7,807 research outputs found
A second-order closure analysis of turbulent diffusion flames
A complete second-order closure computer program for the investigation of compressible, turbulent, reacting shear layers was developed. The equations for the means and the second order correlations were derived from the time-averaged Navier-Stokes equations and contain third order and higher order correlations, which have to be modeled in terms of the lower-order correlations to close the system of equations. In addition to fluid mechanical turbulence models and parameters used in previous studies of a variety of incompressible and compressible shear flows, a number of additional scalar correlations were modeled for chemically reacting flows, and a typical eddy model developed for the joint probability density function for all the scalars. The program which is capable of handling multi-species, multistep chemical reactions, was used to calculate nonreacting and reacting flows in a hydrogen-air diffusion flame
A Theory of the Pseudogap State of the Cuprates
The phase diagram for a general model for Cuprates is derived in a mean-field
approximation. A phase violating time-reversal without breaking translational
symmetry is possible when both the ionic interactions and the local repulsions
are large compared to the energy difference between the Cu and O
single-particle levels. It ends at a quantum critical point as the hole or
electron doping is increased. Such a phase is necessarily accompanied by
singular forward scattering such that, in the stable phase, the density of
states at the chemical potential, projected to a particular point group
symmetry of the lattice is zero producing thereby an anisotropic gap in the
single-particle spectrum. It is suggested that this phase occupies the
"pseudogap" region of the phase diagram of the cuprates. The temperature
dependence of the single-particle spectra, the density of states, the specific
heat and the magnetic susceptibility are calculated with rather remarkable
correspondence with the experimental results. The importance of further direct
experimental verification of such a phase in resolving the principal issues in
the theory of the Cuprate phenomena is pointed out. To this end, some
predictions are provided.Comment: 41 pages, 8 figure
- …