Influence of leading edge imperfections on the aerodynamic characteristics of NACA 63₂-215 laminar aerofoils at low Reynolds numbers

Abstract

This article deals with the effect of leading edge imperfections on the aerodynamic characteristics of a NACA 63 2 -215 laminar aerofoil at low Reynolds numbers. Wind tunnel tests have been performed at different Reynolds numbers and angles of attack and global aerodynamic loads were measured. To perform these tests, a NACA 63 2 -215 aerofoil was built up in two halves (corresponding to the upper side and to the lower side), the leading edge imperfection here considered being a slight displacement of half aerofoil with respect to the other. From experimental results, a quantitative measure of the influence of the leading edge displacement on the degradation of the aerofoil aerodynamic performances has been obtained. This allows the establishment of a criterion for an acceptance limit for this kind of imperfection.

Galloping instabilities of Z-shaped shading louvers

“…In these previous tests, pressure distributions were measured, and recorded, at 125 Hz sampling rate during 10 s. This test was used to evaluate the two-dimensional character of the flow acting on the aerofoil, as it was demonstrated from the comparison of measured pressure distributions at different span locations, where no significant differences were found. 31,33…”

“…In these previous tests, pressure distributions were measured, and recorded, at 125 Hz sampling rate during 10 s. This test was used to evaluate the two-dimensional character of the flow acting on the aerofoil, as it was demonstrated from the comparison of measured pressure distributions at different span locations, where no significant differences were found. 31,33 Once a selected model was fixed to the rotating platform, angles of attack were varied from a = 0° to a= 180° at 2° steps, and at each step the six outputs coming from the strain-gauge balance were stored in a PC, as well as the dynamic pressure inside the test chamber. The averaging period used for the mean force coefficients measurements was 10 s at a sampling frequency of 20 Hz.…”

Static and Dynamic Experimental Analysis of the Galloping Stability of Porous H-Section Beams

“…All of them are of 158 mm span, thus leaving a 1 mm gap between the wind tunnel walls and the lateral surfaces of the models. It must be pointed out that this gap does not affect the two-dimensional behaviour of the model; the reasons are that these gaps are very narrow and they are placed at the boundary layers that develop at the wind tunnel walls [ 19 ]. Bodies are fixed to the balance through a 12 mm steel rod, placed at the centre of mass of the models, as sketched in Figure 1 .…”

Influence of aerodynamic characteristics of H beams on galloping stability

“…All of them are 158 mm span, thus leaving a 1 mm gap between the wind tunnel walls and the lateral surfaces of the models. It must be pointed out that this gap does not affect to the two-dimensional behaviour of the model, the reasons being that these gaps are very narrow and they are placed at the boundary layers that develop at the wind tunnel walls [5].…”

“…It must be pointed out that most of the effort in galloping research has been concentrated in bodies with square or rectangular cross-sections, although prismatic bodies with other cross-sectional shapes have been also considered. [4][5][6] In the last years some research on galloping has been carried out at IDR/UPM, and a systematic parametric analysis of simple cross-section two-dimensional bodies has been accomplished (the geometries analysed up to now are isosceles triangular cross-sections, as well as biconvex and rhomboidal cross-sections). In this paper the transverse galloping characteristics of H shaped beams is analysed through static aerodynamic tests, measuring aerodynamic forces on the models.…”