Brahim Mahfoud¹, Rachid Bessaih^1,2

FDMP-Fluid Dynamics & Materials Processing, Vol.8, No.1, pp. 1-26, 2012, DOI:10.3970/fdmp.2011.008.001

Abstract Oscillatory swirling flows in a cylindrical enclosure, having aspect ratio (height/radius) γ=2, filled with a liquid metal, and submitted to a destabilizing vertical temperature gradient (system heated from below) is investigated by means of direct numerical solution of the governing (continuity, radial and axial momentum,swirlandenergy)equations. The bottom and top disks are assumed to rotate at equal (co-rotating) and opposite (counter-rotating) angular velocities. The critical Reynoldsnumber,Re_cr and the critical frequency of oscillations, F_cr arecalculated as a function of the Richardson number, Ri, ranging between 0 and 4. Stability diagrams are presented, reflecting the results of the numerical investigation, which put in… More >

Md. Tofiqul Islam¹, Sumon Saha², Md. Arif Hasan Mamun³, Mohammad Ali⁴

FDMP-Fluid Dynamics & Materials Processing, Vol.4, No.2, pp. 125-138, 2008, DOI:10.3970/fdmp.2008.004.125

Abstract A numerical study has been performed on mixed convection inside an open cavity on the bottom of a channel. One of the three walls of the cavity experiences a uniform heat flux while the other walls and the top of the channel are adiabatic. Three different cases are considered by applying uniform heat flux on (a) the inflow side (assisting forced flow); (b) the outflow side (opposing forced flow); (c) the bottom horizontal surface (transverse flow). The Galerkin weighted residual method of finite element formulation is used to discretize the governing equations. For mixed convection, the influential parameters are the… More >

U. Schoisswohl¹, H. C. Kuhlmann²

FDMP-Fluid Dynamics & Materials Processing, Vol.3, No.4, pp. 317-328, 2007, DOI:10.3970/fdmp.2007.003.317

Abstract The flow in thermocapillary liquid pools heated or cooled from above can exhibit various flow patterns depending on the thermal conditions and the geometrical constraints. This pattern formation and the respective physical mechanisms are studied numerically by means of a linear-stability analysis. We focus on the transition from the steady axisymmetric to a three-dimensional flow. More >

Rodica Borcia^1,2, Michael Bestehorn²

FDMP-Fluid Dynamics & Materials Processing, Vol.3, No.4, pp. 287-294, 2007, DOI:10.3970/fdmp.2007.003.287

Abstract We developed a phase field model for Marangoni convection in compressible fluids of van der Waals type far from criticality. The theoretical description is based on the Navier-Stokes equation with extra terms responsible for describing the Marangoni effect, the classical heat equation, and the continuity equation. The model previously developed for a two-layer geometry is now extended to drops and bubbles. Finally, we report on 2D numerical simulations for drop Marangoni migration in a vertical temperature gradient. More >

H. Tang¹, L.C. Wrobel², Z. Fan²

FDMP-Fluid Dynamics & Materials Processing, Vol.3, No.2, pp. 129-146, 2007, DOI:10.3970/fdmp.2007.003.129

Abstract This paper presents an overview of diverse extrusion techniques and, in particular, a focused discussion about the rheoextrusion process for semi-solid casting (a novel casting process for the fabrication of high quality metals). The review reveals a wealth of interesting rheological and microstructural features, illustrating qualitative and quantitative data. The analysis is supported by relevant numerical results and examples. It is shown how numerical studies can lead to significant insights into these processes by providing more detailed information on the fundamental mechanisms of morphology development (during phase change) and profile forming. The die filling and solidification behaviours within extrusion dies… More >

A.K. Plappally¹, M.A.R. Sharif¹, R.C. Bradt²

FDMP-Fluid Dynamics & Materials Processing, Vol.3, No.2, pp. 115-128, 2007, DOI:10.3970/fdmp.2007.003.115

Abstract A novel physical chemical filtration process in a tundish for removal of inclusion particles from molten steel is proposed and analyzed. The considered inclusion particles are mainly composed of the minerals alumina (Al2O3 and spinel (MgAl2O4, which have an affinity to adhere (on contact) to an inclusion trap. An industrial tundish is considered and modified with a zigzag channel block insert installed across the molten steel flow so that when the molten steel flows through the zigzag channels, the inclusion particles are driven into contact with the channel surfaces by increased recirculation and turbulence. The inclusions will bond with the… More >

Evgeny V. Votyakov¹, Egbert A. Zienicke¹

FDMP-Fluid Dynamics & Materials Processing, Vol.3, No.2, pp. 97-114, 2007, DOI:10.3970/fdmp.2007.003.097

Abstract We simulated numerically the laminar flow in the geometry and the magnetic field of the experimental channel used in [Andreev, Kolesnikov, and Thess (2006)]. This provides detailed information about the electric potential distribution for the laminar regime (numerical simulation) and in the turbulent regime as well (experiment). As follows from comparison of simulated and experimental results, the flow under the magnet is determined by the interaction parameter N = Ha² / Re representing the ratio between magnetic force, determined by the Hartmann number Ha, and inertial force, determined by the Reynolds number Re. We compared two variants: (i)(Re,N)=(2000,18.6) (experiment), (400,20.25)… More >

Xiaofeng Yang¹, Ashley J. James^1,2

FDMP-Fluid Dynamics & Materials Processing, Vol.3, No.1, pp. 65-96, 2007, DOI:10.3970/fdmp.2007.003.065

Abstract An arbitrary Lagrangian-Eulerian (ALE) method for interfacial flows with insoluble surfactants is presented. The interface is captured using a coupled level set and volume of fluid method, which takes advantage of the strengths of both the level set method and the volume of fluid method. By directly tracking the surfactant mass, the method conserves surfactant mass, and prevents surfactant from diffusing off the interface. Interfacial area is also tracked. To accurately approximate the interfacial area, the fluid interface is reconstructed using piece-wise parabolas. The surfactant concentration, which determines the local surface tension through an equation of state, is then computed… More >

Jacek Narski^1,2, Marco Picasso¹

FDMP-Fluid Dynamics & Materials Processing, Vol.3, No.1, pp. 49-64, 2007, DOI:10.3970/fdmp.2007.003.049

Abstract An adaptive phase field model for the solidification of binary alloys in three space dimensions is presented. The fluid flow in the liquid due to different liquid/solid densities is taken into account. The unknowns are the phase field, the alloy concentration and the velocity/pressure in the liquid. Continuous, piecewise linear finite elements are used for the space discretization, a semi-implicit scheme is used for time discretization. An adaptive method allows the number of degrees of freedom to be reduced, the mesh tetrahedrons having high aspect ratio whenever needed. Numerical results show that our method is effective and allows to perform… More >

Mark Sussman¹, Mitsuhiro Ohta²

FDMP-Fluid Dynamics & Materials Processing, Vol.3, No.1, pp. 21-36, 2007, DOI:10.3970/fdmp.2007.003.021

Abstract In this paper, we describe new techniques for numerically approximating two-phase flows. Specifically, we present new techniques for treating the viscosity and surface tension terms that appear in the Navier-Stokes equations for incompressible two-phase flow. Our resulting numerical method has the property that results computed using our two-phase algorithm approach the corresponding "one-phase'' algorithm in the limit of zero gas density/viscosity; i.e. the two-phase results approach the one-phase free-boundary results in the limit that the gas is assumed to become a uniform pressure void. By grid convergence checks and comparison with previous experimental data, we shall demonstrate the advantages of… More >