y+ and y* values in Fluent

HLYBoy · December 5, 2011, 16:39

I've been running a nozzle case with a standard k-epsilon turbulence model and when I plot the y+ against the distance down the nozzle, the velus I get range from about 16-35. In the Fluent Theory Guide, it tells me to use a y* > 15 and I believe that y* and y+ are effectively the same.

But, I've now heard that I need a y+ of greater than 30 otherwise the errors get too large.

Does this mean my y+ values have been way too small?

Thanks in advance!

HLYBoy · December 5, 2011, 16:58

The Fluent Guide says that the range of y+ values for which wall functions are suitable depends on the Reynolds number, but the lower limit lies in the order of y* or about 15, so I went by that definition.

December 5, 2011, 16:39	*y+ and y values in Fluent**	#1
HLYBoy New Member Join Date: Nov 2011 Posts: 8 Rep Power: 14	I've been running a nozzle case with a standard k-epsilon turbulence model and when I plot the y+ against the distance down the nozzle, the velus I get range from about 16-35. In the Fluent Theory Guide, it tells me to use a y* > 15 and I believe that y* and y+ are effectively the same. But, I've now heard that I need a y+ of greater than 30 otherwise the errors get too large. Does this mean my y+ values have been way too small? Thanks in advance!

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December 5, 2011, 16:58		#2
HLYBoy New Member Join Date: Nov 2011 Posts: 8 Rep Power: 14	The Fluent Guide says that the range of y+ values for which wall functions are suitable depends on the Reynolds number, but the lower limit lies in the order of y* or about 15, so I went by that definition.