The following paper deals with the differences between full-span and semi-span testing in wind tunnels. The main objective behind this investigation was to quantify the effect of the stand-off, also known as the peniche, on the aerodynamic coefficients. To determine the influence of the peniche and to avoid disturbance between full-span and semispan testing a new concept of a divided testsection was used. Combined numerical and experimental studies have shown that the deviation of the aerodynamic coefficients between full-span and semi-span testing increases with increasing peniche thickness. The vortex, which develops on the wall in front of a standard two-dimensional peniche, has a major influence on the flow around the model. This is especially noticeable at the root of the wing where the separation behaviour of the flow is greatly affected. Additionally, with the two-dimensional peniche, the pressure difference between the top and bottom side of the fuselage was exaggerated. This effect explains the large deviation in the aerodynamic coefficients between the full-span and the semi-span models. Furthermore, the present results have shown that it is beneficial to remove the peniche and to leave a gap between the model and the wall. This effectively removes the recirculation zone in front of the fuselage and the pressure difference between top and bottom side of the fuselage is equivalent to the pressure difference of the full-span model itself. These findings ultimately lead to an optimal gap size of four times the displacement thickness of the tunnel wall boundary layer in front of the fuselage.
Semi-span testing in wind tunnels
Halbspannweitenprüfung in Windkanälen
2006
9 Seiten, 19 Bilder, 10 Quellen
Aufsatz (Konferenz)
Englisch
SEMI-SPAN TESTING IN WIND TUNNELS
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