Reference values in FLUENT

RON1991 · July 24, 2015, 03:48

Hi everybody,

I have a doubt about the "reference values" in FLUENT.

I want to simulate a H-rotor DARRIEUS, with these characteristics :
. H=0.4m
. R=0.3m
. S=2*R*H=0.24m²
What are the values for "Depth" and for "Length" in FLUENT ??
I thought that "Depth"=H, and "Length"=R...
BUT I've seen that if I double the value of "Depth" in the reference values, the moment coefficient (Cm) is also double; however, Cm=C/(0.5*ro*S*R*Uinf²), isn't it ? So with the same values of "length" and "Area", Cm would be the same, no ?

Thank you very much for your explanations !

LuckyTran · July 24, 2015, 10:30

The depth property is only for 2D simulations for scaling of the cell volumes in the "depth" direction.

In 3D you would be correct (although there would be no depth reference). However, in 2D you cannot increase the depth while keeping the physical area constant (since the force is the product of the pressure and physical area). That is, when you double the depth you double the area over which the pressures act and hence the force is doubled.

RON1991 · July 28, 2015, 11:53

Thank you very much for your answer LuckyTran

July 24, 2015, 03:48	Reference values in FLUENT	#1
RON1991 New Member Join Date: Apr 2015 Posts: 2 Rep Power: 0	Hi everybody, I have a doubt about the *"reference values"* in FLUENT. I want to simulate a H-rotor DARRIEUS, with these characteristics : . H=0.4m . R=0.3m . S=2RH=0.24m² What are the values for "Depth" and for "Length" in FLUENT ?? I thought that "Depth"=H, and "Length"=R... BUT I've seen that if I double the value of "Depth" in the reference values, the moment coefficient (Cm) is also double; however, Cm=C/(0.5roSRUinf²), isn't it ? So with the same values of "length" and "Area", Cm would be the same, no ? Thank you very much for your explanations !

July 24, 2015, 10:30		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,665 Rep Power: 65	The depth property is only for 2D simulations for scaling of the cell volumes in the "depth" direction. In 3D you would be correct (although there would be no depth reference). However, in 2D you cannot increase the depth while keeping the physical area constant (since the force is the product of the pressure and physical area). That is, when you double the depth you double the area over which the pressures act and hence the force is doubled. RON1991 likes this.

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July 28, 2015, 11:53		#3
RON1991 New Member Join Date: Apr 2015 Posts: 2 Rep Power: 0	Thank you very much for your answer LuckyTran