| Summary: | 碩士 === 國立成功大學 === 工程科學系 === 86 === ABSTRACTSolidification process plays an important role in
casting industry. There exists many solidification models. How
to choose a proper model, how to use the model correctly or how
to to diagnose a new model is really a problem.This paper is to
set up a method to anaylze solidification models. One
dimensional Stefan problem and two-dimensional Rathjen problem
are used to test the models. In the method, the node number and
Stefan number are fixed, and different time step sizes are
applied. The root-mean-square error, the maximum error, the CPU
time and the iteration number are used to judge whether a model
is good. In the paper, four example models are used to test the
method: (1) the specific heat method (2) the enthalpy method (3)
the source term method (4) the simple source term method.From
the computational results, the enthalpy method is the most
accurate, and the simple source method and the specific heat
method are the worst. However, for the CPU time, the specific
heat method and the simple source method take the least time,
and the enthalpy method takes the most. In the simple source
term method, the relationship between liquid fraction and
temperature is assumed to be linear. The relationships other
than linear are also considered in this study. They do not
affect the CPU time, but change the accuracy. It is indicated
that a fast and accurate method may be obtained by finding a
proper relationship between them.
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