6,582 research outputs found
An efficient second order in time scheme for approximating long time statistical properties of the two dimensional Navier-Stokes equations
We investigate the long tim behavior of the following efficient second order
in time scheme for the 2D Navier-Stokes equation in a periodic box:
\frac{3\omega^{n+1}-4\omega^n+\omega^{n-1}}{2k} +
\nabla^\perp(2\psi^n-\psi^{n-1})\cdot\nabla(2\omega^n-\omega^{n-1}) -
\nu\Delta\omega^{n+1} = f^{n+1}, \quad -\Delta \psi^n = \om^n. The scheme is
a combination of a 2nd order in time backward-differentiation (BDF) and a
special explicit Adams-Bashforth treatment of the advection term. Therefore
only a linear constant coefficient Poisson type problem needs to be solved at
each time step. We prove uniform in time bounds on this scheme in \dL2,
\dH1 and provided that the time-step is sufficiently small.
These time uniform estimates further lead to the convergence of long time
statistics (stationary statistical properties) of the scheme to that of the NSE
itself at vanishing time-step. Fully discrete schemes with either Galerkin
Fourier or collocation Fourier spectral method are also discussed
A second order in time, uniquely solvable, unconditionally stable numerical scheme for Cahn-Hilliard-Navier-Stokes equation
We propose a novel second order in time numerical scheme for
Cahn-Hilliard-Navier- Stokes phase field model with matched density. The scheme
is based on second order convex-splitting for the Cahn-Hilliard equation and
pressure-projection for the Navier-Stokes equation. We show that the scheme is
mass-conservative, satisfies a modified energy law and is therefore
unconditionally stable. Moreover, we prove that the scheme is uncondition- ally
uniquely solvable at each time step by exploring the monotonicity associated
with the scheme. Thanks to the weak coupling of the scheme, we design an
efficient Picard iteration procedure to further decouple the computation of
Cahn-Hilliard equation and Navier-Stokes equation. We implement the scheme by
the mixed finite element method. Ample numerical experiments are performed to
validate the accuracy and efficiency of the numerical scheme
Quantum criticality in disordered bosonic optical lattices
Using the exact Bose-Fermi mapping, we study universal properties of
ground-state density distributions and finite-temperature quantum critical
behavior of one-dimensional hard-core bosons in trapped incommensurate optical
lattices. Through the analysis of universal scaling relations in the quantum
critical regime, we demonstrate that the superfluid to Bose glass transition
and the general phase diagram of disordered hard-core bosons can be uniquely
determined from finite-temperature density distributions of the trapped
disordered system.Comment: 4 pages, 5 figure
Existence and uniqueness of global weak solutions to a Cahn-Hilliard-Stokes-Darcy system for two phase incompressible flows in karstic geometry
We study the well-posedness of a coupled Cahn-Hilliard-Stokes-Darcy system
which is a diffuse-interface model for essentially immiscible two phase
incompressible flows with matched density in a karstic geometry. Existence of
finite energy weak solution that is global in time is established in both 2D
and 3D. Weak-strong uniqueness property of the weak solutions is provided as
well
Energy-Efficient Optimization for Wireless Information and Power Transfer in Large-Scale MIMO Systems Employing Energy Beamforming
In this letter, we consider a large-scale multiple-input multiple-output
(MIMO) system where the receiver should harvest energy from the transmitter by
wireless power transfer to support its wireless information transmission. The
energy beamforming in the large-scale MIMO system is utilized to address the
challenging problem of long-distance wireless power transfer. Furthermore,
considering the limitation of the power in such a system, this letter focuses
on the maximization of the energy efficiency of information transmission (bit
per Joule) while satisfying the quality-of-service (QoS) requirement, i.e.
delay constraint, by jointly optimizing transfer duration and transmit power.
By solving the optimization problem, we derive an energy-efficient resource
allocation scheme. Numerical results validate the effectiveness of the proposed
scheme.Comment: 4 pages, 3 figures. IEEE Wireless Communications Letters 201
- …