scholarly journals VOLUME-OF-FLUID MODEL COMFLOW SIMULATIONS OF WAVE IMPACTS ON A DIKE

2011 ◽  
Vol 1 (32) ◽  
pp. 17 ◽  
Author(s):  
Ivo Wenneker ◽  
Peter Wellens ◽  
Reynald Gervelas
Keyword(s):  
Flow Model ◽  
Two Phase Flow ◽  
Stokes Equations ◽  
Pressure Sensors ◽  
Navier Stokes ◽  
Phase Flow ◽  
Grid Cells ◽  
Two Phase ◽  
Navier Stokes Equations ◽  
Cpu Time

ComFLOW is a 3D Volume-of-Fluid (VOF) model to solve the incompressible Navier-Stokes equations including free surface, or to solve the Navier-Stokes equations for two-phase flow problems (two-phase flow: both an incompressible viscous fluid (e.g., water) and a compressible viscous fluid (e.g., air) are present). The problem statement of the present study reads: ‘Is ComFLOW capable of accurate prediction of wave impacts on (impermeable) coastal structures such as dikes? And, if so, what are the preferred model settings and associated computing times?’. In this paper, ComFLOW is validated for this purpose by comparison against pressure data as measured in the Delta flume by pressure sensors at dikes. We have selected three different experiments, with typical dike geometries (slope 1:3.5, with and without berm) at which more than 20 pressure sensors were installed. The results can be summarized as follows. The pressure measurements are reproduced well in the simulations. A grid with about 170 grid cells per wave length in the horizontal, and between 4 and 6 grid cells per wave height in the vertical, proves to be sufficiently fine. At such a grid resolution and with about 450 by 35 grid cells in the computational domain, a typical CPU time is 35 minutes for simulations with a model time of 10 wave periods. For the present application, it is preferable to use the one-phase flow model rather than the two-phase flow model, since the former gives better results in the lower located pressure sensors and consumes less CPU time.

Coupled solution of the Boltzmann and Navier–Stokes equations in gas–liquid two phase flow

2013 ◽  
Vol 71 ◽  
pp. 283-296 ◽  
Author(s):  
Sudarshan Tiwari ◽  
Axel Klar ◽  
Steffen Hardt ◽  
Alexander Donkov
Keyword(s):  
Two Phase Flow ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Phase Flow ◽  
Two Phase ◽  
Navier Stokes Equations ◽  
Coupled Solution

An Improved Volume of Fluid Method for Two-Phase Flow Computations on Collocated Grid System

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Dong-Liang Sun ◽  
Yong-Ping Yang ◽  
Jin-Liang Xu ◽  
Wen-Quan Tao
Keyword(s):  
Two Phase Flow ◽  
Stokes Equations ◽  
Volume Of Fluid ◽  
Vof Method ◽  
Navier Stokes ◽  
Phase Flow ◽  
Volume Of Fluid Method ◽  
Two Phase ◽  
Navier Stokes Equations ◽  
Collocated Grid

An improved volume of fluid method called the accurate density and viscosity volume of fluid (ADV-VOF) method is proposed to solve two-phase flow problems. The method has the following features: (1) All operations are performed on a collocated grid system. (2) The piecewise linear interface calculation is used to capture interfaces and perform accurate estimations of cell-edged density and viscosity. (3) The conservative Navier–Stokes equations are solved with the convective term discretized by a second and third order interpolation for convection scheme. (4) A fractional-step method is applied to solve the conservative Navier–Stokes equations, and the BiCGSTAB algorithm is used to solve the algebraic equations by discretizing the pressure-correction equation. The above features guarantee a simple, stable, efficient, and accurate simulation of two-phase flow problems. The effectiveness of the ADV-VOF method is verified by comparing it with the conventional volume of fluid method with rough treatment of cell-edged density and viscosity. It is found that the ADV-VOF method could successfully model the two-phase problems with large density ratio and viscosity ratio between two phases and is better than the conventional volume of fluid method in this respect.

On convergent schemes for two-phase flow of dilute polymeric solutions

2018 ◽  
Vol 52 (6) ◽  
pp. 2357-2408 ◽  
Author(s):  
Stefan Metzger
Keyword(s):  
Finite Element ◽  
Two Phase Flow ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Phase Flow ◽  
Two Phase ◽  
Extra Stress Tensor ◽  
Spring Force ◽  
Polymeric Solutions ◽  
Fokker Planck

We construct a Galerkin finite element method for the numerical approximation of weak solutions to a recent micro-macro bead-spring model for two-phase flow of dilute polymeric solutions derived by methods from nonequilibrium thermodynamics ([Grün, Metzger, M3AS 26 (2016) 823–866]). The model consists of Cahn-Hilliard type equations describing the evolution of the fluids and the unsteady incompressible Navier-Stokes equations in a bounded domain in two or three spatial dimensions for the velocity and the pressure of the fluids with an elastic extra-stress tensor on the right-hand side in the momentum equation which originates from the presence of dissolved polymer chains. The polymers are modeled by dumbbells subjected to a finitely extensible, nonlinear elastic (FENE) spring-force potential. Their density and orientation are described by a Fokker-Planck type parabolic equation with a center-of-mass diffusion term. We perform a rigorous passage to the limit as the spatial and temporal discretization parameters simultaneously tend to zero, and show that a subsequence of these finite element approximations converges towards a weak solution of the coupled Cahn-Hilliard-Navier-Stokes-Fokker-Planck system. To underline the practicality of the presented scheme, we provide simulations of oscillating dilute polymeric droplets and compare their oscillatory behaviour to the one of Newtonian droplets.

scholarly journals Slug Regime Transitions in a Two-Phase Flow in Horizontal Round Pipe. CFD Simulations

2020 ◽  
Vol 10 (23) ◽  
pp. 8739
Author(s):  
Vitaly Sergeev ◽  
Nikolai Vatin ◽  
Evgeny Kotov ◽  
Darya Nemova ◽  
Svyatoslav Khorobrov
Keyword(s):  
Pressure Drop ◽  
Flow Regime ◽  
Two Phase Flow ◽  
Stokes Equations ◽  
Bubbly Flow ◽  
Fluid Motion ◽  
Navier Stokes ◽  
Technical Solution ◽  
Phase Flow ◽  
Two Phase

The main objective of the study is to propose a technical solution integrated into the pipeline for the transition of the flow regime from slug to bubbly two-phase flow. The object of research is isothermal two-phase gas–Newtonian-liquid flow in a horizontal circular pipeline. There is local resistance in the pipe in the form of a streamlined transverse mesh partition. The mesh partition ensures the transition of the flow from the slug regime to the bubbly regime. The purpose of the study is to propose a technical solution integrated into the pipeline for changing the flow regime of a two-phase flow from slug to bubbly flow. The method of research is a simulation using computational fluid dynamics (CFD) numerical simulation. The Navier–Stokes equations averaged by Reynolds describes the fluid motion. The k-ε models were used to close the Reynolds-averaged Navier–Stokes (RANS) equations. The computing cluster «Polytechnic—RSK Tornado» was used to solve the tasks. The results of simulation show that pressure drop on the grid did not exceed 10% of the pressure drop along the length of the pipeline. The mesh partition transits the flow regime from slug to layered one, which will help to increase the service life and operational safety of a real pipeline at insignificant energy costs to overcome the additional resistance integrated into the pipeline.

Simulating working bodies in the mixer of a low-thrust liquid propellant rocket engine with a thrust of 10 to 15 N: comparing three models of flow and mixing based on solving Reynolds-averaged Navier — Stokes equations

2021 ◽  
Author(s):  
E.V. Semkin
Keyword(s):  
Flow Model ◽  
Stokes Equations ◽  
Rocket Engine ◽  
Navier Stokes ◽  
Low Thrust ◽  
Two Phase ◽  
Navier Stokes Equations ◽  
Velocity Flow ◽  
Liquid Propellant Rocket Engine ◽  
Working Bodies

The paper analyses the possibilities of using the ANSYS CFX hydrocode to simulate the flow and mixing of working bodies in the mixer and combustion chamber of a low-thrust liquid propellant rocket engine in the thrust range of 10 to 15 N. We built our models around solving Reynolds-averaged Navier — Stokes equations stated for three types of multiphase multicomponent incompressible fluid flow: a two-phase two-component two-velocity flow model; a two-phase two-component single-velocity flow model; a three-phase three-velocity flow model. We consider the advantages and disadvantages of each model. We compare our simulation results to the results of measurements conducted during hydraulic testing of mixers.

Numerical Study of Liquid Slug Stability During Adiabatic Two Phase Flow Inside a Minichannel

2007 ◽  
Author(s):  
A. Mukherjee ◽  
J. S. Allen
Keyword(s):  
Contact Angle ◽  
Continuity Equation ◽  
Stokes Equations ◽  
Numerical Study ◽  
Navier Stokes ◽  
Phase Flow ◽  
Liquid Slug ◽  
Two Phase ◽  
Navier Stokes Equations ◽  
Liquid Plug

The present study is performed to analyze stability of a liquid meniscus inside a microchannel. A liquid plug is placed inside a microchannel and the shape and stability of upstream and downstream interfaces have been studied for different airflow rates. The thickness of the liquid plug and the contact angle has been varied systematically. In the numerical model the complete Navier-Stokes equations along with continuity equation are solved using the SIMPLER method. The liquid vapor interface is captured using the level set technique. The liquid plug is seen to move downstream along with the air and surface instabilities are noted at the upstream and downstream interfaces. At low contact angle, water is found to accumulate at the channel corners due to capillary forces causing the slug to disintegrate. The numerical results are found to be qualitatively similar to experimental data.

A fast massively parallel two-phase flow solver for microfluidic chip simulation

2016 ◽  
Vol 32 (2) ◽  
pp. 266-287 ◽  
Author(s):  
Martin Kronbichler ◽  
Ababacar Diagne ◽  
Hanna Holmgren
Keyword(s):  
Adaptive Mesh Refinement ◽  
Degrees Of Freedom ◽  
Large Scale ◽  
Two Phase Flow ◽  
Stokes Equations ◽  
Adaptive Mesh ◽  
Navier Stokes ◽  
Implicit Time ◽  
Phase Flow ◽  
Two Phase

This work presents a parallel finite element solver of incompressible two-phase flow targeting large-scale simulations of three-dimensional dynamics in high-throughput microfluidic separation devices. The method relies on a conservative level set formulation for representing the fluid-fluid interface and uses adaptive mesh refinement on forests of octrees. An implicit time stepping with efficient block solvers for the incompressible Navier–Stokes equations discretized with Taylor–Hood and augmented Taylor–Hood finite elements is presented. A matrix-free implementation is used that reduces the solution time for the Navier–Stokes system by a factor of approximately three compared to the best matrix-based algorithms. Scalability of the chosen algorithms up to 32,768 cores and a billion degrees of freedom is shown.

Simulation of the Dynamic Response of a Sloshing Liquid to Horizontal Movements of the Tank

2014 ◽  
Author(s):  
Anaïs Brandely ◽  
Jean-Sébastien Schotté ◽  
Emmanuel Lefrançois ◽  
Benjamin Hagege ◽  
Roger Ohayon
Keyword(s):  
Free Surface ◽  
Dynamic Response ◽  
Stokes Equations ◽  
Numerical Approach ◽  
Navier Stokes ◽  
Phase Flow ◽  
Viscous Effects ◽  
Two Phase ◽  
Navier Stokes Equations ◽  
Sst Turbulence Model

The dynamic response of a sloshing liquid to horizontal movements of a rectangular tank with a small amplitude is studied here by a numerical approach issued from a commercial CFD code. This numerical model solves Navier-Stokes equations considering a two-phase flow. In order to check the localized turbulence effects on the global fluid behavior, the averaged Navier-Stokes equations are solved with laminar option and with a k–ω SST turbulence model. The Volume Of Fluid (VOF) method is adopted to track the distorted free surface. The previous CFD solution is compared with a linearized approach based on the potential flow theory taking into account viscous effects. This model considers a single phase flow and is much less expensive in CPU time, especially thanks to the use of modal projection techniques. Both models are validated and applied on several cases. Free surface sloshing elevation and global forces, obtained for various excitation amplitudes and frequencies, are compared. Perfect and viscous liquids are considered.

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