3,076 research outputs found
A Second Order Fully-discrete Linear Energy Stable Scheme for a Binary Compressible Viscous Fluid Model
We present a linear, second order fully discrete numerical scheme on a
staggered grid for a thermodynamically consistent hydrodynamic phase field
model of binary compressible fluid flow mixtures derived from the generalized
Onsager Principle. The hydrodynamic model not only possesses the variational
structure, but also warrants the mass, linear momentum conservation as well as
energy dissipation. We first reformulate the model in an equivalent form using
the energy quadratization method and then discretize the reformulated model to
obtain a semi-discrete partial differential equation system using the
Crank-Nicolson method in time. The numerical scheme so derived preserves the
mass conservation and energy dissipation law at the semi-discrete level. Then,
we discretize the semi-discrete PDE system on a staggered grid in space to
arrive at a fully discrete scheme using the 2nd order finite difference method,
which respects a discrete energy dissipation law. We prove the unique
solvability of the linear system resulting from the fully discrete scheme. Mesh
refinements and two numerical examples on phase separation due to the spinodal
decomposition in two polymeric fluids and interface evolution in the gas-liquid
mixture are presented to show the convergence property and the usefulness of
the new scheme in applications
On two-dimensional finite amplitude electro-convection in a dielectric liquid induced by a strong unipolar injection
The hydrodynamic stability of a dielectric liquid subjected to strong unipolar injection is numerically investigated. We determined the linear criterion Tc (T being the electric Rayleigh number) and finite amplitude one Tf over a wide range of the mobility parameter M. A noticeable discrepancy is shown for Tf between our numerical prediction and the value predicted by stability analysis, which is due to the velocity field used in stability analysis. Recent studies revealed a transition of the flow structure from one cell to two with an increase in T. We demonstrate that this transition results in a new subcritical bifurcationMinisterio de Ciencia y Tecnología FIS2011-25161Junta de Andalucía P10-FQM-5735Junta de Andalucía P09-FQM-458
Simulating water-entry/exit problems using Eulerian-Lagrangian and fully-Eulerian fictitious domain methods within the open-source IBAMR library
In this paper we employ two implementations of the fictitious domain (FD)
method to simulate water-entry and water-exit problems and demonstrate their
ability to simulate practical marine engineering problems. In FD methods, the
fluid momentum equation is extended within the solid domain using an additional
body force that constrains the structure velocity to be that of a rigid body.
Using this formulation, a single set of equations is solved over the entire
computational domain. The constraint force is calculated in two distinct ways:
one using an Eulerian-Lagrangian framework of the immersed boundary (IB) method
and another using a fully-Eulerian approach of the Brinkman penalization (BP)
method. Both FSI strategies use the same multiphase flow algorithm that solves
the discrete incompressible Navier-Stokes system in conservative form. A
consistent transport scheme is employed to advect mass and momentum in the
domain, which ensures numerical stability of high density ratio multiphase
flows involved in practical marine engineering applications. Example cases of a
free falling wedge (straight and inclined) and cylinder are simulated, and the
numerical results are compared against benchmark cases in literature.Comment: The current paper builds on arXiv:1901.07892 and re-explains some
parts of it for the reader's convenienc
Entropy-Production-Rate-Preserving Algorithms for Thermodynamically Consistent Nonisothermal Models of Incompressible Binary Fluids
We derive a thermodynamically consistent, non-isothermal, hydrodynamic model
for incompressible binary fluids following the generalized Onsager principle
and Boussinesq approximation. This model preserves not only the volume of each
fluid phase but also the positive entropy production rate under
thermodynamically consistent boundary conditions. Guided by the thermodynamical
consistency of the model, a set of second order structure-preserving numerical
algorithms are devised to solve the governing partial differential equations
along with consistent boundary conditions in the model, which preserve the
entropy production rate as well as the volume of each fluid phase at the
discrete level. Several numerical simulations are carried out using an
efficient adaptive time-stepping strategy based on one of the
structure-preserving schemes to simulate the Rayleigh-B\'{e}nard convection in
the binary fluid and interfacial dynamics between two immiscible fluids under
competing effects of the temperature gradient, gravity, and interfacial forces.
Roll cell patterns and thermally induced mixing of binary fluids are observed
in a rectangular region with insulated lateral boundaries and vertical ones
with imposed temperature difference. Long time simulations of interfacial
dynamics are performed demonstrating robust results of new structure-preserving
schemes
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