3,513 research outputs found
Application of a two-dimensional parabolic computer program to prediction of turbulent reacting flows
The capabilities of a computer program are explored, and computed results are compared with data. The comparisons are restricted to two-dimensional flows. Subsonic and supersonic flows, ducted and nonducted, reacting and nonreacting, are considered. An evaluation of models used for turbulence and chemical reaction was included. Constants in the dissipation rate of turbulent kinetic energy, turbulence model, which produces mixing in good agreement with data, are the same for all calculations. Experimental data are reported for coaxial injection at matched pressure (1 atm or 101.3 kPa) of a cold, Mach 2, hydrogen jet into a hot, Mach 2, vitiated airstream. Profiles of pitot pressure and gas composition obtained from water cooled probes are reported and compared with theoretical results
Simulation of 3-D viscous flow within a multi-stage turbine
This work outlines a procedure for simulating the flow field within multistage turbomachinery which includes the effects of unsteadiness, compressibility, and viscosity. The associated modeling equations are the average passage equation system which governs the time-averaged flow field within a typical passage of a blade row embedded within a multistage configuration. The results from a simulation of a low aspect ratio stage and a one-half turbine will be presented and compared with experimental measurements. It will be shown that the secondary flow field generated by the rotor causes the aerodynamic performance of the downstream vane to be significantly different from that of an isolated blade row
Average-passage flow model development
A 3-D model was developed for simulating multistage turbomachinery flows using supercomputers. This average passage flow model described the time averaged flow field within a typical passage of a bladed wheel within a multistage configuration. To date, a number of inviscid simulations were executed to assess the resolution capabilities of the model. Recently, the viscous terms associated with the average passage model were incorporated into the inviscid computer code along with an algebraic turbulence model. A simulation of a stage-and-one-half, low speed turbine was executed. The results of this simulation, including a comparison with experimental data, is discussed
A study of the toxic principle in red clover
A report on Department of Agricultural Chemistry research project 247, Forage Poisoning--P. [2].Digitized 2007 AES.Includes bibliographical references (page 12)
Variational ground states of 2D antiferromagnets in the valence bond basis
We study a variational wave function for the ground state of the
two-dimensional S=1/2 Heisenberg antiferromagnet in the valence bond basis. The
expansion coefficients are products of amplitudes h(x,y) for valence bonds
connecting spins separated by (x,y) lattice spacings. In contrast to previous
studies, in which a functional form for h(x,y) was assumed, we here optimize
all the amplitudes for lattices with up to 32*32 spins. We use two different
schemes for optimizing the amplitudes; a Newton/conjugate-gradient method and a
stochastic method which requires only the signs of the first derivatives of the
energy. The latter method performs significantly better. The energy for large
systems deviates by only approx. 0.06% from its exact value (calculated using
unbiased quantum Monte Carlo simulations). The spin correlations are also well
reproduced, falling approx. 2% below the exact ones at long distances. The
amplitudes h(r) for valence bonds of long length r decay as 1/r^3. We also
discuss some results for small frustrated lattices.Comment: v2: 8 pages, 5 figures, significantly expanded, new optimization
method, improved result
A water-vapor electrolysis cell with phosphoric acid electrolyte
Feasibility of phosphoric acid water vapor electrolysis cell for spacecraft cabin air conditioning syste
Book Reviews
Book reviews by Waldo Beach, James J. Harrington, Rocco L. Puntureri, George P. McAndrews, and William J. Gerardo
A reliable Pade analytical continuation method based on a high accuracy symbolic computation algorithm
We critique a Pade analytic continuation method whereby a rational polynomial
function is fit to a set of input points by means of a single matrix inversion.
This procedure is accomplished to an extremely high accuracy using a novel
symbolic computation algorithm. As an example of this method in action we apply
it to the problem of determining the spectral function of a one-particle
thermal Green's function known only at a finite number of Matsubara frequencies
with two example self energies drawn from the T-matrix theory of the Hubbard
model. We present a systematic analysis of the effects of error in the input
points on the analytic continuation, and this leads us to propose a procedure
to test quantitatively the reliability of the resulting continuation, thus
eliminating the black magic label frequently attached to this procedure.Comment: 11 pages, 8 eps figs, revtex format; revised version includes
reference to anonymous ftp site containing example codes (MapleVr5.1
worksheets) displaying the implementation of the algorithm, including the
padematinv.m library packag
Why mainstream parties change policy on migration: A UK case study - The Conservative Party, immigration and asylum, 1960-2010
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