For real-life situations, viscous calculations are necessary. Please note that these outcomes only concern inviscid, so “theoretical” results. Finally, it has been observed that all the methods perform equally well when regular design parameters of current turbines are applied. This alteration has been verified to produce the correct result, and could therefore be used to compare the transformed airfoils to. With a small modification, the option to also include the additional surface velocities of a rotating VAWT airfoil was added. This inviscid potential flow solver uses singularity solutions placed on the airfoil surface to compute the airfoil characteristics, such as pressure distribution and aerodynamic forces.
Turbine airfoil code#
The virtual airfoil transformation solutions have been computed by the use of the U2DIVA panel code (Simão Ferreira, 2009). A visual inspection and a calculation of their pressure distribution showed that for common chord-to-radius ratios below 0.2 (Kirke, 1998), no distinguishable differences or advantages of any method could be found. Their transformations have been applied to investigate any performance differences. One can imagine that if this ratio increases, the variation of angle of attack over the chord will increase, resulting in enhanced flow curvature effects. An important parameter in all these methods is the chord-to-radius ratio of the turbine. Several authors present methods to perform such a virtual airfoil transformation, while only six of these describe their work detailed enough to be reproduced.
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