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Cp and Ct is larger than Bladed
Hi David,
I recently had a problem with the calculation of Cp and Ct values. The Cp value calculated with bladed is less than 0.4 and the Ct value is less than 0.9. while the Cp value calculated with Qblade is greater than 0.45 and the Ct value is greater than 1.2, which seems to be incorrect (see the picture 1~3). The bladed settings are shown in Figure 4 and the Qblade setting are shown in Figure 5. Could you tell me why there is such a big difference between the two software. Is it a result of incorrect parameter settings somewhere?
Looking forward to hearing your reply soon.
Best regards,
Carl
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Hi Carl,
the steady BEM calculations in both QBlade and Bladed should provide correct results, based on the blade geometry and its associated polars. The BEM routines are among the simplest and most thoroughly validated modules in both QBlade and Bladed. Both codes have also been compared directly – for example, see this NREL report: https://docs.nrel.gov/docs/fy24osti/88685.pdf.
So I would assume the reason for the discrepancies come from either a different geometrical definition of the blade, or differences in the underlying polar data. Pinpointing those differences can be tricky, but it is certainly possible if you have access to both the geometry files and the polar datasets.
BR,
David
