Numerical simulation of in-flight transportation in spray forming process

This thesis reports the research and development work on the computational modeling of aluminum spray forming processes. Spray forming is an innovative and very promising near-net shape metal casting method. The objective of this research is to develop numerical and theoretical tools needed in the simulation of flow dynamics and transportation phenomena of atomized liquid metal droplets flying in a gaseous environment during spray forming process.; The numerical procedure developed in this study features a fully interacting combination of Eulerian gas flow and Lagrangian droplet calculations in a three-dimensional body-fitted curvilinear grid system. The gas phase fluid flow is solved by using a pressure based control volume method. Flow turbulence is modeled through a two-equation k-□ model. The pressure-velocity coupling is formulated based on an operator-splitting technique (PISO).; The droplet phase is described in the Lagrangian reference systems, which allows properties to be statistically assigned for each individual droplet. A simplified Basset-Boussinesq-Oseen equation is solved to determine the droplet trajectories. Aluminum droplet solidification is modeled as a five-stage evolution process involving undercooling and recalescence. Special attention is given to physical modeling of spray impact on the substrate.; The interactions between gas and droplet phases are modeled through special source terms in the momentum and energy equations. The droplet gas momentum exchange is treated implicitly in the gas momentum equation through the splitting of the momentum interaction source term.; Several benchmark cases have been studied using the present computational procedure. Computational results matched well with measured results. The numerical procedure was then applied to the simulation of a pilot spray chamber at ALCOA. Statistical results obtained from the computation revealed important process information such as droplet distribution, velocity, temperature, solidification fraction, over-spray ratio, and deposition shape. Further investigation in the formation of deposition profiles also revealed that the gas flow pattern has significant influence on the deposition shape. Computed results showed favorable agreement with available experimental data.