[ICEM] Angle of Attack

wolvi_ak · June 21, 2011, 14:20

Hi Friends,
I am analyzing one NACA 662(2)15 wing with 1.5m span and 0.4m chord, i need to change the AOA of the wing to 2.5 deg and find the Drag force. wat can be done to change it.
Also i need some clarifications in the default unit that is taken by ICEM CFD since i deal with meters its confusing me while creating the domain.

Then also, In CFX, the function calculator which gives the forces along x and y direction are drag and lift respectively right ? Pls clarify

PSYMN · June 22, 2011, 09:31

ICEM CFD is essentially unitless.

If your model was in meters, it is in meters in ICEM CFD...

If your model was in cubits, it is in cubits in ICEM CFD.

Usually, I check the length of my model in ICEM CFD (using the measuring tape in the top left corner), to figure out the scale. If I don't like it, I go into the Geometry => Transform options and Scale the model.

Unitlless has been pretty good for ICEM CFD all these years, but I think for 14.0, we may add some unit concept to ICEM CFD that would at least keep track of this for you (tell you what the units currently are) and make scaling as easy as selecting the unit system you prefer. It wouldn't change any other behavior though.

mjgraf · June 22, 2011, 15:49

it would be useful to know the units selected for the imported geometry (opening a model from years ago), but in general we keep track of this ourselves or have a few control points in the geometry. And I agree, if it's not broke, don't "fix it".

wolvi_ak · June 25, 2011, 13:10

Thanks Guys,
But i have drawn my model using ICEM CFD itself,, so here is the thing, i get absurd results wen i analyse a wing of span 1.5metres, 0.4 chord and AOA of 2.5 deg.
I get a lift force from function calculator in CFX POST as 960 N and drag as 120 N.

PSYMN · June 28, 2011, 14:52

So you have decided your model is in meters, just make sure that your boundary conditions (velocity, etc.) are in the correct units also... (velocity would be in m/s, not in/s or mm/hr, etc. Consistency is important.)

Any other issues may be coming from somewhere else...

fher1608 · June 30, 2011, 02:34

In fluent you can define the velocity inlet with magnitude and direction, son you can leave the geometry as it is and change the flow (projecting the speed). That is how I change the AOA

wolvi_ak · August 5, 2011, 09:22

Quote:

Originally Posted by fher1608

In fluent you can define the velocity inlet with magnitude and direction, son you can leave the geometry as it is and change the flow (projecting the speed). That is how I change the AOA

fher1608: so u ask me to give velocity components instead of changing the angle of attack of the model...... thn can u tell me how to evaluate the exact lift and drag forces acting on the model in fluent or ICEMCFD

wolvi_ak · August 5, 2011, 09:23

fher1608: so u ask me to give velocity components instead of changing the angle of attack of the model...... thn can u tell me how to evaluate the exact lift and drag forces acting on the model in fluent or ICEMCFD

fher1608 · August 5, 2011, 10:31

In fluent you can define the projection of the forces. I mean, in monitors you can choose the direction of the drag, and also the lift, so the Cl and Cd calculated will be in that direction. Thats the way I do it and it's easier than changing the geometry

June 21, 2011, 14:20	Angle of Attack	#1
wolvi_ak New Member Karthik Join Date: Jun 2011 Posts: 4 Rep Power: 15	Hi Friends, I am analyzing one NACA 662(2)15 wing with 1.5m span and 0.4m chord, i need to change the AOA of the wing to 2.5 deg and find the Drag force. wat can be done to change it. Also i need some clarifications in the default unit that is taken by ICEM CFD since i deal with meters its confusing me while creating the domain. Then also, In CFX, the function calculator which gives the forces along x and y direction are drag and lift respectively right ? Pls clarify

June 22, 2011, 09:31		#2
PSYMN Senior Member Simon Pereira Join Date: Mar 2009 Location: Ann Arbor, MI Posts: 2,663 Blog Entries: 1 Rep Power: 47	ICEM CFD is essentially unitless. If your model was in meters, it is in meters in ICEM CFD... If your model was in cubits, it is in cubits in ICEM CFD. Usually, I check the length of my model in ICEM CFD (using the measuring tape in the top left corner), to figure out the scale. If I don't like it, I go into the Geometry => Transform options and Scale the model. Unitlless has been pretty good for ICEM CFD all these years, but I think for 14.0, we may add some unit concept to ICEM CFD that would at least keep track of this for you (tell you what the units currently are) and make scaling as easy as selecting the unit system you prefer. It wouldn't change any other behavior though. __________________ ----------------------------------------- Please help guide development at ANSYS by filling in these surveys Public ANSYS ICEM CFD Users Survey This second one is more general (Gambit, TGrid and ANSYS Meshing users welcome)... CFD Online Users Survey

June 28, 2011, 14:52		#5
PSYMN Senior Member Simon Pereira Join Date: Mar 2009 Location: Ann Arbor, MI Posts: 2,663 Blog Entries: 1 Rep Power: 47	So you have decided your model is in meters, just make sure that your boundary conditions (velocity, etc.) are in the correct units also... (velocity would be in m/s, not in/s or mm/hr, etc. Consistency is important.) Any other issues may be coming from somewhere else... __________________ ----------------------------------------- Please help guide development at ANSYS by filling in these surveys Public ANSYS ICEM CFD Users Survey This second one is more general (Gambit, TGrid and ANSYS Meshing users welcome)... CFD Online Users Survey

August 5, 2011, 09:23	lift and drag forces	#8
wolvi_ak New Member Karthik Join Date: Jun 2011 Posts: 4 Rep Power: 15	fher1608: so u ask me to give velocity components instead of changing the angle of attack of the model...... thn can u tell me how to evaluate the exact lift and drag forces acting on the model in fluent or ICEMCFD

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June 22, 2011, 15:49		#3
mjgraf Senior Member Join Date: Dec 2009 Posts: 131 Rep Power: 20	it would be useful to know the units selected for the imported geometry (opening a model from years ago), but in general we keep track of this ourselves or have a few control points in the geometry. And I agree, if it's not broke, don't "fix it".

June 25, 2011, 13:10		#4
wolvi_ak New Member Karthik Join Date: Jun 2011 Posts: 4 Rep Power: 15	Thanks Guys, But i have drawn my model using ICEM CFD itself,, so here is the thing, i get absurd results wen i analyse a wing of span 1.5metres, 0.4 chord and AOA of 2.5 deg. I get a lift force from function calculator in CFX POST as 960 N and drag as 120 N.

June 30, 2011, 02:34		#6
fher1608 New Member Fernando Join Date: Jun 2011 Posts: 6 Rep Power: 15	In fluent you can define the velocity inlet with magnitude and direction, son you can leave the geometry as it is and change the flow (projecting the speed). That is how I change the AOA

August 5, 2011, 10:31		#9
fher1608 New Member Fernando Join Date: Jun 2011 Posts: 6 Rep Power: 15	In fluent you can define the projection of the forces. I mean, in monitors you can choose the direction of the drag, and also the lift, so the Cl and Cd calculated will be in that direction. Thats the way I do it and it's easier than changing the geometry