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-   -   Nozzle Thrust (http://www.cfd-online.com/Forums/star-ccm/116343-nozzle-thrust.html)

rietuk April 17, 2013 09:04

Nozzle Thrust
 
Hi,

I am trying to compute the thrust generated from a con-di nozzle.

In the documentation there is a Thrust report shown that appears to be what I am after. However, I am using Star-CCM+ 7.04.006 and I cannot see this report listed in the respective menu.

Is this a recently added feature and if so is there a way to calculate thrust in the version I am using?

I know that T=integral(density * velocity * velocity) ds + integral(P-Pamb) ds
How do compute these surface integrals in Star-CCM+?

Thanks for your help!

rwryne April 17, 2013 15:27

I forgot they recently added a thrust report! I think they did that is v7.06 or v8.02

I've been using this since v5.02, provided by a cd-adapco rep:

-($Pressure*$$Area.mag()-$FaceFlux*$$Velocity.mag())

I set it up as a field function and then do a Sum report for the face I want thrust on


edit: just confirmed this gives exact same value as their "Thrust report" in v8.02

rietuk April 17, 2013 16:06

Hi rwryne,

Thanks very much for your reply. That field function seems to be exactly what I'm looking for.

One quick question - does there have to be a boundary at the nozzle exit plane for this to work?
Or does it work on a derived plane, if so how do i constrain one to the nozzle exit plane or to only take value from that area?

Thanks so much :):)

rwryne April 18, 2013 10:40

Its a bit silly how you you have to do this:

At the part level, make the plane for your nozzle exit using the surface repair tool or some other method.

Export this as an STL, and then import it under Derived Parts as an "arbitrary plane".

rietuk April 20, 2013 05:26

Hi,

Thanks again for the help!
I couldn't get the report to work with an arbitary plane, it just gave me 0.

I then split the model into two parts and ran the sum on the interface between them and got a value. Does this seem like it should work?
I can't seem think of a way to validate the answer

Thank you

rwryne April 20, 2013 19:18

Quote:

Originally Posted by rietuk (Post 421916)
Hi,

Thanks again for the help!
I couldn't get the report to work with an arbitary plane, it just gave me 0.

I then split the model into two parts and ran the sum on the interface between them and got a value. Does this seem like it should work?
I can't seem think of a way to validate the answer

Thank you

Go to your arbitrary plane and make sure its assigned to your Region. Essentially it needs to be imported as a computational surface, therefore it needs a mesh to be computed on...this is accomplished by assigning it to your region. After doing this, open a geometry scene and click on the arbitrary plane and make sure it shows up in the scene....this will verify it imported correctly.

I'm not sure about your method.....


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