11,285 research outputs found
Field theoretic calculation of scalar turbulence
The cascade rate of passive scalar and Bachelor's constant in scalar
turbulence are calculated using the flux formula. This calculation is done to
first order in perturbation series. Batchelor's constant in three dimension is
found to be approximately 1.25. In higher dimension, the constant increases as
.Comment: RevTex4, publ. in Int. J. Mod. Phy. B, v.15, p.3419, 200
Incompressible Turbulence as Nonlocal Field Theory
It is well known that incompressible turbulence is nonlocal in real space
because sound speed is infinite in incompressible fluids. The equation in
Fourier space indicates that it is nonlocal in Fourier space as well. Contrast
this with Burgers equation which is local in real space. Note that the sound
speed in Burgers equation is zero. In our presentation we will contrast these
two equations using nonlocal field theory. Energy spectrum and renormalized
parameters will be discussed.Comment: 7 pages; Talk presented in Conference on "Perspectives in Nonlinear
Dynamics (PNLD 2004)" held in Chennai, 200
Energy fluxes in helical magnetohydrodynamics and dynamo action
Renormalized viscosity, renormalized resistivity, and various energy fluxes
are calculated for helical magnetohydrodynamics using perturbative field
theory. The calculation is to first-order in perturbation. Kinetic and magnetic
helicities do not affect the renormalized parameters, but they induce an
inverse cascade of magnetic energy. The sources for the the large-scale
magnetic field have been shown to be (1) energy flux from large-scale velocity
field to large-scale magnetic field arising due to nonhelical interactions, and
(2) inverse energy flux of magnetic energy caused by helical interactions.
Based on our flux results, a premitive model for galactic dynamo has been
constructed. Our calculations yields dynamo time-scale for a typical galaxy to
be of the order of years. Our field-theoretic calculations also reveal
that the flux of magnetic helicity is backward, consistent with the earlier
observations based on absolute equilibrium theory.Comment: REVTEX4; A factor of 2 corrected in helicit
Strategies for Improving Indian Railways’ Market Share of Port Based Coal Traffic: A Diagnostic Study
India is a vast country. After its independence in 1947, it steadily lost its position in international trade. With the beginning of economic liberalization in 1991, it has taken new initiatives in integrating itself with the world economy. Import restrictions have been removed for many commodities. One of the major impacts of liberalization has been on infrastructure: railways, roadways, ports and airports. Significant changes have also taken place in the composition of imported and exported commodities. Due to these changes, new challenges are being faced on the infrastructure front. One of the challenges is to rectify the mismatch of available infrastructure at ports where a modal change of commodities that are either imported or exported takes place. This paper examines such issues with a specific focus on improving infrastructure required for integration of railways and ports. This is achieved by focusing on coal which is a commodity that (i) brings significant revenues to Indian Railways, and (ii) is witnessing increasing imports. In this diagnostic study, we discuss the problems faced by Indian Railways and identify ways to increase its market share of coal movement between ports and the hinterland.
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