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Moving reference frame for turbine simulation

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Old   November 29, 2017, 09:07
Default Moving reference frame for turbine simulation
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Nicholas Rahl
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----------I have solved the issue, if you are experiencing the same issue please feel free to message me----------------

Overview of simulation
I am attempting to simulate a turbine by create a moving reference frame for the rotation and velocity inlet boundaries to simulate the ambient velocity.
The over all result should be the correct inflow velocity magnitude and direction over the span of the blade.

Simulation set up

For the spacial domain and discretion:
The geometry and mesh of a blade section can be seen in figure 1. I created the geometry by subtracting the blade from the fluid domain.
The directed mesher was used to mesh the resulting part.

For the region set up:
The part was assigned to one region.
The boundaries in use are the velocity inlet on one side, pressure outlet on the opposite side, walls on either side of the blade section with the shear stress specification set to "slip", and wall for the blade section surface itself.

A user define reference frame was created, with the origin and axis set in accordance to the simulation Lab Frame (see figure 2). The "Motion specification" node in physics values of the region was set for this reference frame.
All of the boundaries, except for the blade section surface, had the "Reference frame specification" set to the Lab Frame.
The blade section surface was set as "Region Reference Frame".

The issue

The relative velocity angles are incorrect.

I am unsure what the cause for this is, but i believe it is to do with my definition of which boundaries are rotating. A vector scene can be seen in figure 3 and 4 for the velocity magnitude in terms of the lab frame for the far and near walls (near and far in terms of position to the moving reference frame origin). As you can see from figures, the velocity is angled, with the velocity on the far wall being towards the blade section and for the near wall, away from the blade section.

This affects the relative velocity angle and magnitude and figure 5 and 6 show the relative velocity for the near and far wall respectively.

Surely the vector scenes for the velocity magnitude in terms of the lab frame should show the velocity going in one direction rather than angled? I have tried multiple configurations of the reference frame specification for the boundaries but to no avail. I also tried to create a two regions instead of just one; where one would be for the fluid domain and one for the blade. This was to set the motion specification for the blade region to solely rotate but i was unable to do this due to the limitations of the directed mesher being unable to mesh both parts when they are not subtracted.

Any help would be much appreciated and sorry this is quite lengthy! If i have not specified any key points please let me know.

Kindest regards,

Last edited by Rahl141; December 1, 2017 at 15:22. Reason: I found the solution
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Old   November 29, 2017, 09:08
Default Figure 6
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Nicholas Rahl
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This is figure 6 (5 image cap)
Attached Images
File Type: jpg Figure 6 Far wall relative velocity scene.JPG (127.4 KB, 22 views)
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Old   December 28, 2017, 06:25
kiran Ambilpur
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have you created two fluid regions (one for rotating frame and another for housing, though both are fluid regions)? or only one fluid region ?
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moving reference frames, relative flow, star ccm+

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