Calculating The Torque From The Angle Of Shaft or Propeller’s Normal Axis

butterflymuzzy · October 28, 2020, 10:39

Hello Glenn and the other members,

I Want to calculate the relative rotative efficiency of a ship’s propeller. Relative rotative efficiency equals to (open water Torque/ship shaft axis Torque) of a propeller.

It is easy to calculate the Open water torque or thrust(force) from x,y and z axises. Like torque_x()@propeller or force_x()@propeller.

What I did is, when I calculate the wake of the propeller with ships hull and appendages, I easily insertEd the new axis and rotated my propeller around the inserted new axis (3 degrees shaft axis).

But the problem is how can I monitor or calculate the torque of a propeller from the new axis (ship’s shaft 3 degrees angular normal axis). It might be a expression or I can look from results with a method ?

Best.

Opaque · October 28, 2020, 15:41

If you can create a local coordinate frame oriented as you want, you should be able to

torque_x_MyInclinedCoord()@Boundary

In fact, you check the correct syntax using the CFD-Post calculator, and toggle the "write the expression".

October 28, 2020, 10:39	Calculating The Torque From The Angle Of Shaft or Propeller’s Normal Axis	#1
butterflymuzzy Member Join Date: Mar 2016 Posts: 32 Rep Power: 10	Hello Glenn and the other members, I Want to calculate the relative rotative efficiency of a ship’s propeller. Relative rotative efficiency equals to (open water Torque/ship shaft axis Torque) of a propeller. It is easy to calculate the Open water torque or thrust(force) from x,y and z axises. Like torque_x()@propeller or force_x()@propeller. What I did is, when I calculate the wake of the propeller with ships hull and appendages, I easily insertEd the new axis and rotated my propeller around the inserted new axis (3 degrees shaft axis). But the problem is how can I monitor or calculate the torque of a propeller from the new axis (ship’s shaft 3 degrees angular normal axis). It might be a expression or I can look from results with a method ? Best.

October 28, 2020, 15:41		#2
Opaque Senior Member Join Date: Jun 2009 Posts: 1,804 Rep Power: 32	If you can create a local coordinate frame oriented as you want, you should be able to torque_x_MyInclinedCoord()@Boundary In fact, you check the correct syntax using the CFD-Post calculator, and toggle the "write the expression". __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

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