Propeller Thrust Method

Aidan.B · October 20, 2015, 22:19

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!

-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.

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.

October 20, 2015, 22:19	Propeller Thrust Method	#1
Aidan.B New Member Aidan Bryant Join Date: Mar 2015 Posts: 2 Rep Power: 0	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!

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October 21, 2015, 03:40		#2
-Maxim- Senior Member Maxim Join Date: Aug 2015 Location: Germany Posts: 415 Rep Power: 11	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?

October 21, 2015, 18:40		#4
Aidan.B New Member Aidan Bryant Join Date: Mar 2015 Posts: 2 Rep Power: 0	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. 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.