S. Ramadhyani

Bio: S. Ramadhyani is an academic researcher from Purdue University. The author has contributed to research in topics: Natural convection & Nusselt number. The author has an hindex of 6, co-authored 6 publications receiving 679 citations.

Natural convection flow and heat transfer between a fluid layer and a porous layer inside a rectangular enclosure

Abstract: Etude numerique et experimentale. Modelisation de l'ecoulement dans la couche poreuse a l'aide de l'equation de Darcy etendue par Brinkman et Forchheimer. Verification experimentale sur des ecoulements d'eau et de glycerine dans un milieu constitue de billes de verre

A numerical study of non-darcian natural convection in a vertical enclosure filled with a porous medium

Abstract: A numerical study of non-Darcian natural convection in a vertical enclosure filled with a porous medium is performed. The flow is modeled using the Brinkman-Forchheimer-extended Darcy equations. The governing equations are solved with the SIMPLER algorithm and good agreement with previously reported numerical and experimental results is found. An order of magnitude analysis and the numerical results demonstrate the importance of non-Darcian effects. For high Darcy numbers (Da > 10−4), both extensions are of the same order of magnitude and must be used simultaneously. In addition, Forch-heimer's extension must be included for Pr ≤ 1.0 and all Darcy numbers. Finally, Nusselt number correlations are presented for three different ranges of the Darcy number covering wide ranges of the governing parameters.

Natural convection in vertical enclosures containing simultaneously fluid and porous layers

Abstract: A numerical and experimental study is reported of natural convection in a vertical rectangular fluid enclosure that is partially filled with a fluid-saturated porous medium. Velocities, stresses, temperatures, and heat fluxes are assumed to be continuous across the fluid/porous-medium interface, and the conservation equations for the fluid and the porous regions are combined into a single set of equations for numerical solution. Thermocouples as well as a Mach-Zehnder interferometer are used to measure temperature distributions and infer fluid flow patterns within the fluid and the porous medium. For various test cells, porous-layer configurations and fluid-solid combinations, the model predictions show excellent agreement with the experimental measurements. It is found that the intensity of natural convection is always much stronger in the fluid regions, while the amount of fluid penetrating into the porous medium increases with increasing Darcy and Rayleigh numbers. The degree of penetration of fluid into the porous medium depends strongly on the porous-layer geometry and is less for a horizontal porous layer occupying the lower half of the test cell. If penetration takes place, the flow patterns in the fluid regions are significantly altered and the streamlines show cusps at the fluid/porous-medium interfaces. For a high effective-thermal-conductivity porous medium, natural convection in the medium is suppressed, while the isotherms bend sharply at the fluid/porous-medium interface.

Combined Buoyancy- and Thermocapillary-Driven Convection in Open Square Cavities

Abstract: The characteristics of convective flow in a square cavity driven by simultaneous buoyancy and thermocapillary effects have been studied numerically. Results for two sets of thermal boundary conditions suggest that surface tension effects can significantly alter buoyancy-induced flow. The resulting alteration in the flow field can enhance or reduce heat transfer rates across the cavity.

Laminar Natural Convection in a Discretely Heated Cavity: I—Assessment of Three-Dimensional Effects

Abstract: Two and three-dimensional calculations have been performed for laminar natural convection induced by a 3 X 3 array of discrete heat sources flush-mounted to one vertical wall of a rectangular cavity whose opposite wall was isothermally cooled. Edge effects predicted by the three-dimensional model yielded local and average Nusselt numbers that exceeded those obtained from the two-dimensional model, as well as average surface temperatures that were smaller than the two-dimensional predictions. For heater aspect ratios A htr ≤ 3, average Nusselt numbers increased with decreasing A htr . However, for A htr ≥ 3, the two and three-dimensional predictions were within 5 percent of each other and results were approximately independent of A htr .

On the ability of a Darcy-scale model to capture wormhole formation during the dissolution of a porous medium

Abstract: Dissolution of a porous medium creates, under certain conditions, some highly conductive channels called wormholes. The mechanism of propagation is an unstable phenomenon depending on the microscopic properties at the pore scale and is controlled by the injection rate. The aim of this work is to test the ability of a Darcy-scale model to describe the different dissolution regimes and to characterize the influence of the flow parameters on the wormhole development. The numerical approach is validated by model experiments reflecting dissolution processes occurring during acid injection in limestone. Flow and transport macroscopic equations are written under the assumption of local mass non-equilibrium. The coupled system of equations is solved numerically in two dimensions using a finite volume method. Results are discussed in terms of wormhole propagation rate and pore volume injected.

A lattice boltzmann model for convection heat transfer in porous media

Abstract: A lattice Boltzmann model for convection heat transfer in porous media is proposed. In this model, a new distribution function is introduced to simulate the temperature field in addition to the density distribution function for the velocity field. The macroscopic equations for convection heat transfer in porous media are recovered from the model through the Chapman-Enskog procedure. The model is validated by several benchmark problems, and it is found that the numerical results are in good agreement with the well-documented results in the literature.