keyword(s):  
Sediment Transport ◽  
Three Dimensional ◽  
Cohesive Sediment ◽  
Low Flow ◽  
Shear Stresses ◽  
Hydrodynamic Models ◽  
Coupled Models ◽  
Time Step ◽  
Water And Sediment ◽  
Sediment Model

Techniques available to practicing civil engineers for numerically modelling cohesive mud in rivers and estuaries are reviewed. Coupled models, treating water and sediment as a single process, remain research tools but are usually not three-dimensional. The decoupled approach, which separates water and sediment computations at each model time step, allows the three-dimensional representation of at least the bed and the use of well-proven, commercial, numerical, hydrodynamic models. Most hydrodynamic models compute sediment transport in suspension but may require modification of the dispersion coefficients to account for the presence of sediment. The sediment model deals with the sediment exchange between the water column and the bed using existing equations for erosion and deposition. Both equations relate the sediment exchange rates to the shear stress in the bottom boundary layer. In real rivers and estuaries, a depositional bed layer is associated with a period of low flow and shear, at slack tide for example, whereas in numerical models a layer is defined by the model time step. The sediment model keeps track of the uppermost layers at each model grid point, including consolidation and strengthening. Although numerical hydrodynamic models are based strongly on physics, sediment models are only numerical frameworks for interpolating and extrapolating full-scale field or laboratory measurements of "hydraulic sediment parameters," such as threshold shear stresses. Calibration and verification of models against measurement are therefore of prime importance.Key words: cohesive sediment, mathematical modelling, settling velocity, erosion, resuspension, deposition, fluid mud, bed layers.

A RANS numerical model for cross-shore beach profile evolution

2020 ◽  
Author(s):  
Julio Garcia-Maribona ◽  
Javier L. Lara ◽  
Maria Maza ◽  
Iñigo J. Losada
Keyword(s):  
Sediment Transport ◽  
Numerical Model ◽  
Transport Model ◽  
Numerical Models ◽  
Computational Cost ◽  
Physical Modelling ◽  
Computational Effort ◽  
Beach Profile ◽  
Time Step ◽  
Wave Conditions

<p>The evolution of the cross-shore beach profile is tightly related to the evolution of the coastline in both small and large time scales. Bathymetry changes in extreme maritime events can also have important effects on coastal infrastructures such as geotechnical failures of foundations or the modification of the incident wave conditions towards a more unfavourable situation.</p><p>The available strategies to study the evolution of beach profiles can be classified in analytical, physical and numerical modelling. Analytical solutions are fast, but too simplistic for many applications. Physical modelling provides trustworthy results and can be applied to a wide variety of configurations, however, they are costly and time-consuming compared to analytical strategies. Finally,  numerical approaches offer different balances between cost and precision depending on the particular model.</p><p>Some numerical models provide greater precision in the beach profile evolution, but incurring in a prohibitive computational cost for many applications. In contrast, the less expensive ones assume simplifications which do not allow to correctly reproduce significant phenomena of the near-shore hydrodynamics such as wave breaking or undertow currents, neither to predict important features of the beach profile like breaker bars.</p><p>In this work, a new numerical model is developed to reproduce the main features of the beach profile and hydrodynamics while maintaining an affordable computational cost. In addition, it is intended to reduce to the minimum the number of coefficients that the user has to provide to make the model more predictive.</p><p>The model consists of two main modules. Firstly, the already existing 2D RANS numerical model IH2VOF is used to compute the hydrodynamics. Secondly, the sediment transport model modifies the bathymetry according to the obtained hydrodynamics. The new bathymetry is then considered in the hydrodynamic model to account for it in the next time step.</p><p>The sediment transport module considers bedload and suspended transports separately. The former is obtained with empirical formulae. In the later,the distribution of sediment concentration in the domain is obtained by solving an advective-diffusive transport equation. Then, the sedimentation and erosion rates are obtained along the seabed.<br>Once these contributions are calculated, a sediment balance is performed in every seabed segment to determine the variation in its level.</p><p>With the previously described strategy, the resulting model is able to predict not only the seabed changes due to different wave conditions, but also the influence of this new bathymetry in the hydrodynamics, capturing features such as the generation of a breaker bar, displacement of the breaking point or variation of the run-up over the beach profile. To validate the model, the numerical results are compared to experimental data.</p><p>An important novelty of the present model is the computational effort required to perform the simulations, which is significantly smaller than the one associated to existing models able to reproduce the same phenomena.</p>

Numerical Solution of Incompressible Unsteady Flows in Turbomachinery

2000 ◽  
Vol 123 (3) ◽  
pp. 680-685 ◽  
Author(s):  
L. He ◽  
K. Sato
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Unsteady Flows ◽  
Navier Stokes ◽  
Time Step ◽  
Navier Stokes Equations ◽  
Flow Solver ◽  
Time Stepping ◽  
Incompressible Viscous Flow ◽  
Dual Time Stepping

A three-dimensional incompressible viscous flow solver of the thin-layer Navier-Stokes equations was developed for the unsteady turbomachinery flow computations. The solution algorithm for the unsteady flows combines the dual time stepping technique with the artificial compressibility approach for solving the incompressible unsteady flow governing equations. For time accurate calculations, subiterations are introduced by marching the equations in the pseudo-time to fully recover the incompressible continuity equation at each real time step, accelerated with a multi-grid technique. Computations of test cases show satisfactory agreements with corresponding theoretical and experimental results, demonstrating the validity and applicability of the present method to unsteady incompressible turbomachinery flows.

Off-Road Vehicle Dynamics Mobility Simulation With a Compaction Based Deformable Terrain Model

2013 ◽  
Author(s):  
Justin Madsen ◽  
Andrew Seidl ◽  
Dan Negrut
Keyword(s):  
Vehicle Dynamics ◽  
Transfer Functions ◽  
Soil Mechanics ◽  
Three Dimensional ◽  
Interaction Model ◽  
Simulation Software ◽  
Repeated Loading ◽  
Model Parameters ◽  
Vehicle Simulation ◽  
Terrain Model

This paper discusses the terramechanics models developed to incorporate a physics-based, three dimensional deformable terrain database model with vehicle dynamics mobility simulation software. The vehicle model is contained in Chrono, a research-grade C++ based Application Programming Interface (API) that enables accurate multibody simulations. The terrain database is also contained in a C++ based API, and includes a general tire-terrain interaction model which is modular to allow for any tire model that supports the Standard Tire Interface (STI) to operate on the terrain. Furthermore, the ability to handle arbitrary, three dimensional traction element geometry allows for tracked vehicles (or vehicle hulls) to also interact with the deformable terrain. The governing equations of the terrain are based on a soil compaction model that includes both the propagation of subsoil stresses due to vehicular loads, and the resulting visco-elastic-plastic stress/strain on the affected soil volume. Non-flat, non-homogenous and non-uniform soil densities, rutting, repeated loading and strain hardening effects are all captured in the vehicle mobility response as a result of the general 3-D tire/terrain model developed. Pedo-transfer functions allow for the calculation of the soil mechanics model parameters from existing soil measurements. This terrain model runs at near real-time speed, due to parallel CPU and GPU implementation. Results that exercise the force models developed with the 3-D tire geometry are presented and discussed for a kinematically driven tire and a full vehicle simulation.

Application of an Improved Streamline Curvature Approach to a Modern, Two-Stage Transonic Fan: Comparison With Data and CFD

2002 ◽  
Author(s):  
Keith M. Boyer ◽  
Walter F. O’Brien
Keyword(s):  
Three Dimensional ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Model Parameters ◽  
Two Stage ◽  
Streamline Curvature ◽  
Wide Range ◽  
Improved Model ◽  
Transonic Fan ◽  
Streamline Curvature Method

A streamline curvature method with improvements to key loss models is applied to a two-stage, low aspect ratio, transonic fan with design tip relative Mach number of approximately 1.65. Central to the improvements is the incorporation of a physics-based shock model. The attempt here is to capture the effects of key flow phenomena relative to the off-design performance of the fan. A quantitative analysis regarding solution sensitivities to model parameters that influence the key phenomena over a wide range of operating conditions is presented. Predictions are compared to performance determined from overall and interstage measurements, as well as from a three-dimensional, steady, Reynolds-averaged Navier-Stokes method applied across the first rotor. Overall and spanwise comparisons demonstrate that the improved model gives reasonable performance trending and generally accurate results. The method can be used to provide boundary conditions to higher-order solvers, or implemented within novel approaches using the streamline curvature method to explore complex engine-inlet integration issues, such as time-variant distortion.

Strongly Coupled Fluid-Structure Interactions via a New Navier-Stokes Method for Prediction of Vortex-Induced Vibrations

2005 ◽  
Author(s):  
Yannis Kallinderis ◽  
Hyung Taek Ahn
Keyword(s):  
Stokes Equations ◽  
Computational Cost ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Design Tool ◽  
Navier Stokes ◽  
Time Step ◽  
Navier Stokes Equations ◽  
Vortex Induced Vibrations ◽  
Offshore Industry

Numerical prediction of vortex-induced vibrations requires employment of the unsteady Navier-Stokes equations. Current Navier-Stokes solvers are quite expensive for three-dimensional flow-structure applications. Acceptance of Computational Fluid Dynamics as a design tool for the offshore industry requires improvements to current CFD methods in order to address the following important issues: (i) stability and computation cost of the numerical simulation process, (ii) restriction on the size of the allowable time-step due to the coupling of the flow and structure solution processes, (iii) excessive number of computational elements for 3-D applications, and (iv) accuracy and computational cost of turbulence models used for high Reynolds number flow. The above four problems are addressed via a new numerical method which employs strong coupling between the flow and the structure solutions. Special coupling is also employed between the Reynolds-averaged Navier-Stokes equations and the Spalart-Allmaras turbulence model. An element-type independent spatial discretization scheme is also presented which can handle general hybrid meshes consisting of hexahedra, prisms, pyramids, and tetrahedral.

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