The Experts below are selected from a list of 1449 Experts worldwide ranked by ideXlab platform

A. Roy Choudhury - One of the best experts on this subject based on the ideXlab platform.

  • A study on laser drilling of thin steel sheet in air and underwater
    Journal of Applied Physics, 2010
    Co-Authors: Ashish Kumar Nath, Dulari Hansdah, A. Roy Choudhury
    Abstract:

    In laser drilling of a thin stainless steel sheet in air with Nd:YAG laser pulses of 0.5–1 ms durations it was observed that the 0.5 ms duration laser pulse was more effective in drilling a through-hole than the relatively longer laser pulses with proportionately more energy. Further, laser drilling could be readily done when the sheet was placed at the focal point of the lens and below it but not above the focal point. On the other hand, the underwater laser drilling could be done when the sheet was placed above the focal point. An attempt has been made to explain these experimental observations considering various processes involved in laser drilling in air and underwater. While the recoil pressure of the vapor and plasma played an important role in laser drilling in air; the radial gradient of recoil pressure of evaporation, the Marangoni Force induced by the surface tension gradient in melt pool and the cavitation effect of bubble collapse were believed to be responsible for the material removal in un...

  • A study on laser drilling of thin steel sheet in air and underwater
    Journal of Applied Physics, 2010
    Co-Authors: Ashish Kumar Nath, Dulari Hansdah, Subhransu Roy, A. Roy Choudhury
    Abstract:

    In laser drilling of a thin stainless steel sheet in air with Nd:YAG laser pulses of 0.5–1 ms durations it was observed that the 0.5 ms duration laser pulse was more effective in drilling a through-hole than the relatively longer laser pulses with proportionately more energy. Further, laser drilling could be readily done when the sheet was placed at the focal point of the lens and below it but not above the focal point. On the other hand, the underwater laser drilling could be done when the sheet was placed above the focal point. An attempt has been made to explain these experimental observations considering various processes involved in laser drilling in air and underwater. While the recoil pressure of the vapor and plasma played an important role in laser drilling in air; the radial gradient of recoil pressure of evaporation, the Marangoni Force induced by the surface tension gradient in melt pool and the cavitation effect of bubble collapse were believed to be responsible for the material removal in underwater drilling process.

S Z Shuja - One of the best experts on this subject based on the ideXlab platform.

  • Marangoni convection flow and heat transfer characteristics of water cnt nanofluid droplets
    Numerical Heat Transfer Part A-applications, 2016
    Co-Authors: Abdullah Alsharafi, Ahmet Z Sahin, B S Yilbas, S Z Shuja
    Abstract:

    ABSTRACTThe heat transfer characteristics of liquid droplets are influenced by the hydrophobicity of the surfaces. Fluid properties and surface energy play important roles in heat transfer assessment. In the present study, the influence of the contact angle on the flow field developed inside a nanofluid droplet consisting of a mixture of water and carbon nanotubes (CNT) is investigated. Flow field and heat transfer characteristics are simulated numerically in line with the experimental conditions. It is found that the flow velocity predicted numerically is in good agreement with the experimental data. Nusselt and Bond numbers increase at large contact angles and Marangoni Force dominates over buoyancy Force.

  • Marangoni convection flow and heat transfer characteristics of water–CNT nanofluid droplets
    Numerical Heat Transfer Part A: Applications, 2016
    Co-Authors: Abdullah Al-sharafi, Ahmet Z Sahin, B S Yilbas, S Z Shuja
    Abstract:

    ABSTRACTThe heat transfer characteristics of liquid droplets are influenced by the hydrophobicity of the surfaces. Fluid properties and surface energy play important roles in heat transfer assessment. In the present study, the influence of the contact angle on the flow field developed inside a nanofluid droplet consisting of a mixture of water and carbon nanotubes (CNT) is investigated. Flow field and heat transfer characteristics are simulated numerically in line with the experimental conditions. It is found that the flow velocity predicted numerically is in good agreement with the experimental data. Nusselt and Bond numbers increase at large contact angles and Marangoni Force dominates over buoyancy Force.

Xinxin Wang - One of the best experts on this subject based on the ideXlab platform.

  • Investigation of heat transfer and fluid flow in high current GTA welding by a unified model
    International Journal of Thermal Sciences, 2019
    Co-Authors: Xinxin Wang, Yi Luo, Ding Fan
    Abstract:

    Abstract This research is aimed to understand the heat transfer and fluid flow of the arc plasma and weld pool with a significant deformation of the weld pool surface during high current gas tungsten arc welding (GTAW). A unified model including the tungsten electrode, arc plasma and the weld pool of low carbon steel is developed by presetting a free surface deformation from the experimental observations. Buoyance, Lorentz Force, plasma drag Force and Marangoni Force are taken into account to investigate the weld pool dynamics with a great depressed free surface. Heat flux, current density, Marangoni Force and plasma drag Force at the weld pool surface are presented to understand the heat and momentum transfer from the arc plasma to the weld pool. It is found that the distributions of the heat flux and current density as well as temperature at the depressed weld pool surface are double-peak profiles; the molten metal flow of the weld pool with severe surface depression are determined by the plasma drag Force rather than the Marangoni Force. The effect of the Lorentz Force is more important than that of the buoyance, but weaker than the Marangoni Force. The results are consistent with the existing results of both the experiment and the theory.

  • Investigation of heat transfer and fluid flow in activating TIG welding by numerical modeling
    Applied Thermal Engineering, 2017
    Co-Authors: Xinxin Wang, Ding Fan, Jiankang Huang, Yong Huang, Yanning Guo
    Abstract:

    Abstract Heat transfer and fluid flow of arc plasma and weld pool in tungsten inert gas (TIG) welding and activated flux tungsten inert gas (A-TIG) welding of SUS 304 stainless steel are investigated comparatively though a 3D unified model. The model differs from the previous ones in that it considers the arc length more realistic for welding production. Tungsten electrode, anode (work piece) and arc plasma are all included. The effects of buoyance, plasma drag Force, Lorentz Force and Marangoni Force on the weld pool flow are taken into account. By solving the conservation equations of mass, momentum, energy as well as Maxwell equations, the distributions of temperature and velocity of arc plasma and weld pool are obtained for TIG and A-TIG welding. The heat flux, current density and shear stress at the weld pool are presented. Dimensionless numbers are employed to compare the relative importance of the driven Forces and that of convection and conduction in heat transfer of the weld pool. It is demonstrated that there is no significant difference in the heat flux at the weld pool, and total heat input to the anode and thermal efficiency is almost equal for TIG and A-TIG welding. The current density and the heat flux at the weld pool are more concentrated in more realistic welding condition. As a result, both of the temperature of the weld pool for TIG welding and A-TIG welding increases, while the latter is more significant. Marangoni Force ranges from zero to 100 Pa and dominant the weld pool flow. Compared with the conventional TIG welding, the reversion of the Marangoni Force results in inward flow and thus causes inward heat convection in weld pool of A-TIG welding. Heat convection was the main mechanism of heat transfer for SUS 304 stainless steel, which results in directly both shallow weld pool shape in TIG welding and remarkably increased weld pool depth and slightly constricted weld pool width in A-TIG welding.

Ding Fan - One of the best experts on this subject based on the ideXlab platform.

  • Investigation of heat transfer and fluid flow in high current GTA welding by a unified model
    International Journal of Thermal Sciences, 2019
    Co-Authors: Xinxin Wang, Yi Luo, Ding Fan
    Abstract:

    Abstract This research is aimed to understand the heat transfer and fluid flow of the arc plasma and weld pool with a significant deformation of the weld pool surface during high current gas tungsten arc welding (GTAW). A unified model including the tungsten electrode, arc plasma and the weld pool of low carbon steel is developed by presetting a free surface deformation from the experimental observations. Buoyance, Lorentz Force, plasma drag Force and Marangoni Force are taken into account to investigate the weld pool dynamics with a great depressed free surface. Heat flux, current density, Marangoni Force and plasma drag Force at the weld pool surface are presented to understand the heat and momentum transfer from the arc plasma to the weld pool. It is found that the distributions of the heat flux and current density as well as temperature at the depressed weld pool surface are double-peak profiles; the molten metal flow of the weld pool with severe surface depression are determined by the plasma drag Force rather than the Marangoni Force. The effect of the Lorentz Force is more important than that of the buoyance, but weaker than the Marangoni Force. The results are consistent with the existing results of both the experiment and the theory.

  • Investigation of heat transfer and fluid flow in activating TIG welding by numerical modeling
    Applied Thermal Engineering, 2017
    Co-Authors: Xinxin Wang, Ding Fan, Jiankang Huang, Yong Huang, Yanning Guo
    Abstract:

    Abstract Heat transfer and fluid flow of arc plasma and weld pool in tungsten inert gas (TIG) welding and activated flux tungsten inert gas (A-TIG) welding of SUS 304 stainless steel are investigated comparatively though a 3D unified model. The model differs from the previous ones in that it considers the arc length more realistic for welding production. Tungsten electrode, anode (work piece) and arc plasma are all included. The effects of buoyance, plasma drag Force, Lorentz Force and Marangoni Force on the weld pool flow are taken into account. By solving the conservation equations of mass, momentum, energy as well as Maxwell equations, the distributions of temperature and velocity of arc plasma and weld pool are obtained for TIG and A-TIG welding. The heat flux, current density and shear stress at the weld pool are presented. Dimensionless numbers are employed to compare the relative importance of the driven Forces and that of convection and conduction in heat transfer of the weld pool. It is demonstrated that there is no significant difference in the heat flux at the weld pool, and total heat input to the anode and thermal efficiency is almost equal for TIG and A-TIG welding. The current density and the heat flux at the weld pool are more concentrated in more realistic welding condition. As a result, both of the temperature of the weld pool for TIG welding and A-TIG welding increases, while the latter is more significant. Marangoni Force ranges from zero to 100 Pa and dominant the weld pool flow. Compared with the conventional TIG welding, the reversion of the Marangoni Force results in inward flow and thus causes inward heat convection in weld pool of A-TIG welding. Heat convection was the main mechanism of heat transfer for SUS 304 stainless steel, which results in directly both shallow weld pool shape in TIG welding and remarkably increased weld pool depth and slightly constricted weld pool width in A-TIG welding.

Ashish Kumar Nath - One of the best experts on this subject based on the ideXlab platform.

  • A study on laser drilling of thin steel sheet in air and underwater
    Journal of Applied Physics, 2010
    Co-Authors: Ashish Kumar Nath, Dulari Hansdah, A. Roy Choudhury
    Abstract:

    In laser drilling of a thin stainless steel sheet in air with Nd:YAG laser pulses of 0.5–1 ms durations it was observed that the 0.5 ms duration laser pulse was more effective in drilling a through-hole than the relatively longer laser pulses with proportionately more energy. Further, laser drilling could be readily done when the sheet was placed at the focal point of the lens and below it but not above the focal point. On the other hand, the underwater laser drilling could be done when the sheet was placed above the focal point. An attempt has been made to explain these experimental observations considering various processes involved in laser drilling in air and underwater. While the recoil pressure of the vapor and plasma played an important role in laser drilling in air; the radial gradient of recoil pressure of evaporation, the Marangoni Force induced by the surface tension gradient in melt pool and the cavitation effect of bubble collapse were believed to be responsible for the material removal in un...

  • A study on laser drilling of thin steel sheet in air and underwater
    Journal of Applied Physics, 2010
    Co-Authors: Ashish Kumar Nath, Dulari Hansdah, Subhransu Roy, A. Roy Choudhury
    Abstract:

    In laser drilling of a thin stainless steel sheet in air with Nd:YAG laser pulses of 0.5–1 ms durations it was observed that the 0.5 ms duration laser pulse was more effective in drilling a through-hole than the relatively longer laser pulses with proportionately more energy. Further, laser drilling could be readily done when the sheet was placed at the focal point of the lens and below it but not above the focal point. On the other hand, the underwater laser drilling could be done when the sheet was placed above the focal point. An attempt has been made to explain these experimental observations considering various processes involved in laser drilling in air and underwater. While the recoil pressure of the vapor and plasma played an important role in laser drilling in air; the radial gradient of recoil pressure of evaporation, the Marangoni Force induced by the surface tension gradient in melt pool and the cavitation effect of bubble collapse were believed to be responsible for the material removal in underwater drilling process.