58,293 research outputs found
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
Exclusive neutrino-production of a charmed meson
We calculate the leading order in QCD amplitude for exclusive
neutrino and antineutrino production of a pseudoscalar charmed meson on an
unpolarized nucleon. We work in the framework of the collinear QCD approach
where generalized parton distributions (GPDs) factorize from perturbatively
calculable coefficient functions. We include both terms in the
coefficient functions and mass term contributions in the heavy meson
distribution amplitudes. We emphasize the sensitivity of specific observables
on the transversity quark GPDs.Comment: 17 pages,16 figures. Version 2, to be published in Phys Rev D,
misprint corrected in unnumbered equation after eq.43, plots corrected after
numerical bug repaire
Hard exclusive neutrino production of a light meson
We update the leading order in QCD amplitude for deep exclusive
neutrino and antineutrino production of a light meson on an unpolarized
nucleon. The factorization theorems of the collinear QCD approach allow us to
write the amplitude as the convolution of generalized parton distributions
(GPDs) and perturbatively calculable coefficient functions. We study both the
pseudoscalar meson and longitudinally polarized vector meson cases. It turns
out that, contrarily to the electroproduction case, the leading twist
scattering amplitudes for and productions are proportional to
one another, which may serve as an interesting new test of the leading twist
dominance of exclusive processes at medium scale. The dominance of the gluonic
contribution to most cross sections is stressed.Comment: 9 pages, 8 figures. second version (to be published in Phys Rev D):
misprint in name of second author corrected; one added reference; minor
misprints corrected. arXiv admin note: text overlap with arXiv:1702.0031
Pressure-control purge panel for automatic butt welding
Modification of a purge panel for use in an automatic butt weld reduces the drop in pressure between the regulators and the weld head and tube purge fitting. The invention affects air regulators for plants, regulating circuits for pneumatic valves, and automatic welding machines
On timelike and spacelike hard exclusive reactions
We show to next-to-leading order accuracy in the strong coupling alpha_s how
the collinear factorization properties of QCD in the generalized Bjorken regime
relate exclusive amplitudes for spacelike and timelike hadronic processes. This
yields simple space--to--timelike relations linking the amplitudes for
electroproduction of a photon or meson to those for photo- or meso-production
of a lepton pair. These relations constitute a new test of the relevance of
leading twist analyzes of experimental data.Comment: v2: major text revision; results, references, and author added; v3:
matches the published version Phys. Rev. D86, rapid communication
Coolant passage heat transfer with rotation
In current and advanced gas turbine engines, increased speeds, pressures and temperatures are used to reduce specific fuel consumption and increase thrust/weight ratios. Hence, the turbine airfoils are subjected to increased heat loads escalating the cooling requirements to satisfy life goals. The efficient use of cooling air requires that the details of local geometry and flow conditions be adequately modeled to predict local heat loads and the corresponding heat transfer coefficients. The objective of this program is to develop a heat transfer and pressure drop data base, computational fluid dynamic techniques and correlations for multi-pass rotating coolant passages with and without flow turbulators. The experimental effort is focused on the simulation of configurations and conditions expected in the blades of advanced aircraft high pressure turbines. With the use of this data base, the effects of Coriolis and buoyancy forces on the coolant side flow can be included in the design of turbine blades
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