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Topic: ? influence of temporal discretization
Replies: 1   Last Post: May 25, 2012 5:41 AM

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Cheng Cosine

Posts: 176
Registered: 7/14/08
? influence of temporal discretization
Posted: May 19, 2012 8:02 AM
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Suppose we have a diffusion eqn: dT/dt = a*div(grad(T))+Q in non-
dimensional form.

a ~ 1.0E-6

Q changes with time and space. The problem is 3D, z is the depth

The spatial form of Q is roughly a Gaussian function with equal
standard deviation (STD) in x and y

directions and a larger STD in z direction; all these 3 STDs are
small, i.e., the function is sharply

concentrated in a confimed spatial region.

The focus (or center) of Q moves raipdly in a target region. This
region is a circle, and the focus

of Q moves spirially from the center of the circle to its boundary. At
each (spatial) point, Q stays

only 0.1 sec, and then immediately moves to the next point. Q starts
from time 0 and stops at

300 sec.

Now, we want to observe the saptial temperature profile at 500 sec.
Can we discretize the time

using dt as 0.1 sec or should we use a dt even smaller? How do we
estimate the appropriate

value of dt?


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