scholarly journals A Simultaneous Model for Simulating the Propagation of Hydraulic Head in Aquifers with Leakage Pathways

2016 ◽  
Vol 6 (2) ◽  
pp. 65
Author(s):  
Seong Jun Lee
Keyword(s):  
Three Dimensional ◽  
Numerical Code ◽  
Leakage Term ◽  
Transient Flows ◽  
Starting Time ◽  
Groundwater Aquifers ◽  
Finite Difference Equations ◽  
Hydraulic Gradients ◽  
Simultaneous Model ◽  
Multiple Aquifers

A three-dimensional simultaneous solution model was developed for analysis of variable transient flows, specifically leakage associated with arbitrary groundwater aquifers. The model simultaneously calculates leakage rates using the hydraulic gradients between coupled leakage points at two leaky aquifers and evaluates the propagation of hydraulic heads in multiple aquifers resulting from that leakage. Important considerations for leakage simulation are variant leakage rates with time and leakage starting time. Two types of leakage pathways are specified in terms of the generated time, including (1) pre-existing leakage pathways and (2) abruptly-induced leakage pathways at specific times. The governing equation with a leakage term is composed of three finite difference equations, and its form depends on whether leakage pathways pre-exist or are induced at specified times according to known or assumed aquifer histories. The developed numerical code was validated by comparison with the results of the TOUGH2/EOS1 program for a three-dimensional conceptual domain.

scholarly journals Numerical Simulation of the Coagulation Dynamics of Blood

2008 ◽  
Vol 9 (2) ◽  
pp. 83-104 ◽  
Author(s):  
T. Bodnár ◽  
A. Sequeira
Keyword(s):  
Blood Coagulation ◽  
Computational Study ◽  
Time Integration ◽  
Three Dimensional ◽  
Circular Cross Section ◽  
Clot Formation ◽  
Diffusion Reaction ◽  
Numerical Code ◽  
Injured Region ◽  
Reaction Equations

The process of platelet activation and blood coagulation is quite complex and not yet completely understood. Recently, a phenomenological meaningful model of blood coagulation and clot formation in flowing blood that extends existing models to integrate biochemical, physiological and rheological factors, has been developed. The aim of this paper is to present results from a computational study of a simplified version of this coupled fluid-biochemistry model. A generalized Newtonian model with shear-thinning viscosity has been adopted to describe the flow of blood. To simulate the biochemical changes and transport of various enzymes, proteins and platelets involved in the coagulation process, a set of coupled advection–diffusion–reaction equations is used. Three-dimensional numerical simulations are carried out for the whole model in a straight vessel with circular cross-section, using a finite volume semi-discretization in space, on structured grids, and a multistage scheme for time integration. Clot formation and growth are investigated in the vicinity of an injured region of the vessel wall. These are preliminary results aimed at showing the validation of the model and of the numerical code.

scholarly journals Modeling the 3-d flow around a cylinder using the SAS hybrid model

2014 ◽  
Vol 16 (5) ◽  
pp. 901-918 ◽  
Keyword(s):  
Turbulence Modeling ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Cross Flow ◽  
Numerical Code ◽  
Navier Stokes ◽  
Computational Domain ◽  
Mean Flow ◽  
Unstable Flow ◽  
Vortex Size

<div> <p>Three-dimensional calculations were performed to simulate the flow around a cylindrical vegetation element using the Scale Adaptive Simulation (SAS) model; commonly, this is the first step of the modeling of the flow through multiple vegetation elements. SAS solves the Reynolds Averaged Navier-Stokes equations in stable flow regions, while in regions with unstable flow it goes unsteady producing a resolved turbulent spectrum after reducing eddy viscosity according to the locally resolved vortex size represented by the von Karman length scale. A finite volume numerical code was used for the spatial discretisation of the rectangular computational domain with stream-wise, cross-flow and vertical dimensions equal to 30D, 11D and 1D, respectively, which was resolved with unstructured grids. Calculations were compared with experiments and Large Eddy Simulations (LES). Predicted overall flow parameters and mean flow velocities exhibited a very satisfactory agreement with experiments and LES, while the agreement of predicted turbulent stresses was satisfactory. Calculations showed that SAS is an efficient and relatively fast turbulence modeling approach, especially in relevant practical problems, in which the very high accuracy that can be achieved by LES at the expense of large computational times is not required.</p> </div> <p>&nbsp;</p>

scholarly journals Spectral properties of magnetohydrodynamic convection with mean horizontal temperature gradient

2006 ◽  
Vol 2 (S239) ◽  
pp. 513-513
Author(s):  
D. Skandera ◽  
W.-Ch. Müller
Keyword(s):  
Temperature Field ◽  
Rayleigh Number ◽  
Temperature Gradient ◽  
Numerical Simulations ◽  
Spectral Properties ◽  
Three Dimensional ◽  
Numerical Code ◽  
Dimensional System ◽  
Horizontal Temperature Gradient ◽  
Mhd Turbulence

AbstractSpectral properties of convective magnetohydrodynamic (MHD) turbulence in two and three dimensions are studied by means of direct numerical simulations (Skandera D. & Müller W.-C. 2006). The investigated system is set up with a mean horizontal temperature gradient in order to avoid a development of elevator instabilities in a fully periodic box. All simulations are performed without mean magnetic field. The applied resolution is 5123 and 20482. The MHD equation are solved by a numerical code (Müller & Biskamp 2000) that uses a standard pseudospectral scheme. For removing of aliasing errors a spherical truncation method is employed. Obtained results are compared with predictions of various existing phenomenological theories for magnetohydrodynamic and convective turbulence (Müller & Biskamp 2000). While the three-dimensional system is found to operate in a Kolmogorov-like regime where buoyant forces have a negligible impact on the turbulence dynamics (relatively low Rayleigh number achieved in the simulation; Ra ∼106), the two-dimensional system exhibits interesting irregular quasi-oscillations between a buoyancy dominated Bolgiano-Obukhov-like regime of turbulence and a standard Iroshnikov-Kraichnan-like regime of turbulence (Müller & Biskamp 2000). The most important parameter determining the turbulent regime of 2D magnetoconvection, apart from a high Rayleigh number, seems to be the mutual alignment of velocity and magnetic fields. The non-linear dynamics and the interplay between individual fields are examined with different transfer functions that confirm basic assumptions about directions of energy transfer in spectral space. Kinetic, magnetic and temperature energy are transported by a turbulent cascade from large to smaller scales. The local/nonlocal character of the transport is tested for several individual terms in the governing equations. Moreover, other statistical quantities, e.g. probability density functions, are computed as well. A passive character of the temperature field in the investigated three-dimensional magnetoconvection is supported by computations of intermittency using extended self-similarity. The intermittency of the Elsasser field z+ is in agreement with results from numerical simulations of isotropic MHD turbulence (Müller & Biskamp 2000). The intermittency of the temperature field is found to approximately agree with results of passive scalar measurements in hydrodynamic turbulence (Ruiz-Chavarria, Baudet & Ciliberto 1996).

Numerical simulation of airflow characteristics in the spinning zone at starting time of air-jet spinning machine

2018 ◽  
Vol 89 (12) ◽  
pp. 2342-2352
Author(s):  
Thi Viet Bac Phung ◽  
Akihiro Yoshida ◽  
Yoshiyuki Iemoto ◽  
Hideyuki Uematsu ◽  
Shuichi Tanoue
Keyword(s):  
Fiber Bundle ◽  
High Speed ◽  
Three Dimensional ◽  
Swirl Flow ◽  
Air Pressure ◽  
Suction Force ◽  
Starting Time ◽  
Air Jet ◽  
Spinning Process ◽  
Center Axis

To clarify the formation mechanism of a source of yarn and to discuss the effects of supplied air pressure and exhaust air pressure on the fiber suction force and twist torque at the starting time of the spinning process in an air-jet spinning machine, we simulated, numerically, the three-dimensional airflow pattern without fibers in the spinning zone. Results obtained are as follows: High-speed air jetted through the starting nozzles into the yarn duct in the circumferential direction causes a swirl flow in the yarn duct and a negative pressure region near the center axis of the yarn duct. Hence, air and fibers at the fiber inlet are sucked through the processing duct into the yarn duct. A fiber bundle sucked into the yarn duct rotates, owing to the action of the swirl airflow, and twists the fiber bundle in the processing duct, hence generating a source of yarn. The fiber suction force takes a distribution with a peak against the supplied air pressure and is independent of the exhaust air pressure. The fiber twist torque increases monotonously with supplied air pressure.

Experimental and Numerical Analysis of Droplet Cooling

2010 ◽  
Author(s):  
Paolo Tartarini ◽  
Mauro A. Corticelli ◽  
Paolo E. Santangelo
Keyword(s):  
Three Dimensional ◽  
Numerical Approach ◽  
Solid Substrate ◽  
Liquid Interface ◽  
Temperature Trend ◽  
Numerical Code ◽  
Uniform Mesh ◽  
Thermal Transient ◽  
Solid Liquid Interface ◽  
Solid Liquid

Dropwise cooling represents a major subject of interest for both academic and industrial researches. The present work is focused on investigating the thermal transient occurring as two water droplets are gently released (We &lt; 30) onto a heated solid surface. This latter has been kept at initial temperature lower than 373.15 K to analyze the single-phase-evaporation regime. To the purpose, both an experimental and a numerical approach have conveniently been employed. Infrared thermography has been used to evaluate the temperature trend at the solid-liquid interface: an experimental facility has been built to carry out measurements from below, thus realizing a fully non-intrusive approach. A transparent-crystal disk has been inserted to serve as the solid substrate; its upper surface has been painted by a black coating, thus providing a black-body surface as the solid-liquid interface. The infrared thermocamera has been placed below and perpendicular to that surface; temperature has been thereby measured, being emissivity a known parameter. A numerical code has been developed to predict the involved physical phenomena: temperature trend, evaporation time and evaporated flux result from discretizing the three-dimensional energy-diffusion equation by the finite-volume method. Moreover, the model is based on structured non-uniform mesh to adapt to the occurring temperature gradients. Very good agreement is shown between experimental and numerical outcomes in terms of thermal transient and recovery.

An Eddy-Resolving Reynolds Stress Model for the Turbulent Bubbly Flow in a Square Cross-Sectioned Bubble Column

2014 ◽  
Author(s):  
Matthias Ullrich ◽  
Benjamin Krumbein ◽  
Robert Maduta ◽  
Suad Jakirlić
Keyword(s):  
Reynolds Stress ◽  
Bubble Column ◽  
Bubbly Flow ◽  
Three Dimensional ◽  
Reynolds Stress Model ◽  
Moment Closure ◽  
Numerical Code ◽  
Stress Model ◽  
Mean Flow ◽  
Second Moment Closure

An instability-sensitive, eddy-resolving Reynolds Stress Model of turbulence, employed in the Eulerian-Eulerian two-fluid framework, is formulated and validated by computing the gas-liquid bubble column in a three-dimensional square cross-sectioned configuration in the homogeneous flow regime. Interphase momentum transfer is modelled by considering drag, lift and virtual mass forces. The turbulence in the continuous liquid phase is captured by using a Second-Moment Closure model employed in the Unsteady Reynolds-Averaged Navier Stokes framework implying the solving of the differential transport equations for the Reynolds stress tensor and the homogeneous part of the inverse turbulent time scale ωh. This uiuj – ωh model is appropriately extended in accordance with the Scale-Adaptive Simulation proposal, enabling so the development of the fluctuating turbulence. The results obtained are analysed along with a reference experiment with respect to the evolution of the mean flow and turbulent quantities in both gas and liquid phases. The model described is implemented in the numerical code OpenFOAM.

Bubble Behavior at an Uneven Wall

2016 ◽  
Author(s):  
H. Shmueli ◽  
G. Ziskind ◽  
R. Letan
Keyword(s):  
Bubble Growth ◽  
Three Dimensional ◽  
Grid Method ◽  
Numerical Code ◽  
Interface Tracking ◽  
Bubble Behavior ◽  
Three Dimensional Model ◽  
Surface Geometry ◽  
Initial State ◽  
Channel Orientation

The present study deals with single bubble growth on an uneven wall. A model problem is defined and solved using a three-dimensional numerical simulation. The wall has the shape of a triangular cavity and feature vortices. The equations solved in the present study are based on macro region modelling of the bubble alone and describe its growth from the initial state to detachment from the surface and consequent motion. The model includes a simultaneous solution of conservation equations for the liquid and gaseous phases, in conjunction with three-dimensional interface tracking. The latter is achieved using the level-set method. The numerical modeling includes the multi-grid method. The complete three-dimensional model is discretized using an original in-house numerical code realized in MATLAB. Different cases of bubble growth on the triangular cavity walls are investigated. The main conclusion from the calculations is that the bubble shape and its growth rate strongly depend on its location and on the channel orientation. New features, not possible for flat walls and special for this case, are revealed and discussed. It is demonstrated that under certain conditions, the bubble is obstructed by the surface geometry. It is also shown how a growing bubble affects the flow field inside a cavity, interacting with the vortex structure.

Calculation of External and Internal Transonic Flow Field of a Three-Dimensional S-Shaped Inlet

1985 ◽  
Author(s):  
Shen Huili ◽  
Luo Shijun ◽  
Ji Minggang ◽  
Xing Zongwen ◽  
Zhu Xin ◽  
...  
Keyword(s):  
Finite Difference ◽  
Flow Field ◽  
Transonic Flow ◽  
Present Method ◽  
Velocity Potential ◽  
Free Stream ◽  
Three Dimensional ◽  
Finite Difference Schemes ◽  
Finite Difference Equations ◽  
Free Stream Mach Number

A mixed finite difference method for calculating the external and internal transonic flow field around an s-shaped inlet is presented. Starting from the velocity potential equation and using Cartesian mesh and mixed finite difference schemes, the authors have obtained a system of finite difference equations and solved them with the aid of alternating line relaxations along two directions. Computations have been made for an s-shaped inlet with free stream Mach number M=0.8 at different angles of attack. Computed results are compared with those computed by perturbation method and with experimental results. Such a comparison shows that the present method is promising.

AN APPROACH TO FREELY COMBINING 3D DISCRETE AND FINITE ELEMENT METHODS

2013 ◽  
Vol 11 (01) ◽  
pp. 1350051 ◽  
Author(s):  
WEI GAO ◽  
MENGYAN ZANG ◽  
WEI XU
Keyword(s):  
Finite Element ◽  
Local Search ◽  
Function Method ◽  
Three Dimensional ◽  
Numerical Code ◽  
Rigid Sphere ◽  
Penalty Function Method ◽  
Dynamic Force ◽  
Vibration Process ◽  
Force Calculation

A freely combined three-dimensional (3D) discrete and finite element (FE) algorithm is developed. The algorithm, which is based on the method combining the discrete element (DE) and the corresponding node of the FE proposed by Lei and Zang, treats each combined point on the facet of the FE as the corresponding node of the method. This new algorithm includes global search, local search and the combined force calculation processes. The combined force between the DE and FE is processed by using a penalty function method. Following that, the corresponding numerical code is implemented into the in-house developed code, a dynamic explicit DE/FE code named CDFP. To test the accuracy of the proposed algorithm and the corresponding numerical code, the vibration process of two beams under dynamic force and the vibration process of two glass plates under impact of rigid sphere are simulated in elastic range. By comparing the results with those calculated by using LS-DYNA, it is shown that they agree with each other very well.

scholarly journals Numerical simulations of sunspots

2006 ◽  
Vol 2 (S239) ◽  
pp. 507-509
Author(s):  
G. J. J. Botha ◽  
A. M. Rucklidge ◽  
N. E. Hurlburt
Keyword(s):  
Convection Zone ◽  
Three Dimensional ◽  
Mhd Equations ◽  
Numerical Code ◽  
Axisymmetric Solution ◽  
Solar Convection Zone ◽  
Solar Convection ◽  
Linear Evolution ◽  
Compressible Mhd Equations ◽  
Parameter Values

AbstractThe origin, structure and evolution of sunspots are investigated using a numerical model. The compressible MHD equations are solved with physical parameter values that approximate the top layer of the solar convection zone. A three dimensional (3D) numerical code is used to solve the set of equations in cylindrical geometry, with the numerical domain in the form of a wedge. The linear evolution of the 3D solution is studied by perturbing an axisymmetric solution in the azimuthal direction. Steady and oscillating linear modes are obtained.

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