Papers by Prof. T Sundararajan Sundararajan
Numerical Prediction of Molten Metal Jet Dynamics, Fragmentation and Solidification in a Coolant Pool
2010 14th International Heat Transfer Conference, Volume 7, 2010
The hydrodynamics of molten metal jet in a coolant pool is characterized by the presence of compl... more The hydrodynamics of molten metal jet in a coolant pool is characterized by the presence of complex and diverse fluid structures whose formation is facilitated by various modes of instabilities acting on the fluid-fluid interface and the bulk material. The large spectrum of scales involved in these processes and the related non-linearities cloud a clear understanding of the associated physical phenomena. In order to overcome these difficulties, a numerical model has been developed in the current work, which aims to simulate the hydrodynamics, fragmentation and solidification of a molten metal jet in the coolant pool. The work uses an axisymmetric flow solver with the Volume of Fluid (VOF) interface tracking model to evaluate the macro features of the molten metal jet dynamics and to predict the evolution of interfacial instabilities. At the same time, the phenomena at the micro scale is predicted by a Lagrangian particle tracking model that is used to capture the dynamics and the he...
Numerical Simulation of Flow of Nanofluids in Microchannel
Pramana, 2005
Increase in the specific surface area as well as Brownian motion are supposed to be the most sign... more Increase in the specific surface area as well as Brownian motion are supposed to be the most significant reasons for the anomalous enhancement in thermal conductivity of nanofluids. This work presents a semi-empirical approach for the same by emphasizing the above two effects through micro-convection. A new way of modeling thermal conductivity of nanofluids has been explored which is found to agree excellently with a wide range of experimental data obtained by the present authors as well as the data published in literature.
Numerical Investigation of Evaporation in the Developing Region of Laminar Falling Film Flow Under Constant Wall Heat Flux Conditions
Numerical Heat Transfer, Part A: Applications, 2010
A finite-volume-based incompressible flow algorithm on Cartesian grid is presented for the simula... more A finite-volume-based incompressible flow algorithm on Cartesian grid is presented for the simulation of evaporation phenomena in a falling liquid film under low wall superheat con-ditions. The model employs the PLICVOF method to capture the free surface evolution, and the continuum ...
Nuclear Engineering and Design, 2011
Sodium leak collection tray (LCT) is an efficient passive device used for the extinguishment of l... more Sodium leak collection tray (LCT) is an efficient passive device used for the extinguishment of liquid sodium fire in case of an accidental leakage from the secondary circuit of a fast breeder reactor. The LCT essentially isolates the leaking sodium into closed containers where the resulting fire is extinguished due to limited availability of oxygen. The current work aims to highlight the combustion extinguishment characteristics of LCT through a lumped formulation by conserving the mass and energy of liquid sodium and constituent gases in various parts of the LCT. Here, the complex hydrodynamics of liquid sodium is emulated through a semi-analytical draining/sloshing model and its burning rates are predicted through a three-dimensional open pool combustion model for the tray region and a closed pool combustion model for the holdup vessel. These simulations evaluate the burning rates at discrete levels of liquid sodium which are subsequently interpolated to establish correlations involving instantaneous liquid levels and oxygen concentration. Using the correlations obtained from the draining and combustion models, the overall lumped formulation directly predicts the un-burnt sodium recoverable after the extinguishment of fire in the LCT. The predicted results of this model compare well with the available experimental data.
Nuclear Engineering and Design, 2005
Fast breeder nuclear reactors used for power generation, have fuel subassemblies in the form of r... more Fast breeder nuclear reactors used for power generation, have fuel subassemblies in the form of rod bundles enclosed inside tall hexagonal cavities. Each subassembly can be considered as a porous medium with internal heat generation. A three-dimensional analysis is carried out here to estimate the heat transfer due to natural convection, in such an anisotropic, partially heat generating porous medium, which corresponds to the typical case of blocked flow in a fuel subassembly inside the reactor core. Using the finite volume technique, the temperatures at various locations inside hexagonal cavity are obtained. The simulations by the three-dimensional code developed are compared with the results of experiments [
Development of a mathematical model for multihearth roasters
Metallurgical Transactions B, 1989
A simultaneous heat and mass transfer model has been developed for the multiheart roasters, consi... more A simultaneous heat and mass transfer model has been developed for the multiheart roasters, considering dead roasting of chalcopyrite as a typical roasting reaction. Various mass and energy balances have been worked out during the development of this model yielding coupled nonlinear partial differential equations with highly complex boundary conditions. These equations have been solved numerically using a line-by-line finite
Journal of Nanoparticle Research, 2009
One of the reasons for the controversy on the thermal conductivity enhancement of nanofluids is t... more One of the reasons for the controversy on the thermal conductivity enhancement of nanofluids is the lack of extensive data over a wide range of parameters. In the present study, a comprehensive experimental dataset is obtained for thermal conductivity of nanofluids with variation in nanoparticle material, base liquid, particle size, particle volume fraction and suspension temperature. Transient hot wire (THW) equipment as well as Temperature Oscillation equipment are developed for the measurement of thermal conductivity of liquids. The measurements show that, in general, thermal conductivity values of all the nanofluids are higher than that of the equivalent macro-particle suspensions. Metallic nanofluids are found to give higher enhancements than that of oxide nanofluids. Particle size is found to have a tremendous impact on the thermal conductivity of nanofluids with enhancement in the thermal conductivity increasing almost inversely with reduction in the particle size. Increase in temperature significantly increases the thermal conductivity of a nanofluid. It is also observed that the thermal conductivity of nanoparticle suspensions is relatively higher at lower volume fractions, thereby giving a non-linear dependence on the particle volume fraction.
A Quadratic Spline based Interface (QUASI) reconstruction algorithm for accurate tracking of two-phase flows
Journal of Computational Physics, 2009
A new Quadratic Spline based Interface (QUASI) reconstruction algorithm is presented which provid... more A new Quadratic Spline based Interface (QUASI) reconstruction algorithm is presented which provides an accurate and continuous representation of the interface in a multiphase domain and facilitates the direct estimation of local interfacial curvature. The fluid interface in each ...
International Journal of Heat and Mass Transfer, 1992
A theoretical model for heat transfer and fluid flow during alloy solidification is presented. A ... more A theoretical model for heat transfer and fluid flow during alloy solidification is presented. A detailed accounting has been made for the property variations in the dendritic phase-change region. A generalized porous medium approach has been adopted, with the variation of permeability being anisotropic. The effects of anisotropy are observed to be significant if the extent of the mushy zone is large or if the Rayleigh number is high.
International Journal of Heat and Mass Transfer, 1999
The natural convective ~ow and associated heat transfer in a ~uid saturated porous medium have be... more The natural convective ~ow and associated heat transfer in a ~uid saturated porous medium have been investigated using the generalised porous medium approach[ Many new features have been predicted with the convective heat transfer boundary condition[ A detailed parametric study reveals that multicellular ~ow patterns appear at higher Darcy and Rayleigh numbers and lower Biot numbers[ Results are presented for a Darcy number range of 09 -6 Ð09 -1 \ Rayleigh number range of 09 1 Ð09 8 and aspect ratios from 0 to 09[ Þ 0887 Elsevier Science Ltd[ All rights reserved[ Nomenclature A aspect ratio "H:L# Bi Biot number c p speci_c heat Da Darcy number `acceleration due to gravity H height of the porous cavity h convective heat transfer coe.cient J viscosity ratio k average thermal conductivity "ok f ¦"0-o#k s # k conductivity ratio "k:k f # L characteristic dimension Nu average Nusselt number p pressure Pr Prandtl number Ra Rayleigh number T temperature t time u\ v velocity components =V Þ = total velocity vector x\ y coordinate axes[
Development of a PLIC-VOF method for the dynamic simulation of entry region flow in a laminar falling film
International Journal of Computational Fluid Dynamics, 2009
The present work describes a numerical procedure to simulate the development of hydrodynamic entr... more The present work describes a numerical procedure to simulate the development of hydrodynamic entry region in a gravity-driven laminar liquid film flow over an inclined plane. It provides a better insight into the physics of developing film in entry region. A novel numerical approach is proposed which has the potential to provide solutions for the complex physics of liquid film
Non-Newtonian blood flow study in a model cavopulmonary vascular system
International Journal for Numerical Methods in Fluids, 2011
ABSTRACT
Communications in Numerical Methods in Engineering, 2009
The complexities in the flow pattern in a cavo-pulmonary vascular system-after application of the... more The complexities in the flow pattern in a cavo-pulmonary vascular system-after application of the Fontan procedure in the vicinity of the superior vena cava, inferior vena cava, and the confluence at the Tjunction-are analysed. A characteristic-based split (CBS) finite element scheme involving the artificial compressibility approach is employed to compute the resulting flow. Benchmarking of the CBS scheme is carried out using standard problems and with the flow features observed in an experimental model with the help of a dye visualization technique in model scale. The transient flow variations in a total cavo-pulmonary connection (TCPC) under pulsatile conditions are investigated and compared with flow visualization studies. In addition to such qualitative flow investigations, quantitative analysis of energy loss and haemodynamic stresses have also been performed. The comparisons show good agreement between the numerical and experimental flow patterns. The numerically predicted shear stress values indicate that the pulsatile flow condition is likely to be more severe than steady flow, with regard to the long-term health of the surgically corrected TCPC.
Numerical simulation of natural convective heat transfer and fluid flow around a heated cylinder inside an enclosure
Heat and Mass Transfer, 2002
A collocated, non-orthogonal grid based finite volume technique has been applied for investigatin... more A collocated, non-orthogonal grid based finite volume technique has been applied for investigating the two dimensional natural convective flow and heat transfer around a heated cylinder kept in a square enclosure. The effects of different enclosure wall thermal boundary conditions, fluid Prandtl number and the ratio between enclosure and cylinder dimensions (aspect ratio) upon the flow and thermal features, have
Investigation of interaction between methanol fed tandem porous spheres burning in a mixed convective environment
Combustion Theory and Modelling, 2009
... Combust. Inst., 26 (1996), pp. 16971704. [25] P. Balakrishnan, T. Sundararajan and R. Natara... more ... Combust. Inst., 26 (1996), pp. 16971704. [25] P. Balakrishnan, T. Sundararajan and R. Natarajan, Interference effects during burning of tandem porous spheres in mixed convective environment, AIAA Journal, 38 (2000), pp. 18891898. ...
The Canadian Journal of Chemical Engineering, 1993
The slow non‐Newtonian (inelastic) flow through packed beds of mono‐size spherical particles has ... more The slow non‐Newtonian (inelastic) flow through packed beds of mono‐size spherical particles has been simulated by solving the equations of motion numerically. The inter‐particle interactions have been modelled by using a simple cell model. Theoretical estimates of pressure, friction and total drag coefficients as function of the pertinent physical (l≥n≥ 0.2; 0.3 ≤ e ≤ 0.5) and kinematic parameters (0.01 ≤ '≤ 100) for a fixed value of Reynolds number {Re = 0.001) have been obtained. The theoretical predictions reported herein have been validated using the suitable experimental results available in the literature, and the importance of including the zero shear viscosity in analyses for the creeping flow problems is convincingly demonstrated.
Bulletin of Materials Science, 2008
This work presents a simple model for predicting the thermal conductivity of carbon nanotube (CNT... more This work presents a simple model for predicting the thermal conductivity of carbon nanotube (CNT) nanofluids. Effects due to the high thermal conductivity of CNTs and the percolation of heat through it are considered to be the most important reasons for their anomalously high thermal conductivity enhancement. A new approach is taken for the modeling, the novelty of which lies in the prediction of the thermal behaviour of oil based as well as water based CNT nanofluids, which are quite different from each other in thermal characteristics. The model is found to correctly predict the trends observed in experimental data for different combinations of CNT nanofluids with varying concentrations.
Annals of Nuclear Energy, 2014
Three-dimensional flow and temperature fields within a 19-pin wire-wrapped fuel bundle of fast re... more Three-dimensional flow and temperature fields within a 19-pin wire-wrapped fuel bundle of fast reactor with internal blockage have been predicted by Computational fluid dynamic (CFD) studies. Simulations are carried out for a stream-wise length of seven helical pitches. Blockage geometry (shape and size), its radial position and blockage porosity which influence the clad temperature and hence increase the risk of sodium boiling, are systematically varied in a parametric study. Clad temperature, cross-stream sodium velocity and cross-stream temperature distributions are investigated in detail. Axial variation of clad temperature is seen to exhibit strong fluctuations due to the interaction of helical spacer wire and coolant flow through a subassembly with porous blockage. The maximum difference in the circumferential temperature of clad, which is a critical parameter for fuel pin mechanical design, is large in pins that are partially exposed to blockage. Effect of porous blockage is found to be limited to the porous zone and the peak clad temperature is proportional to the volume of the porous zone. Peak temperature in the blockage is strongly influenced by the radial extent of blockage and it is higher if the radial extent is larger. Maximum difference in the circumferential clad temperature is relatively low for a corner blockage compared to that of a central blockage. Sodium boiling is imminent in fuel pin bundle with six blocked sub-channels located at the centre when porosity value reduces below 45%.
Characterization of sodium flow over hexagonal fuel subassemblies
International Communications in Heat and Mass Transfer, 2011
Steady flow of liquid sodium over a bundle of heat generating hexagonal subassemblies has been in... more Steady flow of liquid sodium over a bundle of heat generating hexagonal subassemblies has been investigated. The cross flow pressure drop and heat transfer are characterized using the general purpose CFD code STAR-CD. Analysis has been carried out for both laminar and ...
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Papers by Prof. T Sundararajan Sundararajan