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-   -   [ICEM] Angle of Attack (http://www.cfd-online.com/Forums/ansys-meshing/89749-angle-attack.html)

wolvi_ak June 21, 2011 13:20

Angle of Attack
 
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.:confused:
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 08:31

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 14:49

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 12:10

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 13:52

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 01:34

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 08:22

Quote:

Originally Posted by fher1608 (Post 314158)
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 08:23

lift and drag forces
 
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 09:31

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


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