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-   -   Propeller Thrust Method (https://www.cfd-online.com/Forums/cfx/161262-propeller-thrust-method.html)

Aidan.B October 20, 2015 22:19

Propeller Thrust Method
 
Hi All,
I'm attempting to calculate the thrust generated by an RC aircraft propeller and I'm wondering about my method.
I made a small cylinder around the propeller shape and subtracted it. I then made a second cylinder the exact same size, and a larger cylinder and subtracted the smalle from the large to give me two domains, the outer domain and inner domain with cylinder cut out. In CFX I set an interface between the two, input, output and walls on the larger cylinder and set the propeller shaped cut out to be a wall. I've then rotated the inner domain. My trouble is that this rotated the air within the domain, as well as the propeller walls. Is there a way that I can make the air continue its expected path until acted upon by the propeller? Have I gone about this in the wrong way.

I have looked through the rotor-stator tutorial, but as I understand, the whole stator will be rotating along with the blades, so, it doesn't quite match my problem.

Thanks in advance!

http://s9.postimg.org/dbusn7stb/2_2.png

http://s9.postimg.org/jqttjvzj3/2_3.png

-Maxim- October 21, 2015 03:40

can you please post pictures of your settings? How did you set up your inner domain?
I would make the inner domain smaller - basically only around the propeller.
Did you use Stage interface or Frozen Rotor?

ghorrocks October 21, 2015 06:49

Quote:

My trouble is that this rotated the air within the domain, as well as the propeller walls.
This is a FAQ: http://www.cfd-online.com/Wiki/Ansys...f_reference.3F

It is all good, you are just not viewing it as you expect.

Aidan.B October 21, 2015 18:40

Maxim,

I've used Frozen Rotor.

I've attached the inner domain settings. The domain has a wall as the propeller, and an interface around the outside.
http://s30.postimg.org/9efz8x68h/Untitled.png

My force calculations on the propeller give a result in the range of 0.001 N, where I'm expecting 1-10 N. Would my method be close to what I require, or should I be using an immersed solid?

Thanks ghorrocks, that is much more like I expected.


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