1,593 research outputs found
POLICY EDUCATION ON NON-TRADITIONAL SUBJECTS: A PROGRAM ON PUBLIC UTILITY REGULATION
Public Economics,
Variational bounds on the energy dissipation rate in body-forced shear flow
A new variational problem for upper bounds on the rate of energy dissipation
in body-forced shear flows is formulated by including a balance parameter in
the derivation from the Navier-Stokes equations. The resulting min-max problem
is investigated computationally, producing new estimates that quantitatively
improve previously obtained rigorous bounds. The results are compared with data
from direct numerical simulations.Comment: 15 pages, 7 figure
Exponentially growing solutions in homogeneous Rayleigh-Benard convection
It is shown that homogeneous Rayleigh-Benard flow, i.e., Rayleigh-Benard
turbulence with periodic boundary conditions in all directions and a volume
forcing of the temperature field by a mean gradient, has a family of exact,
exponentially growing, separable solutions of the full non-linear system of
equations. These solutions are clearly manifest in numerical simulations above
a computable critical value of the Rayleigh number. In our numerical
simulations they are subject to secondary numerical noise and resolution
dependent instabilities that limit their growth to produce statistically steady
turbulent transport.Comment: 4 pages, 3 figures, to be published in Phys. Rev. E - rapid
communication
Variational bound on energy dissipation in turbulent shear flow
We present numerical solutions to the extended Doering-Constantin variational
principle for upper bounds on the energy dissipation rate in plane Couette
flow, bridging the entire range from low to asymptotically high Reynolds
numbers. Our variational bound exhibits structure, namely a pronounced minimum
at intermediate Reynolds numbers, and recovers the Busse bound in the
asymptotic regime. The most notable feature is a bifurcation of the minimizing
wavenumbers, giving rise to simple scaling of the optimized variational
parameters, and of the upper bound, with the Reynolds number.Comment: 4 pages, RevTeX, 5 postscript figures are available as one .tar.gz
file from [email protected]
Variational bound on energy dissipation in plane Couette flow
We present numerical solutions to the extended Doering-Constantin variational
principle for upper bounds on the energy dissipation rate in turbulent plane
Couette flow. Using the compound matrix technique in order to reformulate this
principle's spectral constraint, we derive a system of equations that is
amenable to numerical treatment in the entire range from low to asymptotically
high Reynolds numbers. Our variational bound exhibits a minimum at intermediate
Reynolds numbers, and reproduces the Busse bound in the asymptotic regime. As a
consequence of a bifurcation of the minimizing wavenumbers, there exist two
length scales that determine the optimal upper bound: the effective width of
the variational profile's boundary segments, and the extension of their flat
interior part.Comment: 22 pages, RevTeX, 11 postscript figures are available as one
uuencoded .tar.gz file from [email protected]
THE FEDERAL AGRICULTURE IMPROVEMENT AND REFORM ACT OF 1996: COMMODITY AND CONSERVATION PROGRAMS
The Federal Agriculture Improvement and Reform Act contains major revisions in farm commodity programs. This paper summarizes the major provision of legislation. Because many program implementation rules must be developed, program participants are advised to consult their local office of the USDA Farm Service Agency for final program provisions.Agricultural and Food Policy,
A PREVIEW OF THE 1996 FARM PROGRAM PROVISIONS
The U.S. House of Representatives and Senate have written farm bills that contain major revisions in farm commodity programs. Differences in these bills, House bill HR 2854 and Senate bill S 1541, must now be resolved by a Conference Committee, approved by a final vote of both houses of Congress, and signed by the President. Though differences in the bills do exist, the bills contain many similar provisions that appear likely to be included in the final version of the bill. This paper summarizes the major provisions of these bills and identifies areas where differences must be resolved by the Conference Committee.Agricultural and Food Policy,
On the universality of a class of annihilation-coagulation models
A class of -dimensional reaction-diffusion models interpolating
continuously between the diffusion-coagulation and the diffusion-annihilation
models is introduced. Exact relations among the observables of different models
are established. For the one-dimensional case, it is shown how correlations in
the initial state can lead to non-universal amplitudes for time-dependent
particles density.Comment: 18 pages with no figures. Latex file using REVTE
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