Browsing by Author "Azaiez, J."
Now showing 1 - 2 of 2
Results Per Page
Sort Options
- ItemOpen AccessDynamics of viscous liquid bridges inside microchannels subject to external oscillatory flows(Physical Review E, 2015-02) Chen, Zhangxing (John); Ahmadlouydarab, M.; Azaiez, J.We report on two-dimensional simulations of liquid bridges' dynamics inside microchannels of uniform wettability and subject to an external oscillatory flow rate. The oscillatory flow results in a zero net flow rate and its effects are compared to those of a stationary system. To handle the three phase contact lines motion, Cahn-Hilliard diffuse-interface formulation was used and the flow equations were solved using the finite element method with adaptively refined unstructured grids. The results indicate that the liquid bridge responds in three different ways depending on the substrate wettability properties and the frequency of the oscillatory flow. In particular below a critical frequency, the liquid bridge will rupture when the channel walls are philic or detach from the surface when they are phobic. However, at high frequencies, the liquid bridge shows a perpetual periodic oscillatory motion for both philic and phobic surfaces. Furthermore, an increase in the frequency of the flow velocity results in stabilization effects and a behavior approaching that of the stationary system where no rupture or detachment can be observed. This stable behavior is the direct result of less deformation of the liquid bridge due to the fast flow direction change and motion of contact lines on the solid substrate. Moreover, it was found that the flow velocity is out of phase with the footprint and throat lengths and that the latter two also show a phase difference. These differences were explained in terms of the motion of the two contact lines on the solid substrates and the deformation of the two fluid-fluid interfaces.
- ItemOpen AccessNumerical Simulations of Gravity Driven Reversible Reactive Flows in Homogeneous Porous Media(2015-06-29) Alhumade, H.; Azaiez, J.The effect of reversibility on the instability of a miscible vertical reactive flow displacement is examined. A model, where densities and/or viscosities mismatches between the reactants and the chemical product trigger instability, is adopted. The problem is governed by the continuity equation, Darcy’s law, and the convection-diffusion-reaction equations. The problem is formulated and solved numerically using a combination of the highly accurate spectral methods based on Hartley’s transform and the finite-difference technique. Nonlinear simulations were carried out for a variety of parameters to analyse the effects of the reversibility of the chemical reaction on the development of the flow under different scenarios of the frontal instability. In general, faster attenuation in the development and growth of the instability is reported as the reversibility of the chemical reaction increases. However, it was observed that reversibility is capable of triggering instability for particular choices of the densities and viscosities mismatches. In addition, the effect of the reversibility in enhancing the instability was illustrated by presenting the total relative contact area between the reactants and the product.