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Old   February 15, 2021, 13:31
Default unsteady rotation
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Hello everybody.

I am trying to replicate in ANSYS Fluent the study of this paper:

It concerns the evaluation of the static and dynamic derivatives of the UCAV SACCON aircraft.

However I have few questions , which I hope you can answer.
I am planning to use the dynamic mesh to compute everything, implementing an UDF with the DEFINE_CG_MOTION macro, where the inputs are the cg translational velocity component and angular velocity components.

Regarding the evaluation of the CM_alpha, I have to impose an additional angle of attack which should be transformed ".. to additional velocity perpendicular to free-stream velocity..". What does this mean? How can I increase the angle of attack unsteadily? where should I input this increase in velocity? To me it makes no sense to impose a translational cg motion because otherwise the whole body will move vertically. AM i wrong? It looks that the change in angle of attack is done by this change in velocity. Should I just change the velocity components in the boundary conditions of the inlet? It looks simple, but I am really lost.

The same applies to the CM_alpha_dot, in which the angle of attack and, hence, the velocity has a linear variation in time with a constant rate.

Regarding the CMq, instead is easier because I simply use the dynamic mesh with the CG_MOTION macro and input an angular velocity of constant value.

I am sorry for this long message, but I really want to explain the problem for all of you to understand my particular issues.

If you need additional infos, please let me know.

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Old   July 24, 2021, 01:50
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Hi Alessandro,

Have you found the procedure to solve this problem in Fluent?

Even I am also interested to simulate in Fluent to estimate the dynamic stability derivatives.

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angle of attack, dynamic, rotating, unsteady

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