Simplified 2D thermo-mechanical modelling of splat formation in plasma spraying processes

Paper presented at the 6th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 30 June - 2 July, 2008.The particles projected by arc plasma are generally of micrometric size (ranging in general between 10 and 100 μm) in conventional projection and their impact velocity ranges from 50 to 350 m/s. characteristic times for the formation of a splate are very short: less than 5 μs for the duration of spreading of the particle melted with a solidification which can start before the end of the spreading stage and continues in general between 0.8 and 10 μs after the impact.This work is devoted to studying numerically this complex coupling. The model is firstly validated in comparison with available results of particles spreading (large size and low impact velocity < 1 m/s).vk201

Study of a double-layered sphere melting subjected to conditions of not uniform heat flux

Paper presented at the 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 1-4 July, 2007.This paper deals with solid/liquid transition in a double-layered micrometric composite spherical particle metal/ceramic injected into a high temperature plasma jet of argon-hydrogen. The analysis focuses on tracking the particle following its trajectory in order to consider its thermal heat history. The heat transfer equation is formulated by using the enthalpy method and its discretization is carried out by a technique of second order finite volumes in time and space. The obtained results show the significant effect of the geometrical parameters, the phase change and the coupled heat transfer.cs201

Numerical simulation of convective flows occuring during AL-4.1WT%CU solidification

Paper presented at the 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 1-4 July, 2007.This study presents a numerical simulation of the convective laminar flow, driven by combined thermo-solutally buoyancy forces, under a uniform horizontally applied magnetic field, held during the solidification of a molten alloy Al- 4.1wt%Cu filled in a rectangular cavity. The continuum model, of Bennon and Incropera [1], was used in the development of the mathematical model, representing the solidification phenomena. Following this model, the alloy solidification process is governed by continuity, Navier-Stokes, energy, species and electrical potential conservation equations. Here solved by using finite volume method. The effect intensity of the magnetic field on convective flow has been investigated. The governing equations are firstly non-dimensionalized and are approximated by using a finite volume method.cs201

Construction and characterisation of a BAC library for genome analysis of the allotetraploid coffee species (Coffea arabica L.)

www.springer-ny.comInternational audienceIn order to promote genome research on coffee trees, one of the most important tropical crops, a bacterial artificial chromosome (BAC) library of the coffee allotetraploid species, Coffea arabica, was constructed. The variety IAPAR 59, which is widely distributed in Latin America and exhibits a fair level of resistance to several pathogens, was chosen. High-efficiency BAC cloning of the high molecular weight genomic DNA partially digested by HindIII was achieved. In total, the library contains 88,813 clones with an average insert size of 130 kb, and represents approximately eight C. arabica dihaploid genome equivalents. One original feature of this library is that it can be divided into four sublibraries with mean insert sizes of 96, 130, 183 and 210 kb. Characterisation of the library showed that less than 4.5% of the clones contained organelle DNA. Furthermore, this library is representative and shows good genome coverage, as established by hybridisation screening of high-density filters using a number of nuclear probes distributed across the allotetraploid genome. This Arabica BAC library, the first large-insert DNA library so far constructed for the genus Coffea, is well-suited for many applications in genome research, including physical mapping, map-based cloning, functional and comparative genomics as well as polyploid genome analyses

Lattice Boltzmann Computation of Plasma Jet Behaviors: part II Argon-Nitrogen Mixture

Abstract – In this paper an innovative computational approach, namely the Lattice Boltzmann Method (LBM), is used for simulating and modeling plasma jet behaviors. Plasma jets are a high temperature flows, then all physical parameters are temperature dependent. This work aims to address the issue of simulating plasma-jet from the point of view of extending the applications to simulating flows with temperature-dependent diffusion parameters (viscosity and diffusivity), focusing on the phenomena occurring in plasma-jet flow for a mixture of plasma gases, N2-Ar62.5 % vol. Argon and Nitrogen are two gases of the most ones used in plasma spraying. The mixture is used when looking for some jet properties. We limit our effort to take out the dynamic and thermal characteristics of this complex flow using the lattice Boltzmann equation. An important section focuses mainly on the validation of our results with compute jet dynamics software such as GENMIX and Jets&amp;Poudres developed in laboratory SPCTS in several updated edition. These codes established for many turbulence models (k-epsilon, k-omega, Prandtl&apos;s models…) are helpful numerical keys for understanding the physics of plasma jets and plasma spraying. Our numerical results based on the centerline temperature and velocity profiles, its distributions over the computational domain, the gaussian radial profiles and the effects of inlet quantities are analyzed. The quality of the results shows a great efficiency for the lattice Boltzmann method