Numerical Heat Transfer, Part A: Applications, 2009
Phase change phenomena occur in many important engineering applications such as material processi... more Phase change phenomena occur in many important engineering applications such as material processing, continuous casting, cladding, crystal growth, etc. In some of the processes, metals or semiconductors in the form of solid particles of different shapes or pellets are melted ...
Numerical Heat Transfer, Part A: Applications, 2006
A two-dimensional model has been developed for the blown-powder laser cladding process to study t... more A two-dimensional model has been developed for the blown-powder laser cladding process to study the influence of Marangoni-Benard and Rayleigh-Benard convection on the process parameters: average dilution, maximum and average melt pool temperatures. ...
International Journal of Heat and Mass Transfer, 1993
A three-dimensional conduction model has been developed to predict the temperature distribution i... more A three-dimensional conduction model has been developed to predict the temperature distribution inside the solid and the shape of a groove formed by partial evaporation of a semi-infinite body using a moving CW laser with a Gaussian beam profile. This has application in laser ...
A three-dimensional conduction model was developed to predict the shape of a groove formed by par... more A three-dimensional conduction model was developed to predict the shape of a groove formed by partially evaporating the surface of a semiinfinite body using a moving Gaussian laser beam. The boundary element method was used to solve the full three-dimensional ...
Beam guiding effects during laser machining of ceramics due to multiple reflections in the groove... more Beam guiding effects during laser machining of ceramics due to multiple reflections in the groove are analyzed theoretically for two extreme cases—purely specular and purely diffuse reflections. Specular reflections are valid for materials that have a smooth surface during ...
Laminar natural convection has been studied in a laterally heated vertical cylindrical enclosure ... more Laminar natural convection has been studied in a laterally heated vertical cylindrical enclosure with a free insulated surface and a centrally located constant temperature wall at the top. These conditions are a simplification of the conditions existing in a Czochralski crystal pulling system. The laminar, axisymmetric flow of a Newtonian, constant physical properties fluid under Boussinesq’s approximation has been considered. Governing equations in primitive variable form are solved numerically by control volume method. SIMPLE algorithm due to Patankar has been used for the numerical simulation. The effects of the constant wall heat flux boundary condition at the side wall have been investigated whereas the bottom wall is considered to be insulated. Streamlines and isotherms are presented for various Rayleigh numbers and Prandtl numbers. Heat flux vectors through the melt are plotted for selected cases. The axial velocity and temperature variations at different horizontal sections of the crucible have been presented graphically to explain the transport processes inside the crucible. It has been observed that in case of low Pr and high Ra, flow separation occurs at the vertical wall of the crucible which leads to an oscillatory flow as Ra increases. The investigation has been extended to the oscillatory regime of flow in the zone of supercritical Rayleigh numbers and some unsteady results are also presented. Finally a heat transfer correlation has been developed for steady-state case.
A two-dimensional model has been developed for the blown-powder laser cladding process to study t... more A two-dimensional model has been developed for the blown-powder laser cladding process to study the influence of Marangoni-Benard and Rayleigh-Benard convection on the process parameters: average dilution, maximum and average melt pool temperatures. ...
Cladding is the process of depositing a superior built-up layer by fusion on a substrate. In blow... more Cladding is the process of depositing a superior built-up layer by fusion on a substrate. In blown powder laser cladding process, the powder travels across the laser path, gets heated up by absorbing laser energy, and finally melts on the substrate under the intense laser beam; as the ...
A three-dimensional heat transfer model is developed to simulate the cladding process that includ... more A three-dimensional heat transfer model is developed to simulate the cladding process that include the different physical phenomena such as heat transfer, phase changes, addition of powder particles and fluid flow due to MarangoniRayleighBenard convection. It is found that the ...
Phase change phenomena occur in many important engineering applications such as material processi... more Phase change phenomena occur in many important engineering applications such as material processing, continuous casting, cladding, crystal growth, etc. In some of the processes, metals or semiconductors in the form of solid particles of different shapes or pellets are melted ...
In blown powder laser cladding process, the powder travels across the laser path, gets heated up ... more In blown powder laser cladding process, the powder travels across the laser path, gets heated up by absorbing laser energy, and finally melts on the substrate under the intense laser beam; as the substrate moves away this melt pool solidifies to form a continuous built-up ...
There are manufacturing applications like surface modification and repair technologies where meta... more There are manufacturing applications like surface modification and repair technologies where metal particles go into the superheated melt pool heated by an intense heat source and as the workpiece moves away from the energy source this pool solidifies to form a continuous ...
In the present study laminar transition to oscillatory convection of fluids having different Pran... more In the present study laminar transition to oscillatory convection of fluids having different Prandtl numbers in a laterally heated vertical cylindrical enclosure for different aspect ratios (melt height to crucible radius) of 2–4 is investigated numerically for 0.01 ≤ Pr ≤ 10. Numerical solution to two-dimensional axisymmetric transient Navier Stokes equations and energy equation were solved by finite volume method using SIMPLE algorithm. Numerical results illustrate that there exists a critical Rayleigh number for each Prandtl number beyond which sustained laminar oscillatory flow sets in. The oscillatory regime was characterised by the oscillation of the average kinetic energy and average thermal energy of the melt. For a given aspect ratio, critical Rayleigh number increases with Pr upto 1 and then flattens. It was observed that for low Prandtl number fluids, Pr Pr ≥ 1.0, it is found to decrease with increase in aspect ratio. The influence of aspect ratio on the transient behaviour of the melt volume below and above the critical Rayleigh number was studied.
Numerical Heat Transfer, Part A: Applications, 2009
Phase change phenomena occur in many important engineering applications such as material processi... more Phase change phenomena occur in many important engineering applications such as material processing, continuous casting, cladding, crystal growth, etc. In some of the processes, metals or semiconductors in the form of solid particles of different shapes or pellets are melted ...
Numerical Heat Transfer, Part A: Applications, 2006
A two-dimensional model has been developed for the blown-powder laser cladding process to study t... more A two-dimensional model has been developed for the blown-powder laser cladding process to study the influence of Marangoni-Benard and Rayleigh-Benard convection on the process parameters: average dilution, maximum and average melt pool temperatures. ...
International Journal of Heat and Mass Transfer, 1993
A three-dimensional conduction model has been developed to predict the temperature distribution i... more A three-dimensional conduction model has been developed to predict the temperature distribution inside the solid and the shape of a groove formed by partial evaporation of a semi-infinite body using a moving CW laser with a Gaussian beam profile. This has application in laser ...
A three-dimensional conduction model was developed to predict the shape of a groove formed by par... more A three-dimensional conduction model was developed to predict the shape of a groove formed by partially evaporating the surface of a semiinfinite body using a moving Gaussian laser beam. The boundary element method was used to solve the full three-dimensional ...
Beam guiding effects during laser machining of ceramics due to multiple reflections in the groove... more Beam guiding effects during laser machining of ceramics due to multiple reflections in the groove are analyzed theoretically for two extreme cases—purely specular and purely diffuse reflections. Specular reflections are valid for materials that have a smooth surface during ...
Laminar natural convection has been studied in a laterally heated vertical cylindrical enclosure ... more Laminar natural convection has been studied in a laterally heated vertical cylindrical enclosure with a free insulated surface and a centrally located constant temperature wall at the top. These conditions are a simplification of the conditions existing in a Czochralski crystal pulling system. The laminar, axisymmetric flow of a Newtonian, constant physical properties fluid under Boussinesq’s approximation has been considered. Governing equations in primitive variable form are solved numerically by control volume method. SIMPLE algorithm due to Patankar has been used for the numerical simulation. The effects of the constant wall heat flux boundary condition at the side wall have been investigated whereas the bottom wall is considered to be insulated. Streamlines and isotherms are presented for various Rayleigh numbers and Prandtl numbers. Heat flux vectors through the melt are plotted for selected cases. The axial velocity and temperature variations at different horizontal sections of the crucible have been presented graphically to explain the transport processes inside the crucible. It has been observed that in case of low Pr and high Ra, flow separation occurs at the vertical wall of the crucible which leads to an oscillatory flow as Ra increases. The investigation has been extended to the oscillatory regime of flow in the zone of supercritical Rayleigh numbers and some unsteady results are also presented. Finally a heat transfer correlation has been developed for steady-state case.
A two-dimensional model has been developed for the blown-powder laser cladding process to study t... more A two-dimensional model has been developed for the blown-powder laser cladding process to study the influence of Marangoni-Benard and Rayleigh-Benard convection on the process parameters: average dilution, maximum and average melt pool temperatures. ...
Cladding is the process of depositing a superior built-up layer by fusion on a substrate. In blow... more Cladding is the process of depositing a superior built-up layer by fusion on a substrate. In blown powder laser cladding process, the powder travels across the laser path, gets heated up by absorbing laser energy, and finally melts on the substrate under the intense laser beam; as the ...
A three-dimensional heat transfer model is developed to simulate the cladding process that includ... more A three-dimensional heat transfer model is developed to simulate the cladding process that include the different physical phenomena such as heat transfer, phase changes, addition of powder particles and fluid flow due to MarangoniRayleighBenard convection. It is found that the ...
Phase change phenomena occur in many important engineering applications such as material processi... more Phase change phenomena occur in many important engineering applications such as material processing, continuous casting, cladding, crystal growth, etc. In some of the processes, metals or semiconductors in the form of solid particles of different shapes or pellets are melted ...
In blown powder laser cladding process, the powder travels across the laser path, gets heated up ... more In blown powder laser cladding process, the powder travels across the laser path, gets heated up by absorbing laser energy, and finally melts on the substrate under the intense laser beam; as the substrate moves away this melt pool solidifies to form a continuous built-up ...
There are manufacturing applications like surface modification and repair technologies where meta... more There are manufacturing applications like surface modification and repair technologies where metal particles go into the superheated melt pool heated by an intense heat source and as the workpiece moves away from the energy source this pool solidifies to form a continuous ...
In the present study laminar transition to oscillatory convection of fluids having different Pran... more In the present study laminar transition to oscillatory convection of fluids having different Prandtl numbers in a laterally heated vertical cylindrical enclosure for different aspect ratios (melt height to crucible radius) of 2–4 is investigated numerically for 0.01 ≤ Pr ≤ 10. Numerical solution to two-dimensional axisymmetric transient Navier Stokes equations and energy equation were solved by finite volume method using SIMPLE algorithm. Numerical results illustrate that there exists a critical Rayleigh number for each Prandtl number beyond which sustained laminar oscillatory flow sets in. The oscillatory regime was characterised by the oscillation of the average kinetic energy and average thermal energy of the melt. For a given aspect ratio, critical Rayleigh number increases with Pr upto 1 and then flattens. It was observed that for low Prandtl number fluids, Pr Pr ≥ 1.0, it is found to decrease with increase in aspect ratio. The influence of aspect ratio on the transient behaviour of the melt volume below and above the critical Rayleigh number was studied.
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