[AARcee]

Hi

I have been simulating a HAWT using Sliding Mesh in Star CCM+. Initially I made the turbine rotate at a fixed rotation rate and when the flow was developed the blades were made to rotate under the influence of fluid forces(Torque=Moment of Inertia*angular acceleration) . Eventually the windmill starts rotating at a constant angular velocity for a particular wind speed and the torque acting on the blade becomes zero. So far So good.

Now I want to calculate power produced by the windmill. So I used the formula Power= Torque*angular velocity . Eventually the turbine starts rotating at a uniform rotation rate and the torque acting on the blade is zero. According to this the power produced by the windmill is zero. This seems contradictory. won't the windmill keep on producing power?. In my case a finite value of power is produced only during the transient case, when the windmill is on its way to attain a uniform rotation rate under the influence of fluid forces , and once it starts rotating at a fixed angular velocity, the torque goes to zero and so does the power .

[robo]

It sounds like your turbine is free-wheeling, ie spinning with no resistive load. In reality the generator will apply a resistive load on the turbine, and it is the work done by the rotor to overcome this resistance that is converted to electrical power. The rotation rate of a turbine in free-wheel will be different from the rotation rate under load. You'll need to add an appropriate power take-off system to your simulation in order to get a realistic power production.