Swarup K. Mahapatra

Interaction of surface radiation and variable property natural convection in a differentially heated square cavity – a finite element analysis

A finite element solution on the interaction of surface radiation and variable property laminar natural convection is presented. Finite element formulation of the governing equations, associated with variable property natural convection, and incorporation of the radiative boundary conditions has been extensively discussed. The study also aims to highlight the limiting value of the terminal temperature difference (TTD), below which the natural convection heat transfer becomes the sole heat transfer mode, i.e. the effect of surface radiation can be neglected. The effects of variations of emissivity and TTD are also presented.

Thermosolutal Convection in a Rectangular Concentric Annulus: A Comprehensive Study

This investigation presents numerical treatment of governing equations pertaining to thermosolutal flow within an annulus and an application of a model describing the important physical phenomenon as found in muffle furnace. The inner side of the annulus is exposed to high temperature and high solute concentration while the outer side of the annulus is maintained at low temperature and low solute concentration. Darcy-Brinkman-Forchheimer model is used to study the flow, heat and solute transfer in a non-Darcian saturated porous media. The solution is obtained upon application of control volume integration. Modified MAC method is used for the numerical solution of governing equations. Gradient dependent consistent hybrid upwind scheme of second order (GDCHUSSO) is used for discretization of the convective terms. The parameters such as Rayleigh-Darcy number, Darcy number, buoyancy ratio and width ratio, that govern the flow phenomenon have been identified and their effects are critically examined. The fluid flow pattern in the annular space and the associated heat and mass transfer are conceptualized from the obtained isoconcentration, isotherm and flowline contour maps.

Mixed Convection Inside a Differentially Heated Enclosure and its Interaction with Radiation—An Exhaustive Study

This study addresses the numerical modeling aspects of transport phenomena in steady, two-dimensional, laminar flow accompanied by heat transfer in a differentially heated cavity with moving walls in presence of radiatively absorbing, emitting, and scattering gray medium. The discrete ordinate method has been used in modeling the radiative transport equation and the finite difference method based on a finite volume approach is used as the discretization technique. Two cases of mixed convection arising out of vertical isothermal wall movement and horizontal adiabatic wall movement and their interaction with radiation have been critically examined. Both buoyancy-aided and buoyancy-opposed mixed convection have been investigated, but buoyancy-opposed mixed convection interacting with radiation has been given emphasis in the present work due to some exciting revelations. The effects of Richardsons number (from 0.1 to 10), radiation-conduction parameter, single scattering albedo, and optical thickness on fluid flow and energy transfer have been studied. An exhaustive comparison between influences of radiation on mixed convection arising due to vertical isothermal wall and horizontal adiabatic wall movement has been made.

Coupled magneto-buoyant convection and radiation in an inclined enclosure

Purpose – The current study aims to address the interaction between participating media radiation with thermo-gravitational convection of an electrically conducting fluid enclosed within a tilted enclosure under an externally imposed time-independent uniform magnetic field. Design/methodology/approach – The differentially heated boundaries of the tilted enclosure are considered to be diffuse, gray and the enclosed fluid is assumed to be absorbing, emitting and isotropically scattering. The Navier-Stokes equations, meant for magneto convection are solved using modified MAC method. Gradient dependent consistent hybrid upwind scheme of second order is used for discretization of the convective terms. Discrete ordinate method, with S8 approximation, is used to model radiative transport equation in the presence of radiatively active medium. Findings – Effect of uniform magnetic field with different magnitudes and orientations of cavity has been numerically simulated. The effect of participating media radiation ...

Development of a Novel Improved Differential Approximation (NIDA) for Analysis of Combined Conduction-Radiation Heat Transfer (CCR) in a Two-Dimensional Enclosure with Participating Medium: An Experimental Validation

This numerical investigation addresses the applicability and adaptability of the novel improved differential approximation (NIDA) for combined conduction-radiation heat transfer (CCR) in a two-dimensional enclosure with radiatively participating gray medium. The NIDA is developed by blending the spherical harmonic method with the ray emission model and the zonal method. The first-order spherical harmonics, i.e., P1 approximation results, are improved and validated with a similar type of analysis as in Kims discrete ordinates method (DOM), the hybrid method, and other CCR models. The application and robustness of the NIDA model for a wide range of radiative properties of the medium has been examined, and results are presented for benchmarking the solution. Furthermore, the favorable agreement of numerically obtained isotherms with interferograms captured by a Mach-Zehnder interferometer demonstrates the realistic nature of the NIDA.

A Numerical Investigation of Surface Radiation Interaction With Magneto-Convection of an Electrically Conducting Fluid Imposed With a Transverse Magnetic Field

In the present study, analysis has been performed to investigate the surface radiation effect on hydro-magnetic buoyant convection of an electrically conducting fluid in a differentially heated cavity. The fluid is enclosed within a gray chamber and imposed with a uniform magnetic field orthogonal to the vertical cross-sectional plane of the chamber. Numerical solution is done by control volume integration. A modified Marker and Cell method is used for the solution of the governing equation for flow transport. A gradient-dependent consistent hybrid upwind scheme of second order is used for discretization of the convective terms. The transport equation for surface radiation is solved using a net radiation method. Cross-string method is used to compute the view factor. Comprehensive studies on the controlling parameters that affect the flow and heat transfer characteristics are delineated. The results are presented in tabular and graphical form. The heat transfer and flow characteristics are depicted in form of isotherms and streamlines revealing the concealed physics of a complex phenomenon.

Divergence of Radiative Heat Flux in Ultra-Short Time Scale in Axisymmetric Geometry With its Implications

An axisymmetric transient radiative heat transfer model is developed taking into account the new formulation of divergence of radiative heat flux in ultrashort time scale. In order to predict the medium temperature, divergence of radiative heat flux is coupled with the energy equation. The conventional quasi steady divergence of radiative heat flux is modified taking into account the transient effect of photon transport. An axisymmetric domain is taken as a physical model in the present analysis. A critical examination revealed that even for pure scattering medium, the diveregence of flux is a non-zero quantity due to the inclusion of the new term called as propagation term in the formulation of the divergence of radiative heat flux in ultrashort time scale. A two-dimensional scheme is proposed to solve the radiative transfer equation (RTE) in an axisymmeric cylindrical domain. The step spatial scheme is used for discretizing the spatial term in the RTE. The medium is assumed to be absorbing, emitting and isotropically scattering. The walls are assumed as diffuse and gray. It is observed that the conventional quasi-steady divergence of radiative heat flux underpredicts the temperature of the medium in the time scale of the order of characteristic time scale of photon where transient radiation effect is predominant.© 2013 ASME

Coupled phenomenon of opposing mixed convection and radiation in presence of participating medium inside eccentric horizontal cylindrical annulus

In the present investigation, the coupled phenomenon of opposing mixed convection and radiation within differentially-heated eccentric horizontal cylindrical annulus has been numerically simulated. The radiation transfer contributed from the participating medium is obtained by solving the non-linear integro-differential radiative transfer equation using the discrete ordinate method. The participating grey medium is considered to be emitting, absorbing, and isotropically scattering. The walls of the annulus are considered to be opaque, diffuse, and grey. From the present investigation, it is found that substantial changes occur in the isotherms as well as the flow patterns, when the Richardson number is allowed to vary in the range of 0.01–1. The eccentricity of the inner cylinder has been varied adequately to illustrate the effect of same in a focused manner. The influence of radiative parameters on the interaction phenomenon has been delineated through the isotherm and streamline patterns.