scholarly journals Decay of Temperature Fluctuations in Homogeneous Turbulence before the Final Period for the Case of Multi-Point and Multi-Time in a Rotating System

1970 ◽  
Vol 41 (3) ◽  
pp. 147-158
Author(s):  
MS Alam Sarker ◽  
MAK Azad
Keyword(s):  
Energy Spectrum ◽  
Fourier Transforms ◽  
Temperature Fluctuations ◽  
Homogeneous Turbulence ◽  
Correlation Equations ◽  
Spectral Form ◽  
Third Order ◽  
Rotating System ◽  
Wave Numbers ◽  
Point Correlation

Using Deissler’s approach the decay of temperature fluctuations in homogeneous turbulence before the final period for the case of multi-point and multi-time in a rotating system in presence of dust particle is studied and have considered correlation between fluctuating quantities at two and three point. Two and three point correlation equations in a rotating system is obtained and the set of equations is made to determinate by neglecting the quadruple correlations in comparison to the second and third order correlations. The correlations are converted to spectral form by taking their Fourier transforms. Finally integrating the energy spectrum over all wave numbers, the energy decay law of temperature fluctuations in homogeneous turbulent before the final period for the case of multi-point and multi-time in a rotating system is obtained. Bangladesh J. Sci. Ind. Res. 41(3-4), 147-158 2006

scholarly journals Decay of Temperature Fluctuations in MHD Turbulence before the Final Period in a Rotating System

1970 ◽  
Vol 44 (4) ◽  
pp. 407-414
Author(s):  
M Abul Kalam Azad ◽  
MS Alam Sarker
Keyword(s):  
Energy Spectrum ◽  
Fourier Transforms ◽  
Temperature Fluctuations ◽  
Correlation Equations ◽  
Mhd Turbulence ◽  
Third Order ◽  
Rotating System ◽  
Wave Numbers ◽  
System Temperature ◽  
Point Correlation

Using Deissler's approach the Decay of temperature fluctuations in MHD turbulence before the final period in a rotating system is studied and have considered correlations between fluctuating quantities at two and three point. In this case two and three-point correlation equations in a rotating system is obtained and the set of equations is made to determinate by neglecting the quadruple correlations in comparison to the second and third order correlations. The correlation equations are converted to special form by taking their Fourier-transforms. Finally integrating the energy spectrum over all wave numbers the energy decay law of temperature fluctuations in MHD turbulence before the final period in a rotating system is obtained. Key words: Deissler's method; MHD turbulence; Rotating system; Temperature fluctuation. DOI: 10.3329/bjsir.v44i4.4604 Bangladesh J. Sci. Ind. Res. 44(4), 407-414, 2009

scholarly journals Decay of Dusty Fluid MHD Turbulence for Four-point Correlation in a Rotating System

2012 ◽  
Vol 5 (1) ◽  
pp. 77-90
Author(s):  
M. A. Bkar PK ◽  
M. A. K. Azad ◽  
M. S. A. Sarker
Keyword(s):  
Fourier Transforms ◽  
Correlation Equations ◽  
Spectral Form ◽  
Mhd Turbulence ◽  
Rotating System ◽  
Dusty Fluid ◽  
The Third ◽  
Wave Numbers ◽  
Point Correlation ◽  
Correlation System

In this paper we have considered the dusty fluid MHD turbulence in a rotating system at four-point correlation. Here three and four-point correlations between fluctuating quantities have been considered and the quintuple correlations are neglected in comparison to the third and fourth order correlations. For the convention of calculation, the correlation equations are converted to the spectral form by taking their Fourier transforms. Finally, integrating the energy spectrum over all wave numbers, the energy decay of dusty fluid MHD turbulence in a rotating system for four-point correlation system is obtained. © 2013 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved.doi: http://dx.doi.org/10.3329/jsr.v5i1.9996          J. Sci. Res. 5 (1), 77-90 (2013)

scholarly journals Decay of Temperature Fluctuations in MHD Turbulent flow in presence of dust particles before the final period

1970 ◽  
Vol 32 (1) ◽  
pp. 61-70
Author(s):  
ML Rahman
Keyword(s):  
Turbulent Flow ◽  
Fourth Order ◽  
Temperature Fluctuation ◽  
Temperature Fluctuations ◽  
Dust Particles ◽  
Correlation Equations ◽  
Mhd Turbulence ◽  
Third Order ◽  
Point Correlation ◽  
Academy Of Sciences

This paper reports the decay of temperature fluctuation in homogeneous MHD turbulence in the presence of dust particles before the final period. We have considered the two and three point correlation equations and solved them after neglecting the fourth order correlations in comparison with the second and third order correlations. Finally, the energy decay law for temperature fluctuation of MHD turbulence in the presence of dust particles at times before the final period is obtained. doi: 10.3329/jbas.v32i1.2443 Journal of Bangladesh Academy of Sciences, Vol. 32, No. 1, 61-70, 2008

Implicit Large Eddy Simulation of Two-Dimensional Homogeneous Turbulence Using Weighted Compact Nonlinear Scheme

2009 ◽  
Vol 131 (6) ◽  
Author(s):  
Keiichi Ishiko ◽  
Naofumi Ohnishi ◽  
Kazuyuki Ueno ◽  
Keisuke Sawada
Keyword(s):  
Energy Spectrum ◽  
Inertial Range ◽  
Homogeneous Turbulence ◽  
Two Dimensional ◽  
Third Order ◽  
The Third ◽  
Eddy Simulation ◽  
Numerical Viscosity ◽  
Large Eddy ◽  
Implicit Large Eddy Simulation

For the aim of computing compressible turbulent flowfield involving shock waves, an implicit large eddy simulation (LES) code has been developed based on the idea of monotonically integrated LES. We employ the weighted compact nonlinear scheme (WCNS) not only for capturing possible shock waves but also for attaining highly accurate resolution required for implicit LES. In order to show that WCNS is a proper choice for implicit LES, a two-dimensional homogeneous turbulence is first obtained by solving the Navier–Stokes equations for incompressible flow. We compare the inertial range in the computed energy spectrum with that obtained by the direct numerical simulation (DNS) and also those given by the different LES approaches. We then obtain the same homogeneous turbulence by solving the equations for compressible flow. It is shown that the present implicit LES can reproduce the inertial range in the energy spectrum given by DNS fairly well. A truncation of energy spectrum occurs naturally at high wavenumber limit indicating that dissipative effect is included properly in the present approach. A linear stability analysis for WCNS indicates that the third order interpolation determined in the upwind stencil introduces a large amount of numerical viscosity to stabilize the scheme, but the same interpolation makes the scheme weakly unstable for waves satisfying kΔx≈1. This weak instability results in a slight increase in the energy spectrum at high wavenumber limit. In the computed result of homogeneous turbulence, a fair correlation is shown to exist between the locations where the magnitude of ∇×ω becomes large and where the weighted combination of the third order interpolations in WCNS deviates from the optimum ratio to increase the amount of numerical viscosity. Therefore, the numerical viscosity involved in WCNS becomes large only at the locations where the subgrid-scale viscosity can arise in ordinary LES. This suggests the reason why the present implicit LES code using WCNS can resolve turbulent flowfield reasonably well.

scholarly journals First Order Reactant in Magneto-Hydrodynamic Turbulence before the Final Period of Decay in Presence of Dust Particle

1970 ◽  
Vol 45 (1) ◽  
pp. 39-46
Author(s):  
MAK Azad ◽  
MA Aziz ◽  
MS Alam Sarker
Keyword(s):  
Dust Particle ◽  
Fourier Transforms ◽  
Magnetic Energy ◽  
Correlation Equations ◽  
Mhd Turbulence ◽  
First Order ◽  
Particle Decay ◽  
Order Chemical Reaction ◽  
Point Correlation ◽  
First Order Chemical Reaction

Following Deissler's theory, the decay for the concentration fluctuation of a dilute contaminant undergoing a first order chemical reaction in MHD turbulence at times before the final period in presence of dust particle is studied and have considered correlations between fluctuating quantities at two and three point. Two and three point correlation equations are obtained and the set of equations is made to determinate by neglecting the quadruple correlations in comparison to the second and third order correlations. The correlation equations are converted to spectral form by taking their Fourier transforms. Finally we obtained the Decay law of magnetic energy for the concentration fluctuations before the final period in presence of dust particle by integrating the energy spectrum over all wave numbers. Keywords: MHD Turbulence; First order reactant; Dust particle; Decay before the final period DOI: 10.3329/bjsir.v45i1.5182 Bangladesh J. Sci. Ind. Res. 45(1), 39-46, 2010

scholarly journals Электронная структура и спектры оптического поглощения золотых фуллеренов Au-=SUB=-16-=/SUB=- и Au-=SUB=-20-=/SUB=-

2019 ◽  
Vol 61 (6) ◽  
pp. 1204
Author(s):  
Г.И. Миронов
Keyword(s):  
Optical Properties ◽  
Energy Spectrum ◽  
Optical Absorption ◽  
Near Infrared ◽  
Fourier Transforms ◽  
Green Functions ◽  
Optical Absorption Spectra ◽  
New Class ◽  
Infrared Spectral ◽  
Neighboring Site

AbstractThe electronic and optical properties of gold fullerenes are studied in the framework of the Hubbard model. The expressions of the Fourier transforms of anticommutator Green functions have been obtained for gold fullerenes Au_16 and Au_20, the poles of which determine the energy spectrum of the system under consideration. The calculations are performed for the thermodynamic means that characterize jumps of electrons from a nanosystem site to a neighboring site, the correlation functions demonstrating the possibility of existing two d electrons with oppositely oriented spin projections on the same site of the fullerenes consisting of gold atoms. The optical absorption spectra are presented. The optical absorption peaks of ions $${\text{Au}}_{{20}}^{ - }$$ and $${\text{Au}}_{{16}}^{ - }$$ correspond to a near-infrared spectral region, where the light absorption by blood or a soft tissue is vanishingly small; thus, these ions can be used as a new class of contrast improvements and phototherapeutic means for diagnostics and treatment of cancer.

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