Empirical regression equations permit the calculation of liquid phase epitaxial (LPE) film properties from film growth parameters. Numerical differentiation of these equations facilitates examination of the sensitivities of film properties to fluctuations in growth conditions and the development of depletion-compensating growth strategies. Regression equations for nominal 3-ILm bubble size CaGe and Ga films have been generated and used for quantitative comparisons of the growth behavior of the two systems. A real time feedback control scheme has been applied to the Ga system resulting in 70 percent of the as-grown films falling within ± 1 percent of the target collapse field.
A numerical model that enables the simulation of polydispersed spray behavior while allowing the resolution of droplet-scale features is described. This Lagrangian model is based on a sectional approach and captures the effect of polydispersity, droplet initial speed and direction. It is designed for flexibility in that it can be used for a variety of droplet-based processes. The model performance is illustrated using two basic configurations: spray combustion and water mist fire suppression. The spray combustion case shows how the droplet-scale resolution can be critical since phase equilibrium is controlled by droplet surface temperature, which cannot be adequately captured using a lump-parameter model. The water mist case allows a demonstration of the basic features of the spray model such as the ability to characterize the ability of smaller droplets to get close enough to a fire or a hot surface.
The work presented here aims at characterizing the dynamics of water mist during fire suppression events in cluttered spaces. To this end, a numerical model for a polydispersed water-mist is used. A sectional approach is used to describe the mist behavior. The distributions of the parameters characterizing the mist (size, speed, and direction at injection) are discretized in classes, and they are chosen using a Monte Carlo method. The fate of the droplets in each class is determined by calculating the history of a representative droplet for each class using a Lagrangian approach. The dynamics of the representative droplets and their heat and mass transfer histories are tracked. An extended-film model is used to evaluate droplet evaporation. This mist model interacts in a one-way coupled manner with a pre-calculated flow field around hot obstacles.
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