Distinct influences of turbulence in momentum, heat and mass transfers during melt pool convection in a typical laser surface alloying process

¹ Department of Engineering, University of Liverpool, Brownlow Hill, Liverpool, L69 3GH, UK
² Department of Mechanical Engineering, Indian Institute of Technology, Kharagpur – 721302, India

Corresponding author: suman@mech.iitkgp.ernet.in

Received: 8 August 2005
Revised: 24 February 2006
Accepted: 29 May 2006
Published online: 5 September 2006

Abstract

The effects of turbulence on momentum, heat and solutal transport in a typical high power laser surface alloying process are numerically investigated. The turbulent transport is accounted for by employing a standard high Reynolds number k − ε model, suitably modified to take into account a dynamic evolution of the phase changing interfaces. Phase transitions are handled by using a modified enthalpy porosity technique. Diffusive effects associated with turbulence are found to significantly affect the momentum and solutal transport in the molten pool. On the other hand, enhancements in thermal diffusion on account of turbulence turn out to be rather marginal, with the molecular and eddy thermal diffusivities approximately of the same order. The generation and dissipation rates of turbulent kinetic energy are shown to be in local equilibrium. Based on this inference, a scaling analysis is also performed, which provides order of magnitude estimates of melt pool penetration, mean surface velocity, and temperature/concentration scales. The above estimations are found to be in good agreement with numerical simulation results, in an order of magnitude sense.