| Summary: | A comprehensive investigation was carried out in this study, to evaluate the effect of changing pitching axis position and offsetting mass center displacement on the power extraction performance of a semi-active flapping airfoil power generator (FAPG). Unlike previously published literature, the pitching axis position and the mass center position of the airfoil are not to be located at the same position in the current work. A numerical method for accurately simulating the interaction between the fluid and semi-active FAPG was developed and validated to fulfill this objective. The analysis results showed that the optimized pitching axis position and offsetting mass center displacement are found at the value of d = c/2 and xθ=−0.15c respectively, and compared with the offsetting mass center displacement, the effect of the pitching axis position on the performance of the FAPG is weak. Vortex structure analysis found that the leading-edge vortex is promoted to separate at initial or middle flapping, and it is delayed to separate at down or up flapping, which is the characteristics of the enhanced power extraction performance airfoil.
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