Y+ problem

pipin · August 18, 2009, 05:33

Hello,

I've a problem with my mesh, i have Y+ > 1000 in a nozzle.
With the non equilibrium law (30<Y+<300) what do you think about the wall treatment in this condition?
thanks for reply

delfel · August 19, 2009, 23:34

Hi Pipin,

I believe you should refine your mesh in the areas with y+ over 300 -- the turbulence model assumes a "shape" of the velocity profile below the first grid point, which is why it is important to get it in the right location. My suggestion would be to check the y+ value using contours -> turbulence -> wall y+ in fluent and then refine your grid in gambit (or whichever preprocessor you're using). You can also use the adaption tools in fluent, but I generally don't like the changes they make and end up with convergence problems. That could be because I'm not using them properly, though.

Cheers,
-sean

alekpopob · August 20, 2009, 16:10

U must refine mesh at wall as your turbulence model.
It is very inportant, because viscousity calculation near wall seriously depends on wall grid condition.

chillyfeng · August 20, 2009, 20:59

you can also use the near-wall model in fluent if you want to get the accurate representation of the flow in the near-wall region.

August 18, 2009, 05:33	Y+ problem	#1
pipin New Member pipin Join Date: Apr 2009 Posts: 20 Rep Power: 17	Hello, I've a problem with my mesh, i have Y+ > 1000 in a nozzle. With the non equilibrium law (30<Y+<300) what do you think about the wall treatment in this condition? thanks for reply

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
UDF compiling problem	Wouter	Fluent UDF and Scheme Programming	6	June 6, 2012 04:43
Incoherent problem table in hollow-fiber spinning	Gianni	FLUENT	0	April 5, 2008 10:33
natural convection problem for a CHT problem	Se-Hee	CFX	2	June 10, 2007 06:29
Adiabatic and Rotating wall (Convection problem)	ParodDav	CFX	5	April 29, 2007 19:13
Is this problem well posed?	Thomas P. Abraham	Main CFD Forum	5	September 8, 1999 14:52

August 19, 2009, 23:34		#2
delfel New Member Sean Delfel Join Date: Aug 2009 Posts: 27 Rep Power: 16	Hi Pipin, I believe you should refine your mesh in the areas with y+ over 300 -- the turbulence model assumes a "shape" of the velocity profile below the first grid point, which is why it is important to get it in the right location. My suggestion would be to check the y+ value using contours -> turbulence -> wall y+ in fluent and then refine your grid in gambit (or whichever preprocessor you're using). You can also use the adaption tools in fluent, but I generally don't like the changes they make and end up with convergence problems. That could be because I'm not using them properly, though. Cheers, -sean

August 20, 2009, 16:10		#3
alekpopob New Member Join Date: Jul 2009 Posts: 4 Rep Power: 16	U must refine mesh at wall as your turbulence model. It is very inportant, because viscousity calculation near wall seriously depends on wall grid condition.

August 20, 2009, 20:59		#4
chillyfeng New Member feng Join Date: Aug 2009 Posts: 1 Rep Power: 0	you can also use the near-wall model in fluent if you want to get the accurate representation of the flow in the near-wall region.