403,547 research outputs found
Macroscale boundary conditions for a non-linear heat exchanger
Multiscale modelling methodologies build macroscale models of materials with
complicated fine microscale structure. We propose a methodology to derive
boundary conditions for the macroscale model of a prototypical non-linear heat
exchanger. The derived macroscale boundary conditions improve the accuracy of
macroscale model. We verify the new boundary conditions by numerical methods.
The techniques developed here can be adapted to a wide range of multiscale
reaction-diffusion-advection systems
Thermodynamic consistency of liquid-gas lattice Boltzmann simulations
Lattice Boltzmann simulations have been very successful in simulating
liquid-gas and other multi-phase fluid systems. However, the underlying second
order analysis of the equation of motion has long been known to be insufficient
to consistently derive the fourth order terms that are necessary to represent
an extended interface. These same terms are also responsible for thermodynamic
consistency, i.e. to obtain a true equilibrium solution with both a constant
chemical potential and a constant pressure. In this article we present an
equilibrium analysis of non-ideal lattice Boltzmann methods of sufficient order
to identify those higher order terms that lead to a lack of thermodynamic
consistency. We then introduce a thermodynamically consistent forcing method.Comment: 12 pages, 8 figure
Design procedure for low-drag subsonic airfoils
Airfoil has least amount of drag under given restrictions of boundary layer transition position, lift coefficient, thickness ratio, and Reynolds number based on airfoil chord. It is suitable for use as wing and propeller aircraft sections operating at subsonic speeds and for hydrofoil sections and blades for fans, compressors, turbines, and windmills
Non-analyticity of the groud state energy of the Hamiltonian for Hydrogen atom in non-relativistic QED
We derive the ground state energy up to the fourth order in the fine
structure constant for the translation invariant Pauli-Fierz
Hamiltonian for a spinless electron coupled to the quantized radiation field.
As a consequence, we obtain the non-analyticity of the ground state energy of
the Pauli-Fierz operator for a single particle in the Coulomb field of a
nucleus
Ground state energy of unitary fermion gas with the Thomson Problem approach
The dimensionless universal coefficient defines the ratio of the
unitary fermions energy density to that for the ideal non-interacting ones in
the non-relativistic limit with T=0. The classical Thomson Problem is taken as
a nonperturbative quantum many-body arm to address the ground state energy
including the low energy nonlinear quantum fluctuation/correlation effects.
With the relativistic Dirac continuum field theory formalism, the concise
expression for the energy density functional of the strongly interacting limit
fermions at both finite temperature and density is obtained. Analytically, the
universal factor is calculated to be . The energy gap is
\Delta=\frac{{5}{18}{k_f^2}/(2m).Comment: Identical to published version with revisions according to comment
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