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Old   February 11, 2015, 16:58
Default Transient profile data
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I will soon be applying a time-varying profile data as a boundary condition similar to what is outlined here. As I've never done this before and am still very new to CFX (and CFD) in general, I'm quite nervous about this, and Ansys help hasn't been much help.


1. Is it normal to make time a "spatial field" as in the linked example?
2. My input profile data is 1D (or 2D including the time variable), that is to say velocity as a function of radius. Does CFX automatically apply that to the planar inlet with the understanding that r = sqrt(x^2+y^2)? Does that mean that the flow has to be in the Z direction and the inlet on the XY plane in the model?
3. Ansys Help example ( Profile Data Format) shows cylindrical spatial fields, but Cartesian data. Why is this?

[Spatial Fields]
r, theta, z
X [ m ], Y [ m ], Z [ m ], Area [ m^2 ], Density [ kg m^-3 ]
-1.773e-02, -5.382e-02, 6.000e-02, 7.121e-06, 1.231e+00
-1.773e-02, -5.796e-02, 5.999e-02, 5.063e-06, 1.231e+00
4. If anyone can point to a tutorial or introduction for this, whether in Ansys documentation or on the web, I'd much appreciate it. Thank you.
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Old   February 13, 2015, 07:18
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You can use an input file such as this:

Transient Radial

[Spatial Fields]
r, Time

r [m], Time [s], Ur [m/s]
0.00000e+00, 0.00000e+00, 1.00000e+00
1.01010e-03, 0.00000e+00, 9.99999e-01
2.02020e-03, 0.00000e+00, 9.99999e-01
3.03030e-03, 0.00000e+00, 9.99999e-01
4.04040e-03, 0.00000e+00, 9.99999e-01
0.00000e+00, 1.25000e+00, 1.25000e+00
1.01010e-03, 1.25000e+00, 1.24999e+00
2.02020e-03, 1.25000e+00, 1.24999e+00
3.03030e-03, 1.25000e+00, 1.24999e+00
4.04040e-03, 1.25000e+00, 1.24999e+00

I grouped values by time (2nd column) but you can do it anyway you like. Notice I used 'r' for position, so to use this table in CFX, call it with Transient Radial.Ur(sqrt(y^2 + z^2), Time) if you're using X as your axial direction.
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Old   February 14, 2015, 15:03
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Thanks, Brunoc. The BC appears to be working, but the profile becomes uniform as the fluid travels through the cylinder. Any ideas what's wrong?

The geometry is an empty 1/6 axisymmetric cylinder.

Update. I've opened a new thread for this follow up question: Inlet profile becomes uniform. Please answer there.

Last edited by bongbang; February 14, 2015 at 15:20. Reason: add image
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boundary condition, profile

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