help with fine/marine!

ellen lee · March 5, 2013, 11:08

I am using fine/marine with a planing hull, and the results are not very accurate,I am wondering is it because the froud number is over 3 or still problems with the meshing?

Rombzh · March 10, 2013, 09:45

You mean the predicted drag is off ? You might want to increase the y+ value, and already prescribe your final trim value in Hexpress.

ellen lee · March 12, 2013, 10:59

you mean fix the trim? but what if i don‘t know the final trim？

Rombzh · March 12, 2013, 12:05

Well you could use the trim value you got with your first run, even if forces were off, rotate your geometry in Hexpress and build the mesh.
You can also predict your final trim value with Savitsky's formulae.

lava12005 · June 16, 2013, 12:36

have you make sure there is no air entrapment below?
This I found to reduce the viscous drag significantly.
Check your mesh resolution on the transom as well, it needs to be fine enough so that the water separate from the hull nicely.

March 5, 2013, 11:08	help with fine/marine!	#1
ellen lee New Member Join Date: Mar 2012 Posts: 3 Rep Power: 14	I am using fine/marine with a planing hull, and the results are not very accurate,I am wondering is it because the froud number is over 3 or still problems with the meshing?

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March 10, 2013, 09:45		#2
Rombzh Member Romain Join Date: May 2009 Posts: 40 Rep Power: 17	You mean the predicted drag is off ? You might want to increase the y+ value, and already prescribe your final trim value in Hexpress.

March 12, 2013, 10:59		#3
ellen lee New Member Join Date: Mar 2012 Posts: 3 Rep Power: 14	you mean fix the trim? but what if i don‘t know the final trim？

March 12, 2013, 12:05		#4
Rombzh Member Romain Join Date: May 2009 Posts: 40 Rep Power: 17	Well you could use the trim value you got with your first run, even if forces were off, rotate your geometry in Hexpress and build the mesh. You can also predict your final trim value with Savitsky's formulae.

June 16, 2013, 12:36		#5
lava12005 Senior Member KHB Join Date: Aug 2010 Location: Singapore Posts: 118 Rep Power: 16	have you make sure there is no air entrapment below? This I found to reduce the viscous drag significantly. Check your mesh resolution on the transom as well, it needs to be fine enough so that the water separate from the hull nicely.