On a Numerical Model for Free Surface Flows of a Conductive Liquid Under an Electrostatic Field

2012 ◽  
Vol 134 (9) ◽  
Author(s):  
Sajad Pooyan ◽  
Mohammad Passandideh-Fard
Keyword(s):  
Free Surface ◽  
Numerical Model ◽  
Electric Field ◽  
Electrostatic Field ◽  
Stokes Equations ◽  
Free Surface Flows ◽  
Computational Method ◽  
Perfect Conductor ◽  
Computational Domain ◽  
Conductive Liquid

In this paper, a numerical model is developed that can simulate the unsteady axisymmetric free-surface flow of a perfectly conductive liquid under an electrostatic field. The effect of the electrostatic field is modeled by a force distributed on the liquid free surface. Assuming the liquid as a perfect conductor makes it possible to reduce the general electromagnetic equations to electrostatic equations. The Navier–Stokes equations are solved to find the velocity and pressure fields. The free surface advection and reconstruction are performed based on the volume-of-fluid method using Youngs’ algorithm. To evaluate the effect of the electric field on the free surface, the electrostatic potential is first solved for the entire computational domain. Next, the electric field intensity and the surface density of the electric charge are calculated on the free surface after which the electric force can be determined. The computational method for treating this force is similar to that of the surface tension using the continuum surface force method. The developed model is validated by a comparison between the calculated results with those of the analytics as well as experiments for an electrowetting scenario.

Simulation of free surface flows using volume of fluid method and genetic algorithm

2014 ◽  
Vol 16 (5) ◽  
pp. 1110-1124 ◽  
Author(s):  
N. Soleiman Beygi ◽  
H. Hakimzadeh ◽  
M. R. Chenaglou
Keyword(s):  
Genetic Algorithm ◽  
Fluid Flow ◽  
Free Surface ◽  
Stokes Equations ◽  
Volume Of Fluid ◽  
Free Surface Flows ◽  
Computational Domain ◽  
Tracking Method ◽  
Surface Tracking ◽  
Donor And Acceptor

In this paper, details of a numerical model development for simulation of fluid flows with moving free surface are presented. The unsteady incompressible Navier–Stokes equations on a fixed grid system are used to obtain velocity and pressure values in the computational domain and volume of fluid (VOF) method is used to determine free surface location. In order to reduce numerical smearing and increase accuracy of numerical modeling of fluid flow with moving free surface, a new free surface-tracking method is proposed. The proposed method is a combination of genetic algorithm and free surface tracking method based on donor and acceptor scheme. The specification of the new combinational method can be summarized in determining orientation vector and plane constant to represent the free surface orientation in each cell. The proposed algorithm can be easily used in any unstructured grids. In this method, the fluid flow equations are explicitly discretized with the finite volume method and the projection method is used to determine the velocity and pressure magnitude in computational domain. Validity of the new solution algorithm is demonstrated through its application to the dam break and the bore motion examples.

scholarly journals A Hybrid Parallel Numerical Model for Wave-Induced Free-Surface Flow

Fluids ◽  
2021 ◽  
Vol 6 (10) ◽  
pp. 350
Author(s):  
Georgios A. Leftheriotis ◽  
Iason A. Chalmoukis ◽  
Guillermo Oyarzun ◽  
Athanassios A. Dimas
Keyword(s):  
Free Surface ◽  
Numerical Model ◽  
Large Scale ◽  
Stokes Equations ◽  
Parallel Implementation ◽  
Three Dimensional ◽  
Free Surface Flow ◽  
Free Surface Flows ◽  
Surface Flow ◽  
Wave Induced

An advanced numerical model is presented for the simulation of wave-induced free-surface flow, utilizing an efficient hybrid parallel implementation. The model is based on the solution of the Navier–Stokes equations using large-eddy simulation of large-scale coastal free-surface flows. The three-dimensional immersed boundary method was used for the enforcement of the no-slip boundary condition on the bed surface. The water-air interface was tracked using the level-set method. The numerical model was effectively validated against laboratory measurements involving wave propagation over a flatbed with an elliptical shoal, whose presence induces combined wave refraction and diffraction phenomena. The parallel implementation of the model enabled the efficient simulation of depth-resolved, wave-induced, three-dimensional, free-surface flow; the model parallel efficiency and strong scaling are quantitatively demonstrated.

Numerical Investigation of Focused Waves and Their Interaction With a Vertical Cylinder Using REEF3D

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Hans Bihs ◽  
Mayilvahanan Alagan Chella ◽  
Arun Kamath ◽  
Øivind Asgeir Arntsen
Keyword(s):  
Free Surface ◽  
Stokes Equations ◽  
Free Surface Flows ◽  
Surface Elevation ◽  
Numerical Wave Tank ◽  
Free Surface Elevation ◽  
Wave Tank ◽  
Numerical Wave ◽  
Focused Wave ◽  
The Impact

For the stability of offshore structures, such as offshore wind foundations, extreme wave conditions need to be taken into account. Waves from extreme events are critical from the design perspective. In a numerical wave tank, extreme waves can be modeled using focused waves. Here, linear waves are generated from a wave spectrum. The wave crests of the generated waves coincide at a preselected location and time. Focused wave generation is implemented in the numerical wave tank module of REEF3D, which has been extensively and successfully tested for various wave hydrodynamics and wave–structure interaction problems in particular and for free surface flows in general. The open-source computational fluid dynamics (CFD) code REEF3D solves the three-dimensional Navier–Stokes equations on a staggered Cartesian grid. Higher order numerical schemes are used for time and spatial discretization. For the interface capturing, the level set method is selected. In order to test the generated waves, the time series of the free surface elevation are compared with experimental benchmark cases. The numerically simulated free surface elevation shows good agreement with experimental data. In further computations, the impact of the focused waves on a vertical circular cylinder is investigated. A breaking focused wave is simulated and the associated kinematics is investigated. Free surface flow features during the interaction of nonbreaking focused waves with a cylinder and during the breaking process of a focused wave are also investigated along with the numerically captured free surface.

scholarly journals Modeling Free Surface Flows Using Stabilized Finite Element Method

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Deepak Garg ◽  
Antonella Longo ◽  
Paolo Papale
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Free Surface ◽  
Numerical Scheme ◽  
Stokes Equations ◽  
Fluid Velocity ◽  
Computer Code ◽  
Free Surface Flows ◽  
Surface Flows ◽  
Element Method

This work aims to develop a numerical wave tank for viscous and inviscid flows. The Navier-Stokes equations are solved by time-discontinuous stabilized space-time finite element method. The numerical scheme tracks the free surface location using fluid velocity. A segregated algorithm is proposed to iteratively couple the fluid flow and mesh deformation problems. The numerical scheme and the developed computer code are validated over three free surface problems: solitary wave propagation, the collision between two counter moving waves, and wave damping in a viscous fluid. The benchmark tests demonstrate that the numerical approach is effective and an attractive tool for simulating viscous and inviscid free surface flows.

Numerical Modeling of Flow Over a Dam Spillway

2006 ◽  
Author(s):  
Iraj Saeedpanah ◽  
M. Shayanfar ◽  
E. Jabbari ◽  
Mohammad Haji Mohammadi
Keyword(s):  
Free Surface ◽  
Stokes Equations ◽  
Iterative Solution ◽  
Free Surface Flows ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Continuity Equations ◽  
Water Jets ◽  
Pressure Fields ◽  
Good Agreement

Free surface flows are frequently encountered in hydraulic engineering problems including water jets, weirs and around gates. An iterative solution to the incompressible two-dimensional vertical steady Navier-Stokes equations, comprising momentum and continuity equations, is used to solve for the priori unknown free surface, the velocity and the pressure fields. The entire water body is covered by a unstructured finite element grid which is locally refined. The dynamic boundary condition is imposed for the free surface where the pressure vanishes. This procedure is done continuously until the normal velocities components vanish. To overcome numerical errors and oscillations encountering in convection terms, the SUPG (streamline upwinding Petrov-Galerkin) method is applied. The solution method is tested for different discharges onto a standard spillway geometries. The results shows good agreement with available experimental data.

Numerical Simulation of Nonlinear Water Wave Propagation Over Rippled Bed

2007 ◽  
Author(s):  
Gerasimos A. Kolokythas ◽  
Athanassios A. Dimas
Keyword(s):  
Free Surface ◽  
Boundary Conditions ◽  
Water Waves ◽  
Stokes Equations ◽  
Surface Flow ◽  
Surface Boundary ◽  
Computational Domain ◽  
Time Step ◽  
Outflow Boundary ◽  
Rippled Bed

In the present study, numerical simulations of the free-surface flow, developing by the propagation of nonlinear water waves over a rippled bottom, are performed assuming that the corresponding flow is two-dimensional, incompressible and viscous. The simulations are based on the numerical solution of the Navier-Stokes equations subject to the fully-nonlinear free-surface boundary conditions and the suitable bottom, inflow and outflow boundary conditions. The equations are properly transformed so that the computational domain becomes time-independent. For the spatial discretization, a hybrid scheme with finite-differences and Chebyshev polynomials is applied, while a fractional time-step scheme is used for the temporal discretization. A wave absorption zone is placed at the outflow region in order to efficiently minimize reflection of waves by the outflow boundary. The numerical model is validated by comparison to the analytical solution for the laminar, oscillatory, current flow which develops a uniform boundary layer over a horizontal bottom. For the propagation of finite-amplitude waves over a rigid rippled bed, the case with wavelength to water depth ratio λ/d0 = 6 and wave height to wavelength ratio H0/λ = 0.05 is considered. The ripples have parabolic shape, while their dimensions — length and height — are chosen accordingly to fit laboratory and field data. Results indicate that the wall shear stress over the ripples and the form drag forces on the ripples increase with increasing ripple height, while the corresponding friction force is insensitive to this increase. Therefore, the percentage of friction in the total drag force decreases with increasing ripple height.

scholarly journals Numerical modeling of fluid resonance in narrow gaps of fixed rectangular structures

2019 ◽  
Vol 11 (8) ◽  
pp. 168781401987230
Author(s):  
Ming-ming Liu ◽  
Rui-jia Jin ◽  
Zhen-dong Cui
Keyword(s):  
Free Surface ◽  
Numerical Model ◽  
Stokes Equations ◽  
Theoretical Data ◽  
Numerical Results ◽  
Two Dimensional ◽  
Arbitrary Lagrangian Eulerian ◽  
Fluid Resonance ◽  
Resonance Wave ◽  
Narrow Gaps

A two-dimensional numerical model is developed to investigate the phenomenon of resonance in narrow gaps. Instead of using commonly used Volume of Fluid method to capture the free surface which is sometimes difficult to capture the geometric properties of the geometrically complicated interface, the free surface is traced by using Arbitrary Lagrangian–Eulerian method. The numerical model is based on the two-dimensional Reynolds-Averaged Navier–Stokes equations. The numerical model is validated against wave propagation in wave flume. Comparisons between the numerical results and available theoretical data show satisfactory agreements. Fluid resonance in narrow gaps of fixed rectangular structures are simulated. Numerical results show that resonance wave height and wave frequency for rectangle boxes with sphenoid corners is larger than for rectangle boxes.

Design of Coaxial Needleless Electrospinning Electrode with Respect to the Distribution of Electric Field

2014 ◽  
Vol 693 ◽  
pp. 394-399 ◽  
Author(s):  
Lucie Vysloužilová ◽  
Jan Valtera ◽  
Karel Pejchar ◽  
Jaroslav Beran ◽  
David Lukáš
Keyword(s):  
Free Surface ◽  
Electric Field ◽  
Electrostatic Field ◽  
Electric Energy ◽  
Electrospinning Process ◽  
Coaxial Electrospinning ◽  
Core Shell ◽  
Process Stability ◽  
Field Simulation ◽  
Sharp Edges

The paper is focused on the design of the electrode for needleless coaxial electrospinning. This method allows to produce core/shell nanofibers from the free surface of a polymeric two-layer. The geometry of the designed model of electrode was analyzed using the software Autodesk Simulation Multiphysics. The results of electrostatic field simulation indicate the sharp edges of the electrode as the source of high electric intensity. These sharp edges lead to the loss of the electric energy during the electrospinning process. Based on that, the new cylindrical geometry of the electrode was developed. The results of carried out experiments clearly demonstrate the enhancement of the electrospinning process stability.

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