Y+ upper bound

saisanthoshm88 · October 2, 2012, 17:15

In relation to the k - epsilon turbulence model I infer the following from the CFX documentation:

" Y+≥11.06 and the upper limit for y+ is a function of the device Reynolds number. For example, a large ship may have a Reynolds number of 10^9 and y+ can safely go to values much greater than 1000. For lower Reynolds numbers (for example, a small pump), the entire boundary layer might only extend to around y+ = 300. In this case, a fine near wall spacing is required to ensure a sufficient number of nodes in the boundary layer. "

Could some one please explain how to check if a particular Y+ is apt for a flow with a particular Reynolds number (or) is there any way to calculate the required Y+ before starting the simulation if the Reynolds number is known

ghorrocks · October 2, 2012, 19:00

Sensitivity study - the same answer for just about any adjustable parameter in CFD.

October 2, 2012, 17:15	Y+ upper bound	#1
saisanthoshm88 Senior Member --------- Join Date: Oct 2010 Posts: 303 Rep Power: 17	In relation to the k - epsilon turbulence model I infer the following from the CFX documentation: " Y+≥11.06 and the upper limit for y+ is a function of the device Reynolds number. For example, a large ship may have a Reynolds number of 10^9 and y+ can safely go to values much greater than 1000. For lower Reynolds numbers (for example, a small pump), the entire boundary layer might only extend to around y+ = 300. In this case, a fine near wall spacing is required to ensure a sufficient number of nodes in the boundary layer. " Could some one please explain how to check if a particular Y+ is apt for a flow with a particular Reynolds number (or) is there any way to calculate the required Y+ before starting the simulation if the Reynolds number is known __________________ Best regards, Santhosh.

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October 2, 2012, 19:00		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	Sensitivity study - the same answer for just about any adjustable parameter in CFD.