CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   NUMECA (http://www.cfd-online.com/Forums/numeca/)
-   -   air under hull (http://www.cfd-online.com/Forums/numeca/101388-air-under-hull.html)

laurent98 May 2, 2012 17:38

air under hull
 
Hi,
i am a new NUMECA user. in a simulation of a high speed boat, it look like air going under the hull. what is the influences parameters to limite this effect.
thank you by advance for answers LL

laurent98 May 2, 2012 18:38

sorry for disturbing,
the answer is in the documentation...
increase orthogonality, longer acceleration, CiStreakCorrection_YES; uwCiCorrection_YES
better question will be for a next time!!!

laurent98 February 4, 2013 23:07

my actual problem is that coeficents, make the solution unstable... and so the results non available...
is there another solutions???
thank you for answering
LL

lava12005 February 13, 2013 21:42

Hi, been trying NUMECA for a while for high speed boat simulation also.
As you said I did notice that the uwCiCorrection_YES makes the solution more unstable for me. The CiStreakCorrection_Yes is better though..

Btw, are you running the full unsteady or the quasi-static analysis?
What is your Fn (by wetted length) that you are simulating?
What is the y+ of your hull? If it is too small, try to increase it, I suspect the air entrapment is due to AR of the cells near the interface is too big and/or the mesh is not refined enough..
Increasing orthogonality / refining the mesh helps but CPU cost will increase a lot!

Anyone has a suggestion?

laurent98 February 18, 2013 10:27

Hi,
i found a solution, you must adjust the uwCorretionCoef_ in the line just under uwCiCorrection_YES!
for my case 0.3 was not enough but with 0.8 i had some good results. look at the pressure repartition on hull with this coef, it much better!


All times are GMT -4. The time now is 19:06.