Entropy generation analysis of S825, S822, and SD7062 offshore wind turbine airfoil geometries

Abstract

Offshore wind turbines are of special interest due to their growing importance, and hence comprehensively discussed in this research. Three popular offshore wind turbine airfoil geometries (S822, S825, and SD7062) are studied in this research considering entropy generation. There is no similar work in literature considering entropy generation around these offshore wind turbine airfoils. Computations performed for five different angles of attack 0, 5, 10, 15, and 20° at Re = 106. Viscous entropy generation rate is reported as contour plots, and the effect of flow separation on entropy generation is studied. It is shown that flow separation has a dramatic effect on viscous entropy generation rate. The grows of separation area in the higher angle of attack, produces more entropy due to larger shear layer region. Moreover, it is observed that there is a close relation between entropy generation integral (Irreversibilities) and drag coefficient. Finally, second low efficiency is also computed for examined airfoils at the mentioned angle of attack range, to compare their effectiveness. Focusing on the entropy generation in offshore wind turbine blades is essential and useful for designing and achieving a good aerodynamic performance at the offshore wind turbine airfoil. The results of simulation revealed that there are no significant differences between the entropy generation rates of the investigated airfoils for the angles of attack of less than 10°. But, the SD7062 airfoil has the lowest entropy generation rate at larger angles of attack due to the delay in the flow separation. Also, the results of the second-law efficiency indicated that the S825 airfoil has the best performance at the angles of attack of less than 10°, whilst the SD7062 airfoil has the best performance at the angles of attack of greater than 10°.