## Fluids

Topics relate to Fluent, CFX, Turbogrid and more

#### Regarding angular velocity of zone

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• srivastavatanuj
Subscriber
Hello,nWhen we define velocity we use something like u[0] for X-direction velocity, u[1] for Y-direction velocity etc. If I am defining rotational velocity of the whole fluid zone using ZONE MOTION macro then will the meaning remain the same for angular velocity or w[0] will become velocity of XY plane (rotation about Z), w[1] become velocity of the YZ plane (rotation about X). Am I correct? I am asking this as I am getting this behavior while using UDF.n
• Rob
Ansys Employee
Assuming it's the same as here https://ansyshelp.ansys.com/account/Secured?returnurl=/Views/Secured/corp/v211/en/flu_udf/flu_udf_sec_define_aniso_diffusivity.html and the panels are similar for a velocity inlet nnThe coordinates will be [0], [1], [2] x, y, z or radial, tangential, axialnI'd advise checking carefully though! n
• srivastavatanuj
Subscriber
nnOrigin is at the center on bottom section. I gave angular velocity UDF as omega[0] = some function of time inside the cell zone condition. omega[0] seems to be rotation about X axis,nbut it is looking like rotating about Z-axis (XY plane). n
• Rob
Ansys Employee
Check what the centre line is defined as in the cell zone. Default is origin in 0, 0, 0 axis in z-axis. n
• srivastavatanuj
Subscriber
Yes, but sir after compiling UDF, all options disappear (see the image). If UDF is not loaded, then the point you said can be checked. So I am giving w[0], w[1], w[2] and getting the thing I mentioned above.nn
• Rob
Ansys Employee
That's the cell zone, what are you doing? n
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