air under hull

laurent98 · May 2, 2012, 18:38

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, 19:38

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!

May 2, 2012, 18:38	air under hull	#1
laurent98 Member laurentL Join Date: Oct 2011 Location: new caledonia Posts: 73 Rep Power: 15	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

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Simulation of air flow in a chamber	Issa	CFX	3	November 23, 2009 18:16
Chemical Equilibrium Composition of Air and other Species	enigma	Main CFD Forum	0	November 11, 2009 20:08
Lumped air mass	Koranten	FLUENT	0	August 26, 2009 04:09
air bubble is disappear increasing time using vof	xujjun	CFX	9	June 9, 2009 08:59
Help!!!problems in air jet into water bath	kim	FLUENT	4	June 9, 2003 08:04

May 2, 2012, 19:38		#2
laurent98 Member laurentL Join Date: Oct 2011 Location: new caledonia Posts: 73 Rep Power: 15	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, 23:07		#3
laurent98 Member laurentL Join Date: Oct 2011 Location: new caledonia Posts: 73 Rep Power: 15	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, 21:42		#4
lava12005 Senior Member KHB Join Date: Aug 2010 Location: Singapore Posts: 118 Rep Power: 16	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, 10:27		#5
laurent98 Member laurentL Join Date: Oct 2011 Location: new caledonia Posts: 73 Rep Power: 15	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!