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March 17, 2005, 05:11 |
How to set up transient BC?
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#1 |
Guest
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Hi,
I've a problem setting up the transient BC. What I wish to get is: 1-2 sec, function1(t) 2-4 sec, function2(t) 4-6 sec, function1(t) 6-8 sec, function2(t) ...... Anyone know how to implement this expression in CFX-Pre? Thanks, Sam |
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March 17, 2005, 09:10 |
Re: How to set up transient BC?
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#2 |
Guest
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Hi Sam,
Create expressions for each of your functions:function1 = ... function2 = ... ...Then create an expression that includes all the functions and multiplies each by a corresponding step function:allFunctions = function1*step((2 [s]-t)/1[s]) + function2*step((t-2 [s])/1[s])*step((4 [s]-t)/1[s]) + function3*step((t-4 [s])/1[s])*step((6 [s]-t)/1[s]) + function2*step((t-6 [s])/1[s])*step((8 [s]-t)/1[s]) + ...A step function takes a dimensionless argument (hence dividing by 1 [s]). If the argument is negative, it returns zero, positive returns 1 and if it is equal to zero, it returns 1/2. By combining your functions this way, you can turn them on and off as needed. Regards, Robin |
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March 17, 2005, 21:09 |
Thank you.
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#3 |
Guest
Posts: n/a
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Thanks, robin.
It works eventhough it's lengthy. I've to simulate over 40 sec & allfunction becomes a giant equation. |
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