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Old   April 24, 2013, 08:40
Question wind turbine simulation
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Hi all,

I just started using fluent and I'm working on a simulation to study the torque from a wind turbine. Please I want to know if there is anyway I can specify the inlet velocity and fluent calculated the turbine rpm? All the simulations I've seen, both the inlet velocity and the turbine rpm are specified.

I'll highly appreciated your feedback.

Thanks
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Old   April 24, 2013, 09:05
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It is possible but then you need to specify the relationship between inlet velocity and rotor speed. For example, you may keep the tip velocity ratio to a prescribed value, or you have a prescribe control strategy.
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Old   April 24, 2013, 15:16
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No Fluent will not calculate RPM for you.
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Old   April 26, 2013, 04:21
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Thanks Far for your comment. But my point is, if it is possible to specify just the wind speed alone in order to get the torque of power from the post results. Assuming I only know the value of the wind speed and no other property or specification of the turbine.

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Old   April 26, 2013, 04:29
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No. You must specify RPM, incoming air direction (mostly zero degree) and airspeed and outlet pressure. Outlet pressure is 101325 for most of the cases but if you want to find the performance at some height then you will have to change the outlet pressure and density.

For this you have to plot the data and find out the optimum point (or required value) on the graph.

Now you must be thinking why we should use CFD if it is not giving me the answer

So answer is CFD does not know what should be the optimum RPM (tip speed ratio in your case ) against incoming air. You have to plot tip speed ratio vs power coefficient to determine the optimum RPM.

So you have specified the inlet velocity (free stream air velocity) and RPM. You will get torque, power (torque * omega), corresponding tip speed ratio. Now I must tell that you can't get the accurate torque and other values analytically. Here where CFD is useful. But definitely CFD cannot (and will not) replace human

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Old   April 26, 2013, 04:59
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Thanks Far, this problem has left me confused for a while now. Actually, I built the turbine myself, so I guess I have to do some experiments to get the tip speed ratio and power coefficient at various wind speed.

Thanks once again.
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Old   April 26, 2013, 05:02
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Well. CFD is also known as numerical wind tunnel.

So you can perform your experiments in CFD and it is better to reduce the no. of designs for the final experimental testing.

Quote:
So answer is CFD does not know what should be the optimum RPM (tip speed ratio in your case ) against incoming air. You have to plot tip speed ratio vs power coefficient to determine the optimum RPM.
Well in your experiments incoming air will rotate the turbine but experiments again would not tell whether it is optimum or not. Moreover if your design is totally wrong then you will have to build another model for testing . And also you will need many runs to reach the conclusion and hence you should be ready for huge expenses. While in CFD your cost is almost negligible...

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