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5.11 Convergence

Every change to the parameters driving this model causes changes to the details of the solution, including number of bubbles at any given timestep, when and where a specific bubble nucleates and how large it grows before it bursts, and so on. Although the details vary considerably, the rate at which the sample loses mass averaged over a time period large compared to a single timestep is relatively stable.

Convergence properties were measured for PMMA with drainage time before bursting of 10 ms. For a fixed number of elements, quadratic convergence was found in time. Convergence was not established in space. However, results fell into a narrow range of values for sufficiently resolved time and space variables. A timestep of 0.25 ms and division of the sample into 40 elements was found to be satisfactory in determining pyrolysis time to better than one percent.


Next: Results Up: Computational Approach Previous: Energy Equation