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Subhash C Mishra - One of the best experts on this subject based on the ideXlab platform.

  • analysis of non fourier conduction and volumetric radiation in a concentric spherical shell using lattice boltzmann method and finite volume method
    International Journal of Heat and Mass Transfer, 2014
    Co-Authors: Subhash C Mishra, Harsh Sahai
    Abstract:

    Abstract Application of the lattice Boltzmann method (LBM) has been extended to formulate and solve the Energy Equation of a non-Fourier conduction and radiation heat transfer problem in a concentric spherical shell. The enclosed conducting-radiating medium is absorbing, emitting and scattering. The non-Fourier conduction effect is induced by thermally perturbing one of the boundaries and incorporating the finite propagation speed of the thermal wave front in Fourier’s law of heat conduction. The volumetric radiative information needed in the Energy Equation has been computed using the finite volume method (FVM). To establish the accuracy of the LBM approach, with volumetric radiative information obtained from the FVM, the Energy Equation is also solved using the FVM. Effects of extinction coefficient, scattering albedo, conduction–radiation parameter, emissivity, radius ratio and the magnitude of thermal perturbations are studied on transient temperature distributions. Effects of the aforesaid parameters on the steady-state conduction, radiation and total Energy flow rates are also studied. Steady-state LBM and FVM results are compared. In all the cases, the LBM results compare exceedingly well with the FVM results, and LBM has a faster convergence than the FVM.

  • analysis of non fourier conduction and radiation in a cylindrical medium using lattice boltzmann method and finite volume method
    International Journal of Heat and Mass Transfer, 2013
    Co-Authors: Subhash C Mishra, Harsh Sahai
    Abstract:

    Abstract Combined mode heat transfer in a conducting–radiating participating medium bounded by a concentric cylindrical enclosure is studied. The finite propagation speed of heat transfer by conduction is accounted by modifying the Fourier’s law of heat conduction. The Energy Equation is formulated and solved using the lattice Boltzmann method. The finite volume method is used to compute the volumetric radiative information needed in the Energy Equation. Radial distributions of temporal temperature and the steady-state conductive, radiative and total Energy flow rates are analyzed for a wide range of parameters, such as the extinction coefficient, the scattering albedo, the conduction–radiation parameter, the emissivity and the radius ratio. With volumetric radiative information computed using the finite volume method, in all cases, the steady-state temperature distributions from the lattice Boltzmann method are compared with those obtained by solving the Energy Equation using the finite difference method. An excellent comparison is obtained.

  • lattice boltzmann method applied to the analysis of transient conduction radiation problems in a cylindrical medium
    Numerical Heat Transfer Part A-applications, 2009
    Co-Authors: Subhash C Mishra, Man Young Kim, Ranjan Das, M Ajith, Ramagopal Uppaluri
    Abstract:

    The lattice Boltzmann method (LBM) is applied to solve the Energy Equation of a transient conduction-radiation heat transfer problem in a 1-D concentric cylindrical participating medium. The finite-volume method (FVM) is used to obtain the radiative information. To study the effectiveness of the LBM-FVM combination to conduction-radiation problems in cylindrical media, the Energy Equation of the problem is also solved using the finite-difference method (FDM) in which the FVM is used to compute radiative information. The effects of different parameters, such as the conduction-radiation parameter, the scattering albedo, the extinction coefficient, and the radius ratio on temperature distributions in the medium are studied. Results of the present work are benchmarked against those available in the literature. LBM-FVM results are also compared with those obtained by the FDM-FVM combination. In all cases, excellent agreement has been obtained.

  • lattice boltzmann method applied to the solution of Energy Equation of a radiation and non fourier heat conduction problem
    Numerical Heat Transfer Part A-applications, 2008
    Co-Authors: Subhash C Mishra, T Pavan B Kumar, Bittagopal Mondal
    Abstract:

    This article concerns the application of the lattice Boltzmann method (LBM) to solve the Energy Equation of a combined radiation and non-Fourier conduction heat transfer problem. The finite propagation speed of the thermal wave front is accounted by non-Fourier heat conduction Equation. The governing Energy Equation is solved using the LBM. The finite-volume method (FVM) is used to compute the radiative information. The formulation is validated by taking test cases in 1-D planar absorbing, emitting, and scattering medium whose west boundary experiences a sudden rise in temperature, or, with adiabatic boundaries, the medium is subjected to a sudden localized Energy source. Results are analyzed for the various values of parameters like the extinction coefficient, the scattering albedo, the conduction-radiation parameter, etc., on temperature distributions in the medium. Radiation has been found to help in facilitating faster distribution of Energy in the medium. Unlike Fourier conduction, wave fronts have b...

  • solving transient conduction and radiation heat transfer problems using the lattice boltzmann method and the finite volume method
    Journal of Computational Physics, 2007
    Co-Authors: Subhash C Mishra, Hillol K Roy
    Abstract:

    The lattice Boltzmann method (LBM) was used to solve the Energy Equation of a transient conduction-radiation heat transfer problem. The finite volume method (FVM) was used to compute the radiative information. To study the compatibility of the LBM for the Energy Equation and the FVM for the radiative transfer Equation, transient conduction and radiation heat transfer problems in 1-D planar and 2-D rectangular geometries were considered. In order to establish the suitability of the LBM, the Energy Equations of the two problems were also solved using the FVM of the computational fluid dynamics. The FVM used in the radiative heat transfer was employed to compute the radiative information required for the solution of the Energy Equation using the LBM or the FVM (of the CFD). To study the compatibility and suitability of the LBM for the solution of Energy Equation and the FVM for the radiative information, results were analyzed for the effects of various parameters such as the scattering albedo, the conduction-radiation parameter and the boundary emissivity. The results of the LBM-FVM combination were found to be in excellent agreement with the FVM-FVM combination. The number of iterations and CPU times in both the combinations were found comparable.

Alex Hall - One of the best experts on this subject based on the ideXlab platform.

  • constraining the dark Energy Equation of state with double source plane strong lenses
    Monthly Notices of the Royal Astronomical Society, 2012
    Co-Authors: Thomas E Collett, Matthew W Auger, V Belokurov, P J Marshall, Alex Hall
    Abstract:

    We investigate the possibility of constraining the dark Energy Equation of state by measuring the ratio of Einstein radii in a strong gravitational lens system with two source planes. This quantity is independent of the Hubble parameter and directly measures the growth of angular diameter distances as a function of redshift. We investigate the prospects for a single double-source plane system and for a forecast population of systems discovered by re-observing a population of single-source lenses already known from a photometrically selected catalogue such as Cambridge and Sloan survey of wide arcs in the sky or from a spectroscopically selected catalogue such as Sloan Lens ACS survey. We find that constraints comparable to current data sets (σ(w) ∼ 15 per cent) are possible with a handful of double-source plane systems. We also find that the method's degeneracy between ΩM and w is almost orthogonal to that of cosmic microwave background and Baryon Acoustic Oscillations measurements, making this method highly complimentary to current probes.

  • constraining the dark Energy Equation of state with double source plane strong lenses
    arXiv: Cosmology and Nongalactic Astrophysics, 2012
    Co-Authors: Thomas E Collett, Matthew W Auger, V Belokurov, P J Marshall, Alex Hall
    Abstract:

    We investigate the possibility of constraining the dark Energy Equation of state by measuring the ratio of Einstein radii in a strong gravitational lens system with two source planes. This quantity is independent of the Hubble parameter and directly measures the growth of angular diameter distances as a function of redshift. We investigate the prospects for a single double source plane system and for a forecast population of systems discovered by re-observing a population of single source lenses already known from a photometrically selected catalogue such as CASSOWARY or from a spectroscopically selected catalogue such as SLACS. We find that constraints comparable to current data-sets (15% uncertainty on the dark Equation of state at 68%CL) are possible with a handful of double source plane systems. We also find that the method's degeneracy between Omega_M and w is almost orthogonal to that of CMB and BAO measurements, making this method highly complimentary to current probes.

Thomas E Collett - One of the best experts on this subject based on the ideXlab platform.

  • constraining the dark Energy Equation of state with double source plane strong lenses
    Monthly Notices of the Royal Astronomical Society, 2012
    Co-Authors: Thomas E Collett, Matthew W Auger, V Belokurov, P J Marshall, Alex Hall
    Abstract:

    We investigate the possibility of constraining the dark Energy Equation of state by measuring the ratio of Einstein radii in a strong gravitational lens system with two source planes. This quantity is independent of the Hubble parameter and directly measures the growth of angular diameter distances as a function of redshift. We investigate the prospects for a single double-source plane system and for a forecast population of systems discovered by re-observing a population of single-source lenses already known from a photometrically selected catalogue such as Cambridge and Sloan survey of wide arcs in the sky or from a spectroscopically selected catalogue such as Sloan Lens ACS survey. We find that constraints comparable to current data sets (σ(w) ∼ 15 per cent) are possible with a handful of double-source plane systems. We also find that the method's degeneracy between ΩM and w is almost orthogonal to that of cosmic microwave background and Baryon Acoustic Oscillations measurements, making this method highly complimentary to current probes.

  • constraining the dark Energy Equation of state with double source plane strong lenses
    arXiv: Cosmology and Nongalactic Astrophysics, 2012
    Co-Authors: Thomas E Collett, Matthew W Auger, V Belokurov, P J Marshall, Alex Hall
    Abstract:

    We investigate the possibility of constraining the dark Energy Equation of state by measuring the ratio of Einstein radii in a strong gravitational lens system with two source planes. This quantity is independent of the Hubble parameter and directly measures the growth of angular diameter distances as a function of redshift. We investigate the prospects for a single double source plane system and for a forecast population of systems discovered by re-observing a population of single source lenses already known from a photometrically selected catalogue such as CASSOWARY or from a spectroscopically selected catalogue such as SLACS. We find that constraints comparable to current data-sets (15% uncertainty on the dark Equation of state at 68%CL) are possible with a handful of double source plane systems. We also find that the method's degeneracy between Omega_M and w is almost orthogonal to that of CMB and BAO measurements, making this method highly complimentary to current probes.

Marcelo J S De Lemos - One of the best experts on this subject based on the ideXlab platform.

  • laminar heat transfer in a moving porous bed reactor simulated with a macroscopic two Energy Equation model
    International Journal of Heat and Mass Transfer, 2012
    Co-Authors: Ana C Pivem, Marcelo J S De Lemos
    Abstract:

    Abstract This work investigates the influence of physical properties on heat transfer between the solid and fluid phases in a porous reactor, in which both the permeable bed and the working fluid move in the same direction with respect to fixed bounding walls. For simulating laminar flow and heat transfer, a two-Energy Equation model is applied in addition to a mechanical model. Transport Equations are discretized using the control-volume method and the system of algebraic Equations is relaxed via the SIMPLE algorithm. The effects of Reynolds number, solid-to-fluid velocity ratio, permeability, porosity, ratio of solid-to-fluid thermal capacity and ratio of solid-to-fluid thermal conductivity on flow and heat transport are analyzed. The laminar model is validated by means of an analytical solution. Results for concurrent laminar flow indicate that, when the speed of the solid approaches that of the fluid, the strong axial convection of the solid, as well as the reduction of the relative velocity, cause an increase in the axial length needed for thermal equilibrium between phases to occur. Longer thermal developing lengths are also found for higher permeabilities and higher porosities. For higher solid-to-fluid thermal capacities and higher solid-to-fluid thermal conductivity ratios, the temperature of the solid phase shows less axial variation regardless of its velocity in relation to the fluid phase.

  • a correlation for interfacial heat transfer coefficient for turbulent flow over an array of square rods
    Journal of Heat Transfer-transactions of The Asme, 2006
    Co-Authors: Marcelo B Saito, Marcelo J S De Lemos
    Abstract:

    Interfacial heat transfer coefficients in a porous medium modeled as a staggered array of square rods are numerically determined. High and low Reynolds k-e turbulence models are used in conjunction of a two-Energy Equation model, which in chides distinct transport Equations for the fluid and the solid phases. The literature has documented proposals for macroscopic Energy Equation modeling for porous media considering the local thermal equilibrium hypothesis and laminar flow. In addition, two-Energy Equation models have been proposed for conduction and laminar convection in packed beds. With the aim of contributing to new developments, this work treats turbulent heat transport modeling in porous media under the local thermal nonequilibrium assumption. Macroscopic time-average Equations for continuity, momentum, and Energy are presented based on the recently established double decomposition concept (spatial deviations and temporal fluctuations of flow properties). The numerical technique employed for discretizing the governing Equations is the control volume method. Turbulent flow results for the macroscopic heat transfer coefficient, between the fluid and solid phase in a periodic cell, are presented.

  • interfacial heat transfer coefficient for non equilibrium convective transport in porous media
    International Communications in Heat and Mass Transfer, 2005
    Co-Authors: Marcelo B Saito, Marcelo J S De Lemos
    Abstract:

    The literature has documented proposals for macroscopic Energy Equation modeling for porous media considering the local thermal equilibrium hypothesis and laminar flow. In addition, two-Energy Equation models have been proposed for conduction and laminar convection in packed beds. With the aim of contributing to new developments, this work treats turbulent heat transport modeling in porous media under the local thermal non-equilibrium assumption. Macroscopic time-average Equations for continuity, momentum and Energy are presented based on the recently established double decomposition concept (spatial deviations and temporal fluctuations of flow properties). Interfacial heat transfer coefficients are numerically determined for an infinite medium over which the fully developed flow condition prevails. The numerical technique employed for discretizing the governing Equations is the control volume method. Preliminary laminar flow results for the macroscopic heat transfer coefficient, between the fluid and solid phase in a periodic cell, are presented.

A Lankadasu - One of the best experts on this subject based on the ideXlab platform.

  • application of the lattice boltzmann method for solving the Energy Equation of a 2 d transient conduction radiation problem
    International Journal of Heat and Mass Transfer, 2005
    Co-Authors: Subhash C Mishra, A Lankadasu, Kamen N Beronov
    Abstract:

    Abstract A lattice Boltzmann method (LBM) is used to solve the Energy Equation in a test problem involving thermal radiation and to thus investigate the suitability of scalar diffusion LBM for a new class of problems. The problem chosen is transient conductive and radiative heat transfer in a 2-D rectangular enclosure filled with an optically absorbing, emitting and scattering medium. The Energy Equation of the problem is solved alternatively with a previously used finite volume method (FVM) and with the LBM, while the radiative transfer Equation is solved in both cases using the collapsed dimension method. In a parametric study on the effects of the conduction–radiation parameter, extinction coefficient, scattering albedo, and enclosure aspect ratio, FVM and LBM are compared in each case. It is found that, for given level of accuracy, LBM converges in fewer iterations to the steady-state solution, independent of the influence of radiation. On the other hand, the computational cost per iteration is higher for LBM than for the FVM for a simple grid. For coupled radiation–diffusion, the LBM is faster than the FVM because the radiative transfer computation is more time-consuming than that of diffusion.

  • transient conduction radiation heat transfer in participating media using the lattice boltzmann method and the discrete transfer method
    Numerical Heat Transfer Part A-applications, 2005
    Co-Authors: Subhash C Mishra, A Lankadasu
    Abstract:

    ABSTRACT The lattice Boltzmann method (LBM) is used to solve the Energy Equation of a problem involving conduction and radiation heat transfer with and without heat generation. Both steady and transient situations are considered. To demonstrate that the two different kinds of methods can be coupled, the radiative information for the governing Energy Equation is computed using the discrete transfer method and the LBM is used to solve the Energy Equation. For validation purposes, a 1-D planar conducting and radiating medium is considered. Radiatively, the medium is absorbing, emitting, and scattering. Boundaries of the medium are assumed at the specified temperatures. The heat-generation rate is considered uniform and constant throughout the medium. Transient and steady-state medium temperature and heat flux distributions are found for various values of the scattering albedo, emissivity, and conduction-radiation parameter. Results obtained by solving the Energy Equation using the LBM are compared against th...