scholarly journals Modelling and assessment of 137-Cs and of heavy metals impact on marine ecosystems

2020 ◽  
Vol 19 ◽  
pp. 119
Author(s):  
M. Psaltaki ◽  
N. C. Markatos
Keyword(s):  
Stokes Equations ◽  
Deterministic Model ◽  
Three Dimensional ◽  
Aegean Sea ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Flow Heat ◽  
Local Ecosystem ◽  
Volume Method ◽  
The Impact

Modelling is an important and useful tool for predicting the behaviour and the impact of pollutants on the local ecosystem parameters. More specifically, simulation and computational methods can be used for estimating the environmental impact on marine ecosystems.The paper presents a three-dimensional general deterministic model, developed to simulate and study the time-dependent behaviour of 137Cs in marine environments. The model capabilities are demonstrated by applying it at the northeast region of the island of Lemnos, in the NE Aegean Sea, Greece. Full Navier-Stokes equations for transient, three-dimensional turbulent flow, heat and mass transfer are solved numerically. The solution method is the finite-volume method and the general CFD code in which the present model is implemented is Phoenics.

scholarly journals Three-Dimensional Numerical Study of the Effect of Protective Barrier on the Dispersion of the Contaminant in a Building

Mathematics ◽  
2021 ◽  
Vol 9 (10) ◽  
pp. 1125
Author(s):  
Chemseddine Maatki
Keyword(s):  
Rayleigh Number ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Vorticity Vector ◽  
Volume Method ◽  
The Impact ◽  
Buoyancy Ratio

The finite volume method and potential-vorticity vector formalism in their three-dimensional form were used to numerically study the impact of an adiabatic and impermeable vertical barrier on the dispersion of a local aero-contaminant due to the double-diffusive Rayleigh–Benard convection inside a cubic container. Different governing parameters such as the Rayleigh number, buoyancy ratio and barrier height were analyzed for Le = 1.2 and Pr = 0.7, representing an air-contaminant mixture. The potential-vector-vorticity formalism in the three-dimensional form allowed the elimination of the pressure terms appearing in the Navier–Stokes equations. It was found that the heat and mass transfer as well as the effectiveness of the barrier in reducing contaminant dispersion are strongly influenced by the buoyancy ratio, the barrier size and the Rayleigh number. In addition, the barrier effectiveness is more than 70% for a height of half the building height.

scholarly journals Dynamics of Single Droplet Splashing on Liquid Film by Coupling FVM with VOF

Processes ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 841
Author(s):  
Yuzhen Jin ◽  
Huang Zhou ◽  
Linhang Zhu ◽  
Zeqing Li
Keyword(s):  
Liquid Film ◽  
Weber Number ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Single Droplet ◽  
Navier Stokes Equations ◽  
Volume Method ◽  
The Relationship

A three-dimensional numerical study of a single droplet splashing vertically on a liquid film is presented. The numerical method is based on the finite volume method (FVM) of Navier–Stokes equations coupled with the volume of fluid (VOF) method, and the adaptive local mesh refinement technology is adopted. It enables the liquid–gas interface to be tracked more accurately, and to be less computationally expensive. The relationship between the diameter of the free rim, the height of the crown with different numbers of collision Weber, and the thickness of the liquid film is explored. The results indicate that the crown height increases as the Weber number increases, and the diameter of the crown rim is inversely proportional to the collision Weber number. It can also be concluded that the dimensionless height of the crown decreases with the increase in the thickness of the dimensionless liquid film, which has little effect on the diameter of the crown rim during its growth.

Effect of the Separating Distance of Twin Buildings on the Generated Flow Structure

2010 ◽  
Vol 297-301 ◽  
pp. 924-929
Author(s):  
Inès Bhouri Baouab ◽  
Nejla Mahjoub Said ◽  
Hatem Mhiri ◽  
Georges Le Palec ◽  
Philippe Bournot
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Reynolds Stress Model ◽  
Navier Stokes ◽  
Wind Flow ◽  
Turbulent Model ◽  
Navier Stokes Equations ◽  
Twin Buildings ◽  
Volume Method ◽  
Numerical Examination

The present work consists in a numerical examination of the dispersion of pollutants discharged from a bent chimney and crossing twin similar cubic obstacles placed in the lee side of the source. The resulting flow is assumed to be steady, three-dimensional and turbulent. Its modelling is based upon the resolution of the Navier Stokes equations by means of the finite volume method together with the RSM (Reynolds Stress Model) turbulent model. This examination aims essentially at detailing the wind flow perturbations, the recirculation and turbulence generated by the presence of the twin cubic obstacles placed tandem at different spacing distances (gaps): W = 4 h, W = 2 h and W = 1 h where W is the distance separating both buildings.

Numerical Simulation on Undulatory Flow of Swimming Fish

2013 ◽  
Vol 353-356 ◽  
pp. 2545-2549
Author(s):  
Xu Zhang ◽  
Xiu Bin He
Keyword(s):  
Numerical Simulation ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Time Stepping ◽  
Dual Time Stepping ◽  
Straight Line ◽  
Volume Method ◽  
Undulatory Swimming

A numerical simulation is carried out to investigate the unsteady flows over a swimming fish. The three-dimensional incompressible Navier-Stokes equations are solved using the finite volume method with artificial compressibility and dual time stepping approaches on unstructured moving grid. A realistic fish-like body is modeled, which undergoes undulatory swimming in a straight line. Both inviscid and viscous flows have been simulated to study the flow structures.

Influence of Rotor-Stator Interaction on Flow Stability in Centrifugal Pump Based on Energy Gradient Method

2016 ◽  
Vol 33 (4) ◽  
Author(s):  
Lu-Lu Zheng ◽  
Hua-Shu Dou ◽  
Wei Jiang ◽  
Xiaoping Chen ◽  
Zuchao Zhu ◽  
...  
Keyword(s):  
Centrifugal Pump ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Simple Algorithm ◽  
Navier Stokes ◽  
Turbulent Model ◽  
Navier Stokes Equations ◽  
Energy Gradient ◽  
Rotor Stator Interaction ◽  
Volume Method

AbstractNumerical simulation is performed for the three-dimensional turbulent flow field in a centrifugal pump by solving the Reynolds-averaged Navier-Stokes equations and the RNG k-epsilon turbulent model. The finite volume method and the SIMPLE algorithm are employed for the solution of the system. All the parameters in the centrifugal pump at different blade angular positions are obtained by simulation. The flow structure is analyzed and the distributions of the energy gradient function

Evaluation of numerical diffusion of the finite volume method when modelling surface waves

2019 ◽  
pp. 106-119
Author(s):  
Елена Сергеевна Тятюшкина ◽  
Андрей Сергеевич Козелков ◽  
Андрей Александрович Куркин ◽  
Вадим Викторович Курулин ◽  
Валентин Робертович Ефремов ◽  
...  
Keyword(s):  
Finite Volume Method ◽  
Finite Volume ◽  
Calculation Method ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Time Step ◽  
Navier Stokes Equations ◽  
Numerical Diffusion ◽  
Volume Method

Обсуждается применение метода конечных объемов при решении уравнений Навье-Стокса для моделирования поверхностных волн. Сформулирована задача о распространении поверхностных волн, которая используется для оценки численной диффузии в решении уравнений Навье-Стокса. Предлагается методика оценки численной диффузии, выражаемой коэффициентом уменьшения амплитуды волны при прохождении ею одной своей длины (коэффициентом затухания). Дана оценка размеров сетки и шага по времени, выраженных в безразмерных величинах относительно параметров волны, необходимых для обеспечения приемлемого значения коэффициента затухания. Показана степень влияния каждого из сеточных параметров на увеличение коэффициента затухания. The application of numerical simulation methods based on the solution of the full three-dimensional Navier-Stokes equations for modelling of wave propagation on the water surface requires the construction of a grid model containing countable nodes throughout the entire volume of water medium. Insufficient grid resolution leads to insufficient detailing of the fields of velocity and pressure, as well as volume fraction of the liquid, which increases the numerical diffusion of the method and, ultimately, leads to an underestimation of oscillation amplitudes of the medium. A large time step also results in a “blurring” of the solution and significantly reduces its stability, especially when using the schemes which compress the front of the media interface. This paper presents the results of an assessment of acceptable grid sizes and time steps expressed in dimensionless parameters with respect to the wave parameters necessary to ensure accuracy of the solution sufficient for geophysical applications. The estimate is given for the method of calculating three-dimensional multiphase flows with a free surface based on solving the Navier-Stokes equations in a one-velocity approximation based on a completely implicit connection between velocity and pressure using the finite volume method. The finite volume method for the numerical solution of the Navier-Stokes equations is implemented for use on arbitrary unstructured grids. The methodology for estimation of numerical diffusion of the calculation method is proposed. This estimation is expressed as a percentage of the wave amplitude decrease at the distance equal to the one wavelength. In turn the methodology is based on the parameters entered to estimate the acceptable grid sizes and time step for the calculation method. Based on the described methodology, the results of the estimation of the grid resolution in the horizontal and vertical directions, the estimation of the time step, and the evaluation of the influence of the discretization scheme of the convective term are presented.

Single-Wave Peristalsis

2000 ◽  
Author(s):  
M. Tadjfar ◽  
T. Yamaguchi ◽  
R. Himeno
Keyword(s):  
Incompressible Flows ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Cylindrical Tube ◽  
Transient State ◽  
Navier Stokes ◽  
Wave Flow ◽  
Navier Stokes Equations ◽  
Single Wave ◽  
Volume Method

Abstract Single-wave peristalsis propagating on the wall of a cylindrical tube is simulated. The unsteady, three-dimensional, incompressible Navier-Stokes equations are solved numerically. The flow is computed with moving boundaries and moving grid. A second-order in time and third-order upwind finite volume method for solving time-accurate incompressible flows utilizing pseudo-compressibility technique is used. In this study, the flow of an axisymmetric “tear-drop” shaped, single, peristaltic wave is analyzed. The effect of transient state on the flow is limited. The three-dimensional effects are also limited to the transient state. The lubrication theory application to the single wave flow may not be appropriate due to its inability to adjust the pressure nonlinearly.

scholarly journals A Stabilized Low Order Finite-Volume Method for the Three-Dimensional Stationary Navier-Stokes Equations

2012 ◽  
Vol 2012 ◽  
pp. 1-14
Author(s):  
Jian Li ◽  
Xin Zhao ◽  
Jianhua Wu ◽  
Jianhong Yang
Keyword(s):  
Finite Volume Method ◽  
Finite Volume ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Uniqueness Condition ◽  
Navier Stokes Equations ◽  
Volume Method ◽  
Stationary Navier Stokes Equations ◽  
Superconvergence Results

This paper proposes and analyzes a stabilized finite-volume method (FVM) for the three-dimensional stationary Navier-Stokes equations approximated by the lowest order finite element pairs. The method studies the new stabilized FVM with the relationship between the stabilized FEM (FEM) and the stabilized FVM under the assumption of the uniqueness condition. The results have three prominent features in this paper. Firstly, the error analysis shows that the stabilized FVM provides an approximate solution with the optimal convergence rate of the same order as the usual stabilized FEM solution solving the stationary Navier-Stokes equations. Secondly, superconvergence results on the solutions of the stabilized FEM and stabilized FVM are derived on theH1-norm and theL2-norm for the velocity and pressure. Thirdly, residual technique is applied to obtain theL2-norm error for the velocity without additional regular assumption on the exact solution.

Analysis of Loads and Response on Flexible Riser under the Combined Effects of Wave and Current

2015 ◽  
Vol 723 ◽  
pp. 120-124 ◽  
Author(s):  
Zi Xin Wu ◽  
Ren Qing Zhu ◽  
Si Qi Gu ◽  
Zhi Ping Xia ◽  
Yang Luo ◽  
...  
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Flexible Riser ◽  
Navier Stokes Equations ◽  
Volume Method ◽  
System Coupling ◽  
Reynolds Average ◽  
Viscid Fluid ◽  
Module System

A three dimensional computational model is established for the analysis of loads and response of flexible riser in a wave-current coexisting environment. The viscid fluid is assumed incompressible. The flow field is described by continuity equation and Reynolds Average Navier-Stokes equations and solved with the discretization of Finite-Volume Method. The structure responses are analyzed employing finite element method based on three dimensional solid element. The loads and response are calculated through the CFD module System Coupling in software package ANSYS14.5. The results show that the vibration equilibrium position of riser offsets along with the direction of current when wave and current are in the same direction, the response of the riser is larger than that only in wave, the vibration amplitude increases with the current and the results are opposite to the above when wave and current has the opposite direction.

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