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CFD analaysis of Pelton turbine

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Old   June 3, 2013, 07:29
Default Jet Deflection
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Amod Panthee
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I still have the problem with jet deflection. Earlier the jet was deflected in negative direction due to error in assigning the volume fraction of air and water during initialization. But, now the jet is deflected slightly in positive direction of rotation. Initially the jet is not fully developed, therefore, it deflects much (attached picture). But at 3 timesteps which includes timestep 19 to 21, the jet travels in straight path (attached picture). From timestep 22 to the end of simulation the shows small deflection in its flow direction (attached picture). What might be the reason for this?
Does this happen due to improper mesh quality? I have not worked much on meshing in this simulation. And defined maximum possible finer mesh possible without any manual modifications at specific locations.
Thanks in advance!
Attached Images
File Type: jpg timestep_9.jpg (82.1 KB, 30 views)
File Type: jpg timestep_20.jpg (82.5 KB, 24 views)
File Type: jpg timestep_91.jpg (86.4 KB, 27 views)
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Old   June 3, 2013, 07:34
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Glenn Horrocks
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This effect might be real - have a search for the Coanda effect.

But if you are convinced this is wrong then firstly read the FAQ: http://www.cfd-online.com/Wiki/Ansys..._inaccurate.3F

If you want us to help you more you will need to show some views in the other plane, your CCL and other details so we can understand what you are doing.
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Old   June 5, 2013, 05:19
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Hannes
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Can you show a plot of isosurface of water.volumefraction? I think it will show a reasonable result...
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Old   June 5, 2013, 06:13
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Sijal Ahmed Memon (turboenginner@gmail.com)
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Quote:
Does this happen due to improper mesh quality? I have not worked much on meshing in this simulation. And defined maximum possible finer mesh possible without any manual modifications at specific locations.
what do you mean by improper mesh quality? Would you like to please show us some images?

where you have finer mesh? is there any sudden change in cell volume? You can always make the manual modification in mesh and it is good idea to follow the general (best practices) for meshing of turbomachinery!!! specially at the interface.
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