Ashraf Balabel

CMES-Computer Modeling in Engineering & Sciences, Vol.83, No.6, pp. 599-638, 2012, DOI:10.3970/cmes.2012.083.599

Abstract In the present paper, a new generalized level set numerical method based on the Fast Marching Method is developed for predicting the moving interface thermo-fluid dynamics in turbulent free surface flows. The numerical method is devoted to predict the turbulent interfacial dynamics resulting from either aerodynamic force or thermocapillary effects. The unsteady Reynolds averaged Navier-Stokes equations (RANS) and energy equation are coupled with the level set method and solved separately in each phase using the finite volume method on a non-staggered grid system. The application of the fast marching technique enables the fast as well as the accurate transport of… More >

J. Bonilla¹, L.J. Yebra¹, S. Dormido²

CMES-Computer Modeling in Engineering & Sciences, Vol.67, No.1, pp. 13-38, 2010, DOI:10.3970/cmes.2010.067.013

Abstract This paper presents and discusses a mean densities method applied to a steam-water two-phase flow mathematical model which uses a finite volume method and a staggered grid for discretizing a rigid volume in control volumes, where the thermodynamic properties are calculated. This method is based on the concepts of uniform pressure among all the control volumes and mean density in each control volume, allowing smooth thermodynamic properties, hence avoiding discontinuity at phase boundaries. This method wipes out the chattering problem due to the continuous and differentiable modelling of density and its partial derivatives, which leads to faster simulations and increases… More >

S. Aland¹, J. Lowengrub², A. Voigt¹

CMES-Computer Modeling in Engineering & Sciences, Vol.57, No.1, pp. 77-108, 2010, DOI:10.3970/cmes.2010.057.077

Abstract We present a new method for simulating two-phase flows in complex geometries, taking into account contact lines separating immiscible incompressible components. We combine the diffuse domain method for solving PDEs in complex geometries with the diffuse-interface (phase-field) method for simulating multiphase flows. In this approach, the complex geometry is described implicitly by introducing a new phase-field variable, which is a smooth approximation of the characteristic function of the complex domain. The fluid and component concentration equations are reformulated and solved in larger regular domain with the boundary conditions being implicitly modeled using source terms. The method is straightforward to implement… More >

Hossein M. Shodja^1,2,3, Alireza Hashemian^1,4

CMES-Computer Modeling in Engineering & Sciences, Vol.32, No.1, pp. 17-34, 2008, DOI:10.3970/cmes.2008.032.017

Abstract Gradient reproducing kernel particle method (GRKPM) is a meshless technique which incorporates the first gradients of the function into the reproducing equation of RKPM. Therefore, in two-dimensional space GRKPM introduces three types of shape functions rather than one. The robustness of GRKPM's shape functions is established by reconstruction of a third-order polynomial. To enforce the essential boundary conditions (EBCs), GRKPM's shape functions are modified by transformation technique. By utilizing the modified shape functions, the weak form of the nonlinear evolutionary Buckley-Leverett (BL) equation is discretized in space, rendering a system of nonlinear ordinary differential equations (ODEs). Subsequently, Gear's method is… More >

F. Bierbrauer, S.-P. Zhu¹

CMES-Computer Modeling in Engineering & Sciences, Vol.19, No.1, pp. 1-22, 2007, DOI:10.3970/cmes.2007.019.001

Abstract Recently the use of the one-field formulation in the numerical solution of the Navier-Stokes equations for two-phase incompressible flow has become a very attractive approach in CFD (computational fluid dynamics). While the presence of material discontinuities across fluid interfaces presents some difficulty, it is their combination with a non-solenoidal discontinuous initial velocity field, commonly occurring in the mathematical formulation, that has provided the greatest hindrance in the numerical solution. This paper presents three analytical solutions, the Bounded Creeping Flow, Solenoidal and Conserved Solenoidal Solutions, which are both continuous, incompressible, retain as much of the original mathematical formulation as possible and… More >

T. Uchiyama¹

FDMP-Fluid Dynamics & Materials Processing, Vol.7, No.4, pp. 371-388, 2011, DOI:10.3970/fdmp.2011.007.371

Abstract This study proposes a three-dimensional grid-free method to simulate particle-laden gas flows. It is based on a vortex method. The flow region is not resolved into computational grids, but the gas vorticity field is discretized by vortex elements. The behavior of the vortex element and the particle motion are simultaneously calculated by using the Lagrangian approach. Eight cubic cells are locally allocated around each particle to compute the effect of the particle motion on the gas flow. In each cell, the change in the vorticity due to the particle is calculated, and it is considered by generating a vortex element… More >

B. Madani¹, F. Topin², L. Tadrist²

FDMP-Fluid Dynamics & Materials Processing, Vol.6, No.4, pp. 351-368, 2010, DOI:10.3970/fdmp.2010.006.351

Abstract The present work deals with the hydraulic characterization of two-phase flow with phase change in a channel filled with metallic foam. We provide a general presentation of metallic foams including morphological characteristics, fabrication processes and industrial applications. The experimental facility, which consists of a hydrodynamic loop, the test section, measurement devices, and the data acquisition system, is presented. The Metallic foam sample tested in the present work is manufactured by SCPS (French manufacturer). N-pentane is used as a coolant fluid. The mass velocity values lie between 4 and 49 kg/ m2s, while the heating power in the test section ranges… More >

Yu. Gaponenko¹, I. Ryzhkov², V. Shevtsova³

FDMP-Fluid Dynamics & Materials Processing, Vol.6, No.1, pp. 75-98, 2010, DOI:10.3970/fdmp.2010.006.075

Abstract Gas-liquid flows in annulus are analyzed for fluids in large range of viscosity ratios. The geometry corresponds to a liquid bridge co-axially placed into an outer cylinder with solid walls. The internal core consists of solid rods at the bottom and top, while the central part is a relatively short liquid zone filled with viscous liquid and kept in its position by surface tension. The gas enters into the annular duct and entrains initially quiescent liquid. The flow structures in the liquid and gas are obtained numerically for different shapes of solid rods. Solution for fully developed flow in annulus… More >

A. Alke¹, D. Bothe¹

FDMP-Fluid Dynamics & Materials Processing, Vol.5, No.4, pp. 345-372, 2009, DOI:10.3970/fdmp.2009.005.345

Abstract We present a computational approach based on the Volume-of-Fluid (VOF) method for simulating the influence of a soluble surfactant on the behavior of two-phase systems with deformable interface. Our approach is applicable to diffusion controlled processes, where the relation between the area-specific excess surfactant concentration on the interface and the volume-specific concentration adjacent to the interface is given by an adsorption isotherm. Main issues of the numerical model are an extended surface transport theorem used for describing the interfacial flux and an iso-surface of the VOF-variable used as a connected approximation for the interface. 3D-simulations of a bubble moving through… More >

Huawei Han¹, Kamiel S. Gabriel²

FDMP-Fluid Dynamics & Materials Processing, Vol.2, No.4, pp. 287-298, 2006, DOI:10.3970/fdmp.2006.002.287

Abstract Data on air-water co-current two-phase annular flow in a tube with an inner diameter of 9.525 mm (3/8 in) were previously collected at both microgravity u-g and normal gravity (1-g) conditions. The data contained measurements of pressure drop, in addition to previously published data of liquid film thickness. This paper presents the results and analysis of the influence of flow pressure gradient on interfacial wave properties of annular flow at both microgravity and normal gravity. The examined wave properties include wave base thickness, wave height (or roughness height), wave spacing, wave speed and wave frequency. It was found that, the… More >