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2.4.1 Aerodynamic characteristics with difference of aspect ratios
Aerodynamic characteristics of the high mast sail with difference of aspect ratios are shown in Fig.9 in case of the slat angle β=35deg, the boom angle γ=30deg. The setting on the slat and the boom bringing about higher lift was decided by previous experiments [3]. The results of the five kinds of the square soft sails and one triangular soft sail are shown in the figure. Number in the legend of the figure represents AR. It is understood that the lift force coefficients are greatly influenced by the aspect ratio though the drag coefficients are not greatly changed by them. The drag simply depends on the lateral area on the wing, that is, it is thought that the drag is dominated by the pressure drag at this Reynolds number. The maximum lift is recorded as 2.6 in case of LH1(AR=2.63). The lift of the square type sail is larger than that of the triangular one when those sails are same AR. From the viewpoints of the production, however, the triangular sail is superior to the square one.
Fig.10 |
Aerodynamic characteristics of the low mast sail with different aspect ratios (AR=0.65〜1.06, β=35deg, γ=30deg) |
Fig.11 |
Aerodynamic characteristics of the low mast sail with different forms of the soft sail (AR=1.06, β=35deg, γ=30deg) |
Aerodynamic characteristics of the low mast sail with the difference of aspect ratios are shown in Fig.l0 in case of the slat angle β=35deg, the boom angle γ=30deg as same as the previous figure. The results using three kinds of the square soft sails are shown in the figure. The maximum lifts are same level for the three models, but the values are smaller than those of the high mast sails i.e. the higher AR sails.
The effect of the soft sail forms is investigated as in Fig.11. The difference of CL is observed in Fig.9 between the high mast sail of the square sail and the triangular sail that are same AR. In case of the low mast sails in Fig. 11, the difference according to the soft sail form is very small compared with the case of the high ones. Bending of the soft sail is hardly given to the vertical direction for the low mast sail because the model size is relatively small. On the other hand, the tip line of the triangular soft sail of the high mast sail is observed to bend because of long sail length in vertical direction. This is thought as one of the reasons on CL in between Fig.9 and Fig.11.
Fig.12 |
CLMAX and maximum CL/CD(β=35deg,γ=30deg)[SS; Soft Sail] |
Fig.13 |
Effect of the parts on CLMAX(β=35deg,γ=30deg)[SL; Slat,RS; Rigid Sail, SS; Soft Sail] |
Fig.14 |
Effect of the slat angle on CLMAX and CD at CLMAX(γ=30deg) |
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