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new to CFD, changing angle of attack/incidence?

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Old   April 22, 2012, 10:57
Default new to CFD, changing angle of attack/incidence?
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Benjamin Kim
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I am new to CFD and just learning how to use Star-CCM+. I was able to analyze and simulate a very simple airfoil by following tutorials. However, I do not know how to change the angle of attack. Do I just transform the geometry part by rotating it a certain amount of degrees/radians? Or is it more complex than that? Thank you.
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Old   April 22, 2012, 16:19
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Quote:
Originally Posted by bjk87 View Post
I am new to CFD and just learning how to use Star-CCM+. I was able to analyze and simulate a very simple airfoil by following tutorials. However, I do not know how to change the angle of attack. Do I just transform the geometry part by rotating it a certain amount of degrees/radians? Or is it more complex than that? Thank you.

Depending on your problem type, you do not need to rotate the geometry.... just change your farfield boundary conditions to reflect new velocity values (i.e. use the directional scalars of the velocity vector to "rotate" the flow)
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Old   April 23, 2012, 15:42
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Quote:
Originally Posted by bjk87 View Post
I am new to CFD and just learning how to use Star-CCM+. I was able to analyze and simulate a very simple airfoil by following tutorials. However, I do not know how to change the angle of attack. Do I just transform the geometry part by rotating it a certain amount of degrees/radians? Or is it more complex than that? Thank you.
It depends on your boundary conditions, but another way is to simply have the velocity inlet to have flow at an angle relative to the inlet instead of purely normal.
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Old   April 23, 2012, 17:05
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Oh, I see. Thanks.
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Old   August 18, 2015, 16:13
Default angle of attack in STARCCM+
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rangel
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Hello all,

I changed the velocity components to obtain an angle in an airfoil but I am having negative drag. Anyone knows why? The lift is ok.

In other simulation, I changed the angle of attack in CAD program and imported for STARCCM+, thus I know the right values. I just would like to be able to change the angle of attack IN the STARCCM.

And you know other ways to do this? I couldn't understand the ways in the tutorial.
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Old   August 19, 2015, 12:34
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Hello all,

I changed the velocity components to obtain an angle in an airfoil but I am having negative drag.
Did you update the direction vector for the drag and lift?
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Old   August 20, 2015, 15:42
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1. As LuckyTran implied but did not specify, your drag vector must point in the same direction as freestream flow. Lift is perpendicular to that. So if you are changing your velocity vector then your force vectors must change too. You can also define the vectors along the chord line and normal to the chord line to get normal and axial force, then simply transform those using: L=N*cos(AOA)-A*sin(AOA), and D=N*sin(AOA)+A*cos(AOA).

2. No need to rotate in CAD if you want to move model WRT flow direction. There is a transform and rotate function if you right click the geometry under parts and select transform > rotate. Then define origin, axis and angle to get your model pointed in the right direction. You will have to remesh.
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