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 pyxbird March 21, 2013 21:12

f-packing

Dear all,
Hi, sometimes flow3d just recommends me to ruduce the f-packing coefficient(cfpk) by factor of 10, and its default value is 1, that means I should change it into 0.1.
I want to ask, does the value of this coefficient make sense significantly?
What's the difference between 1 and 0.1, will it influence the outcome of the simulation greatly? I am still confused after reading the mannal given by the software.

 dmilano March 25, 2013 10:13

The f-packing algorithm is intended to prevent voids from opening inside of continuous fluid regions due to roundoff errors. It is a numerical adjustment, so the coefficient has little physical meaning. Adjusting the coefficient controls the strength of the adjustment and usually does not have a significant impact on the results. There is a caveat here: values that are too small will prevent the algorithm from operating as intended, while values that are too large may influence the solution. The latter scenario is a very rare case and is easily avoidable if you do not increase the f-packing coefficient above the default value of one.

 pyxbird March 25, 2013 20:11

Quote:
 Originally Posted by dmilano (Post 416240) The f-packing algorithm is intended to prevent voids from opening inside of continuous fluid regions due to roundoff errors. It is a numerical adjustment, so the coefficient has little physical meaning. Adjusting the coefficient controls the strength of the adjustment and usually does not have a significant impact on the results. There is a caveat here: values that are too small will prevent the algorithm from operating as intended, while values that are too large may influence the solution. The latter scenario is a very rare case and is easily avoidable if you do not increase the f-packing coefficient above the default value of one.
Thank you！

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