[Sideption]

Hey guys,

So I have this question about not any of the software in particular but on the ways and means to solve a problem. My situation right now is that we are designing a new wind blade and would like to study the power generated from the new design when fitted with a generator.

So, what's the right way to go about this problem? I had a few options in my head.

1) To simulate the only the wing itself with Air hitting it along the chord line at a velocity representing relative velocity, getting the lift and drag forces and vectors --> calculating torque and thrust from these numbers as per their angular orientation on the hub blades during assembly --> and reverse calculating the actual velocity from the relative velocity that I've simulated and present it. (not so sure about this approach)

P.S. My prof strongly recommended me doing this as he said that the lift and drag numbers that we get from this along-the-chord simulation can be translated to actual wing during operation in the turbine which im not convinced about as most of the fluent tutorials are doing things like in option 2.


2) To simulate the wings in an actual hub assembly with the wings tilted with a certain pitch (variable one and I'm planning I would optimize it as I run the simulations) and to keep them stationary and simulate a wind hitting head on the hub assembly and calculate the torque generated by using pressure integrals and transferring to static structural and find the torque along the central axis and thus concluding on an rpm that is caused by the wind acting on the wing.

3) To simulate the wings in the uniform rotation and following the same steps as of option 2 and find the torque generated.

P.S. The third option doesn't make sense but most of the discussions here are starting by giving an initial rotational speed and then calculate the torque later. I was under the impression that the rotation by itself is generated by the lift--> torque generated on the wing.

P.P.S The cornell tutorials were following the third option but the burning question is still in my head.

So...it would be incredibly helpful if you could direct me to the right way of approach and if this is the wrong place to ask, I would appreciate if you could direct me to the right place.

Thanks and cheers.
Sid

[Hamidzoka]

Hi;
The appraoch you select strongly depends on the target of your project.
First of all you should answer this question: are you going to design a 3D wind turbine blade or design a proper profile (or a library of profiles) for wind turbine applications?

in case you are doing a profile design item 1 is a proper strategy. and if you are focused on the hole blade design the item 3 seems to be the right choice.

Note that generally in aero-simulations of turbomachines of any kind, rotation of blades should be defined in the software. Since it is just a CFD sofware and not a multi-physics solver. Therefore pressure distributions on the blades can not rotate the blades in it. in other words it can only exert the force on the blades and there is no solid dynamics momentum formulation embedded there to represent the rotation of the blades!!!
If you correctly define the airfoils (dimensions + position) with proper setting of rotation (rpm + direction) in a CFD solver, It truely represents the flowfield. In order to check this you can follow variation of flow parameters through the blades. for example if simulations go right you should expect that total pressure of the wind reduces through the blades as its energy is delivered to them.
I hope it helps

Regards