DFBI+Rotation

Alberto Damas · November 2, 2015, 06:29

Hi, I am trying to simulate a wind turbine using both, DFBI and rotation motion. I want to set the wind speed and the angular velocity as inputs in order to get the torque that makes this posible.

I am doing something wrong because the torque I get is the same with different geometry or angular velocity.

Thx.

me3840 · November 3, 2015, 21:20

Why would angular velocity be an input here? You should simply need the freestream velocity.

If you get the same answer with two different geometries, are you sure you remeshed the second geometry?

Alberto Damas · November 4, 2015, 04:43

I need to set the angular velocity or the torque as an input, and I think it's easier for me to set the first one.

I have seen the DFBI superposed rotation motion which does what I was trying to do using DFBI rotation and traslation and rotation separately. This method solves the different geometries problem, so I assume I didn't model the problem well before.

It's much easier now. Thx a lot.

me3840 · November 4, 2015, 14:12

If you are doing DFBI with a turbine, which removes energy from the flow, torque and angular velocity are outputs, they cannot be specified, otherwise you are not doing DFBI, you're just doing RBM.

Alberto Damas · November 11, 2015, 04:34

I was wrong, it didn't work. But I keep thinking I need to set the torque or the angular velocity. I don't understand how it would calculate the torque without DFBI. I remark I am just looking for the steady state, I mean, both angular velocity and torque are constant.

me3840 · November 11, 2015, 12:08

Torque is not calculated if you are not doing DFBI, it is specified (as the rotation speed).

So in general, for each type of simulation, you need some inputs:
1. Steady - requires the use of MRF, the rotation speed (torque) is specified, velocity is measured.
2. Transient with no DFBI - uses RBM (or MRF I guess), the rotation speed (torque) is specified, velocity is measured.
3. Transient with DFBI - uses RBM, the freestream velocity is specified, torque is measured.

November 2, 2015, 06:29	DFBI+Rotation	#1
Alberto Damas Member Alberto Join Date: Aug 2015 Posts: 31 Rep Power: 10	Hi, I am trying to simulate a wind turbine using both, DFBI and rotation motion. I want to set the wind speed and the angular velocity as inputs in order to get the torque that makes this posible. I am doing something wrong because the torque I get is the same with different geometry or angular velocity. Thx.

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November 3, 2015, 21:20		#2
me3840 Senior Member Join Date: Nov 2010 Location: USA Posts: 1,232 Rep Power: 24	Why would angular velocity be an input here? You should simply need the freestream velocity. If you get the same answer with two different geometries, are you sure you remeshed the second geometry?

November 4, 2015, 04:43		#3
Alberto Damas Member Alberto Join Date: Aug 2015 Posts: 31 Rep Power: 10	I need to set the angular velocity or the torque as an input, and I think it's easier for me to set the first one. I have seen the DFBI superposed rotation motion which does what I was trying to do using DFBI rotation and traslation and rotation separately. This method solves the different geometries problem, so I assume I didn't model the problem well before. It's much easier now. Thx a lot.

November 4, 2015, 14:12		#4
me3840 Senior Member Join Date: Nov 2010 Location: USA Posts: 1,232 Rep Power: 24	If you are doing DFBI with a turbine, which removes energy from the flow, torque and angular velocity are outputs, they cannot be specified, otherwise you are not doing DFBI, you're just doing RBM.

November 11, 2015, 04:34		#5
Alberto Damas Member Alberto Join Date: Aug 2015 Posts: 31 Rep Power: 10	I was wrong, it didn't work. But I keep thinking I need to set the torque or the angular velocity. I don't understand how it would calculate the torque without DFBI. I remark I am just looking for the steady state, I mean, both angular velocity and torque are constant.

November 11, 2015, 12:08		#6
me3840 Senior Member Join Date: Nov 2010 Location: USA Posts: 1,232 Rep Power: 24	Torque is not calculated if you are not doing DFBI, it is specified (as the rotation speed). So in general, for each type of simulation, you need some inputs: 1. Steady - requires the use of MRF, the rotation speed (torque) is specified, velocity is measured. 2. Transient with no DFBI - uses RBM (or MRF I guess), the rotation speed (torque) is specified, velocity is measured. 3. Transient with DFBI - uses RBM, the freestream velocity is specified, torque is measured.