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Gurney flaps in sailing, do they help?

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8 wind tunnel and with a Re c =2×10 6 . Here, this data base is reported. The comparison of pressure distribution for various device heights shows that Gurney flap considerably increases the aft loading of the airfoil but it also noted that much of the lift increment is caused by a general increase in loading and by a higher suction peak See Fig 4a and 4b to compare pressure distribution on the clean and modified airfoil, also as the Gurney flap height is increased higher loading is noted along the entire airfoil. The lift and drag coefficient, respectively C l and C d , are presented in Fig. 5a and 5b, with an angle of attack from 0° to 15°. The addition of the Gurney flap produces a considerable lift increment compared to the baseline configuration. Larger flap produce larger increment in maximum C l , but not proportionally: 13% for the smallest and 32% for the biggest. Fig. 6 shows the drag polar for the same configuration. At low to moderate C l , there is a drag penalty which increases with flap height; however, at higher C l the drag is significantly reduced. The effect on the maximum L/D is small, but the C l for a given L/D is significantly increased. Finally, the nose-down pitching moment coefficient C m about 0.25c is shown in Fig. 7, it increases with Gurney flap height although not proportionally. With the idea to stow the flap during cruise to eliminate drag increments at lower C l , Storm and Jang have considered a miniature split flap with a 90° deflection, see Fig. 8. Two configurations were tested for a 1.25%c split flap with a hinge line located forward of the trailing edge by 1.0 and 1.5 flap height, respectively. Fig. 9 illustrates that these configurations yielded essentially the same results as the 1.25%c Gurney flap without degradation in flap effectiveness.

Anteprima della Tesi di Floriano Bonfigli

Anteprima della tesi: Gurney flaps in sailing, do they help?, Pagina 8

Tesi di Laurea

Facoltà: Ingegneria

Autore: Floriano Bonfigli Contatta »

Composta da 151 pagine.

 

Questa tesi ha raggiunto 1595 click dal 12/07/2004.

 

Consultata integralmente 2 volte.

Disponibile in PDF, la consultazione è esclusivamente in formato digitale.