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Creating a power vs wind speed graph for a VAWT
Hi. I’m trying to build up a power vs wind speed curve for a VAWT. I created a polar for my airfoil at 11 m/s and I think I should create a polar for every step on the curve (3 m/s, 4m/s and so on). While I get reasonable data for 11 m/s, the simulations at low speeds deliver non sense data such as negative Cp. Having said that. Would it be ok to simulate low speed conditions (3 m/s, 4m/s,,) with the 11m/s polars?
Hi,
a negative Cp can be a realistic result at very low Reynolds numbers (for small scale VAWT’s).
That said, you should always cover the typical Renolds number range for the rotor you are investigating. QBlade allows you to define a blade design over a range of reynolds numbers using the multi polar feature, see:
https://docs.qblade.org/src/user/blade/blade.html#multi-polar-blade-definition
BR,
David
