Anantha Krishnan - Academia.edu (original) (raw)

Papers by Anantha Krishnan

Research paper thumbnail of Impact of correct and simulated focus cues on perceived realism

SIGGRAPH Asia 2022 Conference Papers

We compared the realism of a 3-dimensional scene reproduced with near-correct focus cues (NearCor... more We compared the realism of a 3-dimensional scene reproduced with near-correct focus cues (NearCorrect), as a stereo image with incorrect focus cues (Stereo), and as a stereo image with three types of defocus blur simulation (ChromaBlur, RetinalBlur, FakeBlur). We found that focus cues have a significant effect on realism and that replacing natural defocus with depth-of-field effect simulation degrades realism instead of improving it.

Research paper thumbnail of An Implicit Numerical Model for Electrophoretic Systems

Micro-Electro-Mechanical Systems (MEMS), 1998

An implicit finite-volume approach has been developed to solve the equations governing the electr... more An implicit finite-volume approach has been developed to solve the equations governing the electrophoretic process. The numerical procedure involves the sequential solution of the species conservation ionization equilibria and electro-neutrality equations in an iterative fashion until convergence. This implicit procedure is numerically stable and allows for faster steady-state solutions or larger time steps for time-accurate simulations. Temporal evolutions of pH, species concentrations and electrolyte conductivity are predicted. The results obtained using various higher order numerical schemes are compared and assessed. Results are presented for the isoelectric focussing, moving boundary electrophoresis, and capillary electrophoresis of amino acids and a protein. The predictions for the isoelectric focussing of albumin protein are in qualitative agreement with published experimental data.

Research paper thumbnail of Flow-Combustion Interactions in a Turbulent Jet

Dynamics of Deflagrations and Reactive Systems: Flames, 1991

Abstract The interactions between the flowfield and the combustion process in a reacting jet are ... more Abstract The interactions between the flowfield and the combustion process in a reacting jet are analyzed using numerical simulations. Computational results are obtained for the compressible flow model of low-Mach-number combustion using the vortex/transport ...

Research paper thumbnail of Dispositif de sécurité d'intrusion avec commande et notification à base de sms

Research paper thumbnail of Einbruchsicherheitsvorrichtung mit sms-basierter benachrichtigung und steuerung

Research paper thumbnail of Localising the Circular Economy: short green value chains for protecting the environment while catering for a growing population

The session aims to bring key urban stakeholders together to establish dialogue on cities and cir... more The session aims to bring key urban stakeholders together to establish dialogue on cities and circular economies. City leaders, urban professionals, financial institutions, community groups and academics will come together to present good and replicable examples and discuss practical approaches to implementing circular economies. The session will provide thoughts for decoupling economic activity from the consumption of finite resources locally and globally, and reducing waste out of the system - maximizing the value of resources by keeping them in use for as long as possible.

Research paper thumbnail of Late Advances in the Field of Low-Vision Telescopes and Distance Magnifiers: A Review

International Journal of Psychosocial Rehabilitation, 2020

Research paper thumbnail of Enhancing the thermophysical properties of PAG lubricant using graphene nano-sheets

Journal of Physics: Conference Series, 2019

One of the most attractive methods to improve the thermo physical and heat transfer properties of... more One of the most attractive methods to improve the thermo physical and heat transfer properties of conventional coolants and lubricants is the use of nanoparticles in it. Nanofluids are stable colloidal suspensions of nanoparticles and base fluids. The nanofluids exhibit superior thermal performance compared to conventional heat transfer fluids and this leads to the best hope for lubricants based nanofluids as well. Nanolubricant is a new class of lubricant produced by dispersing nano-sized particles of metals, metal oxides, carbon and its allotropes into conventional lubricating oils. In the present study, experiments were conducted to measure the thermophysical and rheological properties of polyalkyleneglycol (PAG) refrigerant compressor oil suspended with graphene nano-sheets. The effect of particle concentration and temperature on thermal conductivity and viscosity of nanolubricant were elucidated. The volume fraction is varied from 0.05 to 0.8% and the temperature range is from ...

Research paper thumbnail of A numerical model for atomization-spray coupling in liquid rocket thrust chambers

The physical process of atomization is an important consideration in the stable operation of liqu... more The physical process of atomization is an important consideration in the stable operation of liquid rocket engines. Many spray combustion computational fluid dynamics (CFD) codes do not include an atomization sub-model but assume arbitrary drop size distributions, drop initial locations, and velocities. A method of coupling an atomization model with the spray model in a REFLEQS CFD code is presented.

Research paper thumbnail of <title>Preliminary study of the influence of Grashof and Reynolds numbers on the flow and heat transfer in an MOCVD reactor</title>

Materials Research in Low Gravity, 1997

The combined effect of Grashof and Reynolds numbers on the flow and heat transfer in a metal orga... more The combined effect of Grashof and Reynolds numbers on the flow and heat transfer in a metal organic chemical vapor deposition (MOCVD) reactor is investigated both experimentally and numerically. Experimental data for pure hydrogen, helium, and nitrogen with induction heating are obtained at the Chemical Vapor Deposition Facility for Reactor Characterization at NASA Langley Research Center (LaRC). The test facility measures the velocity field inside the reactor using a three dimensional laser velocimeter. Temperatures of the fused silica walls are recorded using an infrared camera. Each gas is tested over a range of flow rates. These experimental runs are repeated using a three-dimensional computational fluid dynamics code which models the flow and heat transport throughout the reactor. The model accounts for the mechanisms of conjugate heat conduction, convection, and radiation. The analytical results are compared with the experimental data and used to assess the heat and mass transfer in the system as a function of the Richardson number, Ri equals Gr/Re2.

Research paper thumbnail of <title>Development of an advanced computational model for OMCVD of indium nitride</title>

Physics and Simulation of Optoelectronic Devices VII, 1999

ABSTRACT

Research paper thumbnail of Thermal cracking of Norpar-13 under near-critical and supercritical conditions

34th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, 1998

A three-step global model is developed to describe the thermal cracking of Norpar-13 under superc... more A three-step global model is developed to describe the thermal cracking of Norpar-13 under supercritical and near-critical conditions. This cracking model is incorporated into a multi-dimensional Computational Fluid Dynamics (CFD) code to simulate the heat/mass transfer and thermal cracking of Norpar-13 in flow systems. The proposed model is tested against the experimental data measured at different temperatures and residence times. Agreement is obtained when comparing the simulations results with measurements. The endothermic effect of Norpar-13 thermal cracking is analyzed using the validated cracking model. The results show that the energy absorbed by the cracking reactions has importance consequence in reducing the fuel and wall temperature although it only accounts for a small portion of total input power.

Research paper thumbnail of On mixing, baroclinicity, and the effect of strain in a chemically-reacting shear layer

26th Aerospace Sciences Meeting, 1988

Numerical simulation, using the transport element method, is applied to study mixing of a passive... more Numerical simulation, using the transport element method, is applied to study mixing of a passive scalar in a spatially-developing shear layer, and to investigate the interaction between the flow and the chemical reaction in a temporally-growing, premixed shear layer. In the first case, ...

Research paper thumbnail of CFD simulation of pulsed MOCVD to reduce gas-phase parasitic reaction

SPIE Proceedings, 1999

A Computational Fluid Dynamics (CFD) code is used to determine the potential benefit of pulsed Me... more A Computational Fluid Dynamics (CFD) code is used to determine the potential benefit of pulsed Metal-Organic Chemical Vapor Deposition (MOCVD). When AlN is grown using MOCVD over a range of pressures (30 to 270 Torr) and substrate temperatures (400°C to 900°C), gas-...

Research paper thumbnail of Numerical simulation of crystal growth by physical vapor transport in microgravity environments

33rd Aerospace Sciences Meeting and Exhibit, 1995

A physical model to simulate steady-state crystal growth by Physical Vapor Transport (PVT), has b... more A physical model to simulate steady-state crystal growth by Physical Vapor Transport (PVT), has been implemented in a general purpose computational fluid dynamics (CFD) code. The effects of microgravity environment on the PVT process was investigated through numerical studies of a binary system of Iodine and Hydrogen. The numerical results reveal that gravity will enhance the overall growth rate due to increased transport by buoyancy-driven convection, but the uniformity of the crystal growth surface is poor. On the other hand, the microgravity environment reduces buoyancy- driven convection and the resulting unidirectional (purely diffusive) flow leads to enhanced uniformity. Numerical simulations show that different gravity levels are required (for different PVT ampoule geometries) to achieve a pure diffusive flow, and a criterion for this flow condition has been derived numerically. This article demonstrates that numerical simulations are useful in determining optimal conditions for crystal growth by PVT. v

Research paper thumbnail of A numerical model for endothermic fuel flows with heterogeneous catalysis

34th Aerospace Sciences Meeting and Exhibit, 1996

This article describes a numerical model to simulate heat/mass transfer and heterogeneous catalys... more This article describes a numerical model to simulate heat/mass transfer and heterogeneous catalysis in endothermic fuel flows. The models for heterogeneous catalysis and thermophysical properties of (supercritical) hydrocarbon mixtures are incorporated into a multidimensional CFD ...

Research paper thumbnail of Calibration of a global mechanism for jet fuel deposition

32nd Joint Propulsion Conference and Exhibit, 1996

A nine-step mechanism calibrated for Jet-A fuel deposition is incorporated into a general purpose... more A nine-step mechanism calibrated for Jet-A fuel deposition is incorporated into a general purpose CFD code, CFD-ACE, to simulate deposition and coking in fuel systems of high performance aircraft. CFD-ACE has a generalized model to compute thermophysical properties of gas ...

Research paper thumbnail of Numerical simulation of a reacting shear layer using the transport element method

23rd Joint Propulsion Conference, 1987

The transport element method, a numerical scheme that combines the vortex method with the Lagrang... more The transport element method, a numerical scheme that combines the vortex method with the Lagrangian transport of scalar gradients, is used to study the evolution of combustion in a reacting shear layer. The scheme is based on the accurate discretization of the vorticity and the ...

Research paper thumbnail of <title>Modeling of thermal field in contactless physical vapor transport system</title>

Materials Research in Low Gravity, 1997

A numerical model of the thermal field in the furnace-ampoule system developed for the 'conta... more A numerical model of the thermal field in the furnace-ampoule system developed for the 'contactless' physical vapor transport growth geometry is presented. The model is used to assess the effect of the system geometry and growth parameters on the conditions of 'contactless' growth of cadmium telluride crystals.

Research paper thumbnail of Synchrotron-based Ambient Pressure X-ray Photoelectron Spectroscopy

Synchrotron Radiation News, 2014

Contrary to popular belief, it is possible to obtain X-ray photoelectron spectra for elements lig... more Contrary to popular belief, it is possible to obtain X-ray photoelectron spectra for elements lighter than lithium, namely hydrogen and helium. The literature is plagued with claims of this impossibility, which holds true for lab-based X-ray sources. However, this limitation is merely technical and relates mostly to the low X-ray photoionization cross sections of the 1s orbitals of hydrogen and helium. In this letter we show that, using ambient pressure X-ray photoelectron spectroscopy (XPS), a bright-enough X-ray source allows the study of these elusive elements. This has important implications in the understanding of the limitations of one of the most useful techniques in materials science and moreover, it potentially opens the possibility of using XPS to directly study the most abundant element in the universe.

Research paper thumbnail of Impact of correct and simulated focus cues on perceived realism

SIGGRAPH Asia 2022 Conference Papers

We compared the realism of a 3-dimensional scene reproduced with near-correct focus cues (NearCor... more We compared the realism of a 3-dimensional scene reproduced with near-correct focus cues (NearCorrect), as a stereo image with incorrect focus cues (Stereo), and as a stereo image with three types of defocus blur simulation (ChromaBlur, RetinalBlur, FakeBlur). We found that focus cues have a significant effect on realism and that replacing natural defocus with depth-of-field effect simulation degrades realism instead of improving it.

Research paper thumbnail of An Implicit Numerical Model for Electrophoretic Systems

Micro-Electro-Mechanical Systems (MEMS), 1998

An implicit finite-volume approach has been developed to solve the equations governing the electr... more An implicit finite-volume approach has been developed to solve the equations governing the electrophoretic process. The numerical procedure involves the sequential solution of the species conservation ionization equilibria and electro-neutrality equations in an iterative fashion until convergence. This implicit procedure is numerically stable and allows for faster steady-state solutions or larger time steps for time-accurate simulations. Temporal evolutions of pH, species concentrations and electrolyte conductivity are predicted. The results obtained using various higher order numerical schemes are compared and assessed. Results are presented for the isoelectric focussing, moving boundary electrophoresis, and capillary electrophoresis of amino acids and a protein. The predictions for the isoelectric focussing of albumin protein are in qualitative agreement with published experimental data.

Research paper thumbnail of Flow-Combustion Interactions in a Turbulent Jet

Dynamics of Deflagrations and Reactive Systems: Flames, 1991

Abstract The interactions between the flowfield and the combustion process in a reacting jet are ... more Abstract The interactions between the flowfield and the combustion process in a reacting jet are analyzed using numerical simulations. Computational results are obtained for the compressible flow model of low-Mach-number combustion using the vortex/transport ...

Research paper thumbnail of Dispositif de sécurité d'intrusion avec commande et notification à base de sms

Research paper thumbnail of Einbruchsicherheitsvorrichtung mit sms-basierter benachrichtigung und steuerung

Research paper thumbnail of Localising the Circular Economy: short green value chains for protecting the environment while catering for a growing population

The session aims to bring key urban stakeholders together to establish dialogue on cities and cir... more The session aims to bring key urban stakeholders together to establish dialogue on cities and circular economies. City leaders, urban professionals, financial institutions, community groups and academics will come together to present good and replicable examples and discuss practical approaches to implementing circular economies. The session will provide thoughts for decoupling economic activity from the consumption of finite resources locally and globally, and reducing waste out of the system - maximizing the value of resources by keeping them in use for as long as possible.

Research paper thumbnail of Late Advances in the Field of Low-Vision Telescopes and Distance Magnifiers: A Review

International Journal of Psychosocial Rehabilitation, 2020

Research paper thumbnail of Enhancing the thermophysical properties of PAG lubricant using graphene nano-sheets

Journal of Physics: Conference Series, 2019

One of the most attractive methods to improve the thermo physical and heat transfer properties of... more One of the most attractive methods to improve the thermo physical and heat transfer properties of conventional coolants and lubricants is the use of nanoparticles in it. Nanofluids are stable colloidal suspensions of nanoparticles and base fluids. The nanofluids exhibit superior thermal performance compared to conventional heat transfer fluids and this leads to the best hope for lubricants based nanofluids as well. Nanolubricant is a new class of lubricant produced by dispersing nano-sized particles of metals, metal oxides, carbon and its allotropes into conventional lubricating oils. In the present study, experiments were conducted to measure the thermophysical and rheological properties of polyalkyleneglycol (PAG) refrigerant compressor oil suspended with graphene nano-sheets. The effect of particle concentration and temperature on thermal conductivity and viscosity of nanolubricant were elucidated. The volume fraction is varied from 0.05 to 0.8% and the temperature range is from ...

Research paper thumbnail of A numerical model for atomization-spray coupling in liquid rocket thrust chambers

The physical process of atomization is an important consideration in the stable operation of liqu... more The physical process of atomization is an important consideration in the stable operation of liquid rocket engines. Many spray combustion computational fluid dynamics (CFD) codes do not include an atomization sub-model but assume arbitrary drop size distributions, drop initial locations, and velocities. A method of coupling an atomization model with the spray model in a REFLEQS CFD code is presented.

Research paper thumbnail of <title>Preliminary study of the influence of Grashof and Reynolds numbers on the flow and heat transfer in an MOCVD reactor</title>

Materials Research in Low Gravity, 1997

The combined effect of Grashof and Reynolds numbers on the flow and heat transfer in a metal orga... more The combined effect of Grashof and Reynolds numbers on the flow and heat transfer in a metal organic chemical vapor deposition (MOCVD) reactor is investigated both experimentally and numerically. Experimental data for pure hydrogen, helium, and nitrogen with induction heating are obtained at the Chemical Vapor Deposition Facility for Reactor Characterization at NASA Langley Research Center (LaRC). The test facility measures the velocity field inside the reactor using a three dimensional laser velocimeter. Temperatures of the fused silica walls are recorded using an infrared camera. Each gas is tested over a range of flow rates. These experimental runs are repeated using a three-dimensional computational fluid dynamics code which models the flow and heat transport throughout the reactor. The model accounts for the mechanisms of conjugate heat conduction, convection, and radiation. The analytical results are compared with the experimental data and used to assess the heat and mass transfer in the system as a function of the Richardson number, Ri equals Gr/Re2.

Research paper thumbnail of <title>Development of an advanced computational model for OMCVD of indium nitride</title>

Physics and Simulation of Optoelectronic Devices VII, 1999

ABSTRACT

Research paper thumbnail of Thermal cracking of Norpar-13 under near-critical and supercritical conditions

34th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, 1998

A three-step global model is developed to describe the thermal cracking of Norpar-13 under superc... more A three-step global model is developed to describe the thermal cracking of Norpar-13 under supercritical and near-critical conditions. This cracking model is incorporated into a multi-dimensional Computational Fluid Dynamics (CFD) code to simulate the heat/mass transfer and thermal cracking of Norpar-13 in flow systems. The proposed model is tested against the experimental data measured at different temperatures and residence times. Agreement is obtained when comparing the simulations results with measurements. The endothermic effect of Norpar-13 thermal cracking is analyzed using the validated cracking model. The results show that the energy absorbed by the cracking reactions has importance consequence in reducing the fuel and wall temperature although it only accounts for a small portion of total input power.

Research paper thumbnail of On mixing, baroclinicity, and the effect of strain in a chemically-reacting shear layer

26th Aerospace Sciences Meeting, 1988

Numerical simulation, using the transport element method, is applied to study mixing of a passive... more Numerical simulation, using the transport element method, is applied to study mixing of a passive scalar in a spatially-developing shear layer, and to investigate the interaction between the flow and the chemical reaction in a temporally-growing, premixed shear layer. In the first case, ...

Research paper thumbnail of CFD simulation of pulsed MOCVD to reduce gas-phase parasitic reaction

SPIE Proceedings, 1999

A Computational Fluid Dynamics (CFD) code is used to determine the potential benefit of pulsed Me... more A Computational Fluid Dynamics (CFD) code is used to determine the potential benefit of pulsed Metal-Organic Chemical Vapor Deposition (MOCVD). When AlN is grown using MOCVD over a range of pressures (30 to 270 Torr) and substrate temperatures (400°C to 900°C), gas-...

Research paper thumbnail of Numerical simulation of crystal growth by physical vapor transport in microgravity environments

33rd Aerospace Sciences Meeting and Exhibit, 1995

A physical model to simulate steady-state crystal growth by Physical Vapor Transport (PVT), has b... more A physical model to simulate steady-state crystal growth by Physical Vapor Transport (PVT), has been implemented in a general purpose computational fluid dynamics (CFD) code. The effects of microgravity environment on the PVT process was investigated through numerical studies of a binary system of Iodine and Hydrogen. The numerical results reveal that gravity will enhance the overall growth rate due to increased transport by buoyancy-driven convection, but the uniformity of the crystal growth surface is poor. On the other hand, the microgravity environment reduces buoyancy- driven convection and the resulting unidirectional (purely diffusive) flow leads to enhanced uniformity. Numerical simulations show that different gravity levels are required (for different PVT ampoule geometries) to achieve a pure diffusive flow, and a criterion for this flow condition has been derived numerically. This article demonstrates that numerical simulations are useful in determining optimal conditions for crystal growth by PVT. v

Research paper thumbnail of A numerical model for endothermic fuel flows with heterogeneous catalysis

34th Aerospace Sciences Meeting and Exhibit, 1996

This article describes a numerical model to simulate heat/mass transfer and heterogeneous catalys... more This article describes a numerical model to simulate heat/mass transfer and heterogeneous catalysis in endothermic fuel flows. The models for heterogeneous catalysis and thermophysical properties of (supercritical) hydrocarbon mixtures are incorporated into a multidimensional CFD ...

Research paper thumbnail of Calibration of a global mechanism for jet fuel deposition

32nd Joint Propulsion Conference and Exhibit, 1996

A nine-step mechanism calibrated for Jet-A fuel deposition is incorporated into a general purpose... more A nine-step mechanism calibrated for Jet-A fuel deposition is incorporated into a general purpose CFD code, CFD-ACE, to simulate deposition and coking in fuel systems of high performance aircraft. CFD-ACE has a generalized model to compute thermophysical properties of gas ...

Research paper thumbnail of Numerical simulation of a reacting shear layer using the transport element method

23rd Joint Propulsion Conference, 1987

The transport element method, a numerical scheme that combines the vortex method with the Lagrang... more The transport element method, a numerical scheme that combines the vortex method with the Lagrangian transport of scalar gradients, is used to study the evolution of combustion in a reacting shear layer. The scheme is based on the accurate discretization of the vorticity and the ...

Research paper thumbnail of <title>Modeling of thermal field in contactless physical vapor transport system</title>

Materials Research in Low Gravity, 1997

A numerical model of the thermal field in the furnace-ampoule system developed for the 'conta... more A numerical model of the thermal field in the furnace-ampoule system developed for the 'contactless' physical vapor transport growth geometry is presented. The model is used to assess the effect of the system geometry and growth parameters on the conditions of 'contactless' growth of cadmium telluride crystals.

Research paper thumbnail of Synchrotron-based Ambient Pressure X-ray Photoelectron Spectroscopy

Synchrotron Radiation News, 2014

Contrary to popular belief, it is possible to obtain X-ray photoelectron spectra for elements lig... more Contrary to popular belief, it is possible to obtain X-ray photoelectron spectra for elements lighter than lithium, namely hydrogen and helium. The literature is plagued with claims of this impossibility, which holds true for lab-based X-ray sources. However, this limitation is merely technical and relates mostly to the low X-ray photoionization cross sections of the 1s orbitals of hydrogen and helium. In this letter we show that, using ambient pressure X-ray photoelectron spectroscopy (XPS), a bright-enough X-ray source allows the study of these elusive elements. This has important implications in the understanding of the limitations of one of the most useful techniques in materials science and moreover, it potentially opens the possibility of using XPS to directly study the most abundant element in the universe.