air under hull

laurent98 · May 2, 2012, 17:38

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, 22:07

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, 20:42

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, 09:27

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!

May 2, 2012, 17:38	air under hull	#1
laurent98 New Member laurentL Join Date: Oct 2011 Location: new caledonia Posts: 25 Rep Power: 3	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

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May 2, 2012, 18:38		#2
laurent98 New Member laurentL Join Date: Oct 2011 Location: new caledonia Posts: 25 Rep Power: 3	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!!!

February 4, 2013, 22:07		#3
laurent98 New Member laurentL Join Date: Oct 2011 Location: new caledonia Posts: 25 Rep Power: 3	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

February 13, 2013, 20:42		#4
lava12005 Member KHB Join Date: Aug 2010 Location: Singapore Posts: 73 Rep Power: 4	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?

February 18, 2013, 09:27		#5
laurent98 New Member laurentL Join Date: Oct 2011 Location: new caledonia Posts: 25 Rep Power: 3	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!