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runtime error after succ. compilation + vector component division

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Old   May 22, 2011, 10:12
Default runtime error after succ. compilation + vector component division
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I have a problem in running after successfully compiling the modified rhoCentralFoam code.

volVectorField rhoU_dummy = rhoU_old;
:
:///////////
:
:
volScalarField q_2 = ( rhoU.component(vector::X) - rhoU_dummy.component(vector::X) ) / rhoU_dummy.component(vector::X) );

compiles well. But when it runs immediately shows "floating point exception" error.
The denominator going zero may be one of the reason. I tried even tried adding 1e-06 to it. It compiles well but throws away the same error during run time.

may be my vector component division goes wrong?

Can anyone help me please : )

Last edited by ramhari; May 22, 2011 at 14:08. Reason: I corrected the typo
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Old   May 25, 2011, 11:08
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You could try using the stabilise function on the denominator. Also, try adding log lines just prior to the equation, so you can see what values are going into it.
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Old   May 26, 2011, 01:18
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The velocity vector is initially set zero. I think by adding some 1e-06 to it before division should not show any problem. The floating point exception error shows at the
second iteration itself.
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Old   May 26, 2011, 08:37
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The stabilize function will add a small amount to the number if it is close to zero.
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Old   May 28, 2011, 15:53
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Dear marupio,

I am sorry that i m not getting clearly of what u mean by stabilise function. Can u pls post something of that sort!
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Old   May 28, 2011, 16:01
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Sorry, the function is stabilise(scalar value, scalar smallAmount).

I was wrong - it doesn't check if it is close to zero, it always adds the smallAmount. But, it will add it in the right direction (positive or negative).

Here's how you'd use it:

Code:
volScalarField q_2 = ( rhoU.component(vector::X) - rhoU_dummy.component(vector::X) ) / stabilise(rhoU_dummy.component(vector::X), SMALL) );
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Old   May 30, 2011, 06:40
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Thanks marupio,
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division, exception, floating, point, vector

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