114 research outputs found
Generalized Navier Boundary Condition and Geometric Conservation Law for surface tension
We consider two-fluid flow problems in an Arbitrary Lagrangian Eulerian (ALE)
framework. The purpose of this work is twofold. First, we address the problem
of the moving contact line, namely the line common to the two fluids and the
wall. Second, we perform a stability analysis in the energy norm for various
numerical schemes, taking into account the gravity and surface tension effects.
The problem of the moving contact line is treated with the so-called
Generalized Navier Boundary Conditions. Owing to these boundary conditions, it
is possible to circumvent the incompatibility between the classical no-slip
boundary condition and the fact that the contact line of the interface on the
wall is actually moving. The energy stability analysis is based in particular
on an extension of the Geometry Conservation Law (GCL) concept to the case of
moving surfaces. This extension is useful to study the contribution of the
surface tension. The theoretical and computational results presented in this
paper allow us to propose a strategy which offers a good compromise between
efficiency, stability and artificial diffusion
Some qualitative properties of the solutions of the Magnetohydrodynamic equations for nonlinear bipolar fluids
In this article we study the long-time behaviour of a system of nonlinear
Partial Differential Equations (PDEs) modelling the motion of incompressible,
isothermal and conducting modified bipolar fluids in presence of magnetic
field. We mainly prove the existence of a global attractor denoted by \A for
the nonlinear semigroup associated to the aforementioned systems of nonlinear
PDEs. We also show that this nonlinear semigroup is uniformly differentiable on
\A. This fact enables us to go further and prove that the attractor \A is
of finite-dimensional and we give an explicit bounds for its Hausdorff and
fractal dimensions.Comment: The final publication is available at Springer via
http://dx.doi.org/10.1007/s10440-014-9964-
A mathematical model for unsteady mixed flows in closed water pipes
We present the formal derivation of a new unidirectional model for unsteady
mixed flows in non uniform closed water pipe. In the case of free surface
incompressible flows, the \FS-model is formally obtained, using formal
asymptotic analysis, which is an extension to more classical shallow water
models. In the same way, when the pipe is full, we propose the \Pres-model,
which describes the evolution of a compressible inviscid flow, close to gas
dynamics equations in a nozzle. In order to cope the transition between a free
surface state and a pressured (i.e. compressible) state, we propose a mixed
model, the \PFS-model, taking into account changes of section and slope
variation
Weak and strong solutions of equations of compressible magnetohydrodynamics
International audienceThis article proposes a review of the analysis of the system of magnetohydrodynamics (MHD). First, we give an account of the modelling asumptions. Then, the results of existence of weak solutions, using the notion of renormalized solutions. Then, existence of strong solutions in the neighbourhood of equilibrium states is reviewed, in particular with the method of Kawashima and Shizuta. Finally, the special case of dimension one is highlighted : the use of Lagrangian coordinates gives a simpler system, which is solved by standard techniques
Gating of aquaporins by heavy metals in Allium cepa L. epidermal cells
Changes in the water permeability, aquaporin (AQP) activity, of leaf cells were investigated in response to different heavy metals (Zn2+, Pb2+, Cd2+, Hg2+). The cell pressure probe experiments were performed on onion epidermal cells as a model system. Heavy metal solutions at different concentrations (0.05 μM–2 mM) were used in our experiments. We showed that the investigated metal ions can be arranged in order of decreasing toxicity (expressed as a decrease in water permeability) as follows: Hg>Cd>Pb>Zn. Our results showed that β-mercaptoethanol treatment (10 mM solution) partially reverses the effect of AQP gating. The magnitude of this reverse differed depending on the metal and its concentration. The time course studies of the process showed that the gating of AQPs occurred within the first 10 min after the application of a metal. We also showed that after 20–40 min from the onset of metal treatment, the water flow through AQPs stabilized and remained constant. We observed that irrespective of the metal applied, the effect of AQP gating can be recorded within the first 10 min after the administration of metal ions. More generally, our results indicate that the toxic effects of investigated metal ions on the cellular level may involve AQP gating
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