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360 degree fluid zone for a 4 blade propeller

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Old   June 25, 2010, 16:47
Default 360 degree fluid zone for a 4 blade propeller
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Hi to all here! This is my first post in this forum

Now regarding the question:

I created a propeller geometry using the BladeModeler component system and consequently meshed it using turbogrid by using the provided tutorials as reference. No problem there.

So having prepared and produced the mesh in turbogrid, I now start the CFX analysis (Setup/Solution/Results) component on the Ansys 12 Project Management Desktop and retrieve the mesh I created.

Now, the problem begins here:

I have generally noticed that when I import the mesh of the propeller from turbogrid, it always provides me with a fluid zone for only 1 out of the 4 blades. For example one can look at file CFX2.png, where I have set all the appropriate BCs before starting the solution run.

Is it not possible to create a fluid zone that is 360 degrees, incorporates all 4 blades between the inlet and outlet ?

Having solved the problem as steady-state, and arrived to the CFD-Post part, I found that the only way to produce all 4 blades was from changing the number of domain copies to '4' somewhere in the basic setting tab, which is obviously not correct. For example, see CFX5a.png, the velocity streamlines cant be indentical from each blade (I used 'vertex' graphics option for distribution of streamlines with variable being velocity)

The main reason behind all this, is because im trying to produce a working 360 degree fluid zone for the propeller model which will be inserted into a model of a unique channel wing I created in DesignModeler.Then Im hoping that I can introduce working BCs and Interfaces on both of these channel wing & propeller domains in order to finally calculate the lift produced over the whole channel wing !!

Sorry for this huge post, just wanted to be as detailed as I can in order to get the help I definately need.

Thanks!!!

CFX2.png


CFX5a.png
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Old   June 26, 2010, 07:36
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I am not familiar with BladeModeller so cannot help you there. But it looks like the simulation you performed was just on a 90 segment. The 360 display you got in your second image is just a post-processing thing. It just repeats the segment around 4 times to get the full geometry.

Somehow you will need to get BladeModeller to give you a full geometry. Alternately you can take the 90 wedge and duplicate it around in CFX-Pre to create the full geometry.
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Old   June 26, 2010, 07:42
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And that is exactly my problem! I dont want to simulate just the 90 degree segment, but the whole 360 degree region together!

I mean, to be realistic, not all locations downstream of each blade must have identical streamlines.

So there surely must be a way of having a propeller inside a cylindrical domain that encompases it and can be made to interact with a larger domain outside of it?

Or am I making a huge mistake somewhere

*edit*
Is there perhaps someone who knows the settings in BladeModeler/DesignModeler/Turbogrid where this 360 deg fluid zone can be specified before inputting it into CFX-Pre??

Here is also my project schematic, just to confirm that my layout for each step towards the problem setup is correct


Last edited by s0me0ne; June 26, 2010 at 07:53. Reason: added info and pic
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Old   June 26, 2010, 08:04
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The the CFX tutorial flow in a axial rotor/stator and you will see how to combine rotating and stationary domains.

You missed in my previous post that you can also duplicate mesh regions in CFX-Pre, so you can take your 90 segment and copy it around and do the simulation on the full 360.
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Old   June 26, 2010, 08:07
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Quote:
Originally Posted by ghorrocks View Post
You missed in my previous post that you can also duplicate mesh regions in CFX-Pre, so you can take your 90 segment and copy it around and do the simulation on the full 360.
But does this copying mean that you just duplicate the results of one segment all around?
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Old   June 27, 2010, 07:09
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No. If it is CFX-Pre you are setting up the mesh for the simulation. If it is CFD-Post it is just a post-processing thing. Just try it and find out for yourself - that is the best way.
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