CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   FLOW-3D (http://www.cfd-online.com/Forums/flow-3d/)
-   -   f-packing (http://www.cfd-online.com/Forums/flow-3d/115021-f-packing.html)

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!


All times are GMT -4. The time now is 06:16.