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 More >

H. Chanson¹, K.K. Tan²

FDMP-Fluid Dynamics & Materials Processing, Vol.7, No.4, pp. 403-418, 2011, DOI:10.3970/fdmp.2011.007.403

Abstract A tidal bore is a wall of water propagating upstream as the tidal flow turns to rising into an estuary with a tidal range larger than 5 to 6 m and the bathymetry that amplifies the tidal wave. The bore front is a shock characterised by a singularity of the free-surface and pressure and velocity fields. This study aims to characterise the impact of tidal bores on the turbulent dispersion of fish eggs. Some physical modelling was performed based upon a Froude similitude and the tracking of plastic beads acting as fish egg proxies was More >

M. Do-Quang¹, A. Carlson¹, G. Amberg¹

FDMP-Fluid Dynamics & Materials Processing, Vol.7, No.4, pp. 389-402, 2011, DOI:10.3970/fdmp.2011.007.389

Abstract Inkjet technology has been recognized as one of the most successful and promising micro-system technologies. The wide application areas of printer heads and the increasing demand of high quality prints are making ink consumption and print see-through important topics in the inkjet technology. In the present study we investigate numerically the impact of ink droplets onto a porous material that mimics the paper structure. The mathematical framework is based on a free energy formulation, coupling the Cahn-Hilliard and Navier Stokes equations, for the modelling of the two-phase flow. The case studied here consists of a 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… More >

Y.Q. He, Q.C. Bi¹, D.X. Shi¹

FDMP-Fluid Dynamics & Materials Processing, Vol.7, No.4, pp. 357-370, 2011, DOI:10.3970/fdmp.2011.007.357

Abstract The behavior of a single air bubble rising in magnetic fluids without magnetic fields is visualized using a mini-gap between two parallel vertical glass plates. Water-based Fe3O4 magnetic fluids with particle volume concentration of 6.33 % and density 1261.96 kgm - 3 are filled in these gaps and a single air bubble is produced through the orifice at the bottom of the gap. The thicknesses of the gaps are 1 and 2 mm, respectively. Diameters of the orifices are 0.64 and 1.02 mm for 1 mm gap, and 0.64, 1.02 and 1.6 mm for 2… More >

J.J. Derksen¹, D. Eskin²

FDMP-Fluid Dynamics & Materials Processing, Vol.7, No.4, pp. 341-356, 2011, DOI:10.3970/fdmp.2011.007.341

Abstract Direct simulations of laminar solid-liquid flow in micro-channels with full resolution of the solid-liquid interfaces have been performed. The solids phase consists of simple agglomerates, assembled of monosized, spherical particles. The flow of the interstitial liquid is solved with the lattice-Boltzmann method. Solids and fluid dynamics are two-way coupled. The simulations keep track of the flow-induced forces in the agglomerates. The effects of agglomerate type (doublets, triplets, and quadruplets), solids loading, and channel geometry on (the statistics of the) flow and collision-induced forces have been investigated. By comparing these forces with agglomerate strength, we would More >

T. Sanada¹, K. Ando², T. Colonius²

FDMP-Fluid Dynamics & Materials Processing, Vol.7, No.4, pp. 329-340, 2011, DOI:10.3970/fdmp.2011.007.329

Abstract When a droplet impacts a solid surface at high speed, the contact periphery expands very quickly and liquid compressibility plays an important role in the initial dynamics and the formation of lateral jets. The high speed impact results in high pressures that can account for the surface erosion. In this study, we numerically investigated a high speed droplet impacts on a solid wall. The multicomponent Euler equations with the stiffened equation of state are computed using a FV-WENO scheme with an HLLC Riemann solver that accurately captures shocks and interfaces. In order to compare the More >

Malcolm R. Davidson¹, Dalton J.E. Harvie¹

FDMP-Fluid Dynamics & Materials Processing, Vol.7, No.3, pp. 317-328, 2011, DOI:10.3970/fdmp.2011.007.317

Abstract A volume-of-fluid numerical method, adapted by the authors [Harvie, Cooper-White and Davidson (2008)] to simulate the flow of viscoelastic fluids, is used to predict deformation of a viscoelastic droplet carried by an immiscible Newtonian liquid through an axisymmetric microfluidic contraction-expansion. Values of the capillary number and elasticity number are chosen based on corresponding values for a rectangular contraction for which a reentrant cavity at the rear of the drop and subsequent encapsulation behaviour was observed experimentally by Harvie, Cooper-White and Davidson (2008). A reentrant cavity, similar to the observed one, is predicted; however, encapsulation is More >

D. Bothe^1,2, M. Kröger¹, H.-J. Warnecke³

FDMP-Fluid Dynamics & Materials Processing, Vol.7, No.3, pp. 303-316, 2011, DOI:10.3970/fdmp.2011.007.303

Abstract In this paper numerical results on reactive mass transfer from single gas bubbles to a surrounding liquid are presented. The underlying numerical method is based on the solution of the incompressible two-phase Navier-Stokes equations. The Volume-of-Fluid method is applied for the description of the liquid-gas interface. Within the numerical approach the concentration of the transfer component is represented by two separate variables, one for each phase. Numerical results are in good agreement with experimental data. More >

Carole Planchette¹, Elise Lorenceau¹, Günter Brenn²

FDMP-Fluid Dynamics & Materials Processing, Vol.7, No.3, pp. 279-302, 2011, DOI:10.3970/fdmp.2011.007.279

Abstract This work is dedicated to a general description of collisions between two drops of immiscible liquids. Our approach is mainly experimental and allows us to describe the outcomes of such collisions according to a set of relevant parameters. Varying the relative velocity U as well as the impact parameter X we can build for each pair of investigated liquids a nomogram X,U showing three possible regimes: coalescence, head-on separation and off-center separation. In this paper, we also study the influence of the liquid properties, i.e. viscosity, density, surface and interfacial tensions using a set of… More >