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Tarasankar Debroy - One of the best experts on this subject based on the ideXlab platform.
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Heat Transfer and Fluid Flow during Gas-Metal-Arc Fillet Welding for Various Joint Configurations and Welding Positions
Metallurgical and Materials Transactions A, 2007Co-Authors: A. Kumar, Tarasankar DebroyAbstract:Gas-metal-arc (GMA) fillet welding is one of the most commonly used welding processes in the industry. This welding process is characterized by the complex joint geometry, a deformable weld pool Surface, and the addition of hot metal droplets. In this work, a three-dimensional numerical heat-transfer and fluid-flow model is developed to capture the effects of the tilt angle of the fillet joint and the welding positions, i.e. , V, L, and other configurations on the temperature Profiles, velocity fields, weld pool shape, weld pool Free Surface Profile, thermal cycles, and cooling rates during GMA welding in spray mode. The governing equations of conservation of mass, momentum, and energy are solved using a boundary fitted curvilinear coordinate system. The weld pool Free Surface deformation is calculated by minimizing the total Surface energy. A dimensional analysis is performed to understand the importance of heat transfer by conduction and convection and the role of various driving forces on convection in the liquid weld pool. The computed shape and size of the fusion zone, finger penetration characteristic of the GMA welds, and the solidified Free Surface Profile are in fair agreement with the corresponding experimental results. The calculated cooling rates are also in good agreement with independent experimental data. The results reported here indicate a significant promise for understanding the effect of joint orientations and welding positions on weld pool shape, size, and the cooling rates based on fundamental principles of transport phenomena.
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liquid metal expulsion during laser spot welding of 304 stainless steel
Journal of Physics D, 2006Co-Authors: J T Norris, P W Fuerschbach, Tarasankar DebroyAbstract:During laser spot welding of many metals and alloys, the peak temperatures on the weld pool Surface are very high and often exceed the boiling points of materials. In such situations, the equilibrium pressure on the weld pool Surface is higher than the atmospheric pressure and the escaping vapour exerts a large recoil force on the weld pool Surface. As a consequence, the molten metal may be expelled from the weld pool Surface. The liquid metal expulsion has been examined both experimentally and theoretically for the laser spot welding of 304 stainless steel. The ejected metal droplets were collected on the inner Surface of an open ended quartz tube which was mounted perpendicular to the sample Surface and co-axial with the laser beam. The size range of the ejected particles was determined by examining the interior Surface of the tube after the experiments. The temperature distribution, Free Surface Profile of the weld pool and the initiation time for liquid metal expulsion were computed based on a three-dimensional transient heat transfer and fluid flow model. By comparing the vapour recoil force with the Surface tension force at the periphery of the liquid pool, the model predicted whether liquid metal expulsion would take place under different welding conditions. Expulsion of the weld metal was also correlated with the depression of the liquid metal in the middle of the weld pool due to the recoil force of the vapourized material. Higher laser power density and longer pulse duration significantly increased liquid metal expulsion during spot welding.
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guaranteed fillet weld geometry from heat transfer model and multivariable optimization
International Journal of Heat and Mass Transfer, 2004Co-Authors: A. Kumar, Tarasankar DebroyAbstract:Abstract Numerical heat transfer models of gas metal arc (GMA) fillet welding do not always predict correct temperature fields and fusion zone geometry. The inaccuracy results, to a large extent, due to the difficulty in correctly specifying several input parameters such as arc efficiency from scientific principles. In order to address this problem, a heat transfer model is combined with an optimization algorithm to determine several uncertain welding parameters from a limited volume of experimental data. The resulting smart model guarantees optimized prediction of weld pool penetration, throat and leg-length within the framework of phenomenological laws. A boundary fitted coordinate system was used to account for the complex fusion zone shape. The weld pool Surface Profile was calculated by minimizing the total Surface energy. Apart from the direct transport of heat from the welding arc, heat transfer from the metal droplets was modeled considering a volumetric heat source. The Levenberg–Marquardt and two versions of conjugate gradient method were used to calculate the optimized values of unknown parameters. An appropriate objective function that represented the difference between the calculated and experimental values of the penetration, throat and leg-length was minimized. The calculated shape and size of the fusion zone, finger penetration characteristic of the GMA welds and the solidified Free Surface Profile were in fair agreement with the experimental results for various welding conditions.
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heat and fluid flow in complex joints during gas metal arc welding part i numerical model of fillet welding
Journal of Applied Physics, 2004Co-Authors: Wei Zhang, Cheolhee Kim, Tarasankar DebroyAbstract:Gas metal arc (GMA) fillet welding is one of the most important processes for metal joining because of its high productivity and amiability to automation. This welding process is characterized by the complicated V-shaped joint geometry, a deformable weld pool Surface, and the additions of hot metal droplets. In the present work, a three-dimensional numerical heat transfer and fluid flow model was developed to examine the temperature Profiles, velocity fields, weld pool shape and size, and the nature of the solidified weld bead geometry during GMA fillet welding. The model solved the equations of conservation of mass, momentum, and energy using a boundary fitted curvilinear coordinate system. Apart from the direct transport of heat from the welding arc, additional heat from the metal droplets was modeled considering a volumetric heat source. The deformation of the weld pool Surface was calculated by minimizing the total Surface energy. Part I of this article is focused on the details of the numerical model such as coordinate transformation and calculation of volumetric heat source and Free Surface Profile. An application of the model to GMA fillet welding of mild steel is described in an accompanying article (W. Zhang, C.-H. Kim and T. DebRoy, J. Appl Phys. 95, 5220 (2004)).
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modeling of temperature field and solidified Surface Profile during gas metal arc fillet welding
Journal of Applied Physics, 2003Co-Authors: Cheolhee Kim, Wei Zhang, Tarasankar DebroyAbstract:The temperature Profiles, weld pool shape and size, and the nature of the solidified weld pool reinforcement Surface during gas–metal arc (GMA) welding of fillet joints were studied using a three-dimensional numerical heat transfer model. The model solves the energy conservation equation using a boundary fitted coordinate system. The weld pool Surface Profile was calculated by minimizing the total Surface energy. Apart from the direct transport of heat from the welding arc, additional heat from the metal droplets was modeled considering a volumetric heat source. The calculated shape and size of the fusion zone, finger penetration characteristic of the GMA welds, and the solidified Free Surface Profile were in fair agreement with the experimental results for various welding conditions. In particular, the computed values of important geometric parameters of fillet welds, i.e., the leg length, the penetration depth, and the actual throat, agreed well with those measured experimentally for various heat inputs...
Hubert Chanson - One of the best experts on this subject based on the ideXlab platform.
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Air-water interaction and characteristics in breaking bores
International Journal of Multiphase Flow, 2019Co-Authors: Xinqian Leng, Hubert ChansonAbstract:Abstract A tidal bore is an unsteady rapidly-varied open channel flow characterised by a rise in water Surface elevation in estuarine zones, under spring tidal conditions. After formation, the bore is traditionally analysed as a hydraulic jump in translation and its leading edge is characterised by a breaking roller for Froude number Fr1 > 1.3–1.5. The roller is a key flow feature characterised by intense turbulence and air bubble entrainment. Detailed unsteady air-water flow measurements were conducted in a breaking bore propagating in a large-size channel, using an array of three dual-tip phase detection probes and photographic camera. The data showed a relatively steep roller, with a short and dynamic bubbly flow region. Air entrainment took place in the form of air entrapment at the roller toe, air-water exchange across the roller 'Free-Surface', spray and splashing with dynamic water drop ejection and re-attachment, roll up and roll down of water 'tongues' engulfing air pockets. The roller Free-Surface Profile and characteristics were comparable to observations in stationary hydraulic jumps and steady breaker, for similar flow conditions. Within the roller, the amount of entrained air was quantitatively small for Froude number Fr1 = 2.2. The number of air bubbles was limited, with between 5 and 20 bubbles per phase-detection probe sensor detected at each vertical elevation. The entrained air bubble chord lengths spanned over several orders of magnitude, with a large proportion of clustered bubbles. Overall, the study highlighted the three-dimensional nature of the air-water roller motion and strong evidence of the in-homogeneity of the turbulent air-water mixture.
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a numerical study of open channel flow hydrodynamics and turbulence of the tidal bore and dam break flows
2008Co-Authors: Shoichi Furuyama, Hubert ChansonAbstract:A numerical model was developed based upon the Cubic-Interpolated Pseudo-particle (CIP) Combined Unified Procedure (CIP-CUP or C-CUP) method equipped with a Large Eddy Simulation (LES) model and a re-initialisation method. The model was validated and applied to the laminar dam-break flow problem, the turbulent dam-break flow problem and the tidal bore flow with a weak breaking front. In the laminar dam break flow problem the model resolved the Free Surface Profiles, and the flow calculations were in good agreement with the experiment studies of Martin and Moyce (1952) and the experimental and numerical test of Koshizuka et al. (1995) and Koshizuka and Oka (1996). In the turbulent dam break flow problem, the model included a LES turbulence model and it was applied to a dam break wave in a relatively long channel. The shape of the leading edge was compared with the experimental studies, e.g. Dressler (1952, 1954); Cavaille (1965) and theoretical studies, e.g. Chanson (2005, 2006). In the tidal bore flow with a weak breaking front, the model equipped with a LES turbulence model reproduced accurately the large deformation of the Free Surface immediately after gate closure and the bore generation. The Free-Surface Profile and surge front celerity data were in good agreement with the experimental data of Koch and Chanson (2005). At a fixed sampling location, the numerical results showed the existence of some short-lived flow reversal next to the bed immediately after the bore front passage. This flow feature was documented by Koch and Chanson (2005) and Chanson (2007). By applying the method to these complex flows, it was shown that the numerical technique was effective for the analysis of various flows in civil engineering applications.
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tsunami surges on dry coastal plains application of dam break wave equations
Coastal Engineering Journal, 2006Co-Authors: Hubert ChansonAbstract:Surge waves resulting from dam breaks have been responsible for numerous losses of life. A related situation is the tsunami surges advancing on dry coastal plains. Herein a simple dam break wave solution is presented. The results yield some simple expressions of the instantaneous Free-Surface Profile and flow depths that compare well with well-known dam break wave data. The results are applied to tsunami surges on dry coastal plains and compared with some data set. The present development offers simple analytical expressions that compare well with both experimental data and more advanced theoretical solutions, and that are further well-suited for pedagogical purposes, computational model validation, and accurate real-time predictions of tsunami surges.
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analytical solution of dam break wave with flow resistance application to tsunami surges
31st IAHR Congress 2005: Water Engineering for the Future Choices and Challenges, 2005Co-Authors: Hubert ChansonAbstract:Surge waves resulting from dam breaks have been responsible for numerous losses of life. Related situations include flash floods, debris flow surges, surging waves in the swash zone, and tsunami surges on dry coastal plains. Herein the dam break wave flow is analysed as a wave tip region where flow resistance is dominant, followed by an ideal-fluid flow region where inertial effects and gravity effects are dominant. The analytical development yields an explicit expression of the instantaneous Free-Surface Profile and flow properties that compare well with well-known experimental data. Results are then applied to tsunami surges on dry coastal plains, and compared with some data set. The present development offers simple analytical expressions that compare well with both experimental data and more advanced theoretical solutions, and that are further well-suited for pedagogical purposes as well as computational model validation.
Angela Ferrari - One of the best experts on this subject based on the ideXlab platform.
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sph simulation of Free Surface flow over a sharp crested weir
Advances in Water Resources, 2010Co-Authors: Angela FerrariAbstract:Abstract In this paper the numerical simulation of a Free Surface flow over a sharp-crested weir is presented. Since in this case the usual shallow water assumptions are not satisfied, we propose to solve the problem using the full weakly compressible Navier–Stokes equations with the Tait equation of state for water. The numerical method used consists of the new meshless Smooth Particle Hydrodynamics (SPH) formulation proposed by Ferrari et al. (2009) [8] , that accurately tracks the Free Surface Profile and provides monotone pressure fields. Thus, the unsteady evolution of the complex moving material interface (Free Surface) can been properly solved. The simulations involving about half a million of fluid particles have been run in parallel on two of the most powerful High Performance Computing (HPC) facilities in Europe. The validation of the results has been carried out analysing the pressure field and comparing the Free Surface Profiles obtained with the SPH scheme with experimental measurements available in literature [18] . A very good quantitative agreement has been obtained.
Cheolhee Kim - One of the best experts on this subject based on the ideXlab platform.
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heat and fluid flow in complex joints during gas metal arc welding part i numerical model of fillet welding
Journal of Applied Physics, 2004Co-Authors: Wei Zhang, Cheolhee Kim, Tarasankar DebroyAbstract:Gas metal arc (GMA) fillet welding is one of the most important processes for metal joining because of its high productivity and amiability to automation. This welding process is characterized by the complicated V-shaped joint geometry, a deformable weld pool Surface, and the additions of hot metal droplets. In the present work, a three-dimensional numerical heat transfer and fluid flow model was developed to examine the temperature Profiles, velocity fields, weld pool shape and size, and the nature of the solidified weld bead geometry during GMA fillet welding. The model solved the equations of conservation of mass, momentum, and energy using a boundary fitted curvilinear coordinate system. Apart from the direct transport of heat from the welding arc, additional heat from the metal droplets was modeled considering a volumetric heat source. The deformation of the weld pool Surface was calculated by minimizing the total Surface energy. Part I of this article is focused on the details of the numerical model such as coordinate transformation and calculation of volumetric heat source and Free Surface Profile. An application of the model to GMA fillet welding of mild steel is described in an accompanying article (W. Zhang, C.-H. Kim and T. DebRoy, J. Appl Phys. 95, 5220 (2004)).
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modeling of temperature field and solidified Surface Profile during gas metal arc fillet welding
Journal of Applied Physics, 2003Co-Authors: Cheolhee Kim, Wei Zhang, Tarasankar DebroyAbstract:The temperature Profiles, weld pool shape and size, and the nature of the solidified weld pool reinforcement Surface during gas–metal arc (GMA) welding of fillet joints were studied using a three-dimensional numerical heat transfer model. The model solves the energy conservation equation using a boundary fitted coordinate system. The weld pool Surface Profile was calculated by minimizing the total Surface energy. Apart from the direct transport of heat from the welding arc, additional heat from the metal droplets was modeled considering a volumetric heat source. The calculated shape and size of the fusion zone, finger penetration characteristic of the GMA welds, and the solidified Free Surface Profile were in fair agreement with the experimental results for various welding conditions. In particular, the computed values of important geometric parameters of fillet welds, i.e., the leg length, the penetration depth, and the actual throat, agreed well with those measured experimentally for various heat inputs...
Wei Zhang - One of the best experts on this subject based on the ideXlab platform.
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heat and fluid flow in complex joints during gas metal arc welding part i numerical model of fillet welding
Journal of Applied Physics, 2004Co-Authors: Wei Zhang, Cheolhee Kim, Tarasankar DebroyAbstract:Gas metal arc (GMA) fillet welding is one of the most important processes for metal joining because of its high productivity and amiability to automation. This welding process is characterized by the complicated V-shaped joint geometry, a deformable weld pool Surface, and the additions of hot metal droplets. In the present work, a three-dimensional numerical heat transfer and fluid flow model was developed to examine the temperature Profiles, velocity fields, weld pool shape and size, and the nature of the solidified weld bead geometry during GMA fillet welding. The model solved the equations of conservation of mass, momentum, and energy using a boundary fitted curvilinear coordinate system. Apart from the direct transport of heat from the welding arc, additional heat from the metal droplets was modeled considering a volumetric heat source. The deformation of the weld pool Surface was calculated by minimizing the total Surface energy. Part I of this article is focused on the details of the numerical model such as coordinate transformation and calculation of volumetric heat source and Free Surface Profile. An application of the model to GMA fillet welding of mild steel is described in an accompanying article (W. Zhang, C.-H. Kim and T. DebRoy, J. Appl Phys. 95, 5220 (2004)).
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modeling of temperature field and solidified Surface Profile during gas metal arc fillet welding
Journal of Applied Physics, 2003Co-Authors: Cheolhee Kim, Wei Zhang, Tarasankar DebroyAbstract:The temperature Profiles, weld pool shape and size, and the nature of the solidified weld pool reinforcement Surface during gas–metal arc (GMA) welding of fillet joints were studied using a three-dimensional numerical heat transfer model. The model solves the energy conservation equation using a boundary fitted coordinate system. The weld pool Surface Profile was calculated by minimizing the total Surface energy. Apart from the direct transport of heat from the welding arc, additional heat from the metal droplets was modeled considering a volumetric heat source. The calculated shape and size of the fusion zone, finger penetration characteristic of the GMA welds, and the solidified Free Surface Profile were in fair agreement with the experimental results for various welding conditions. In particular, the computed values of important geometric parameters of fillet welds, i.e., the leg length, the penetration depth, and the actual throat, agreed well with those measured experimentally for various heat inputs...
