Showing papers by "Vaughn College of Aeronautics and Technology published in 1989"
TL;DR: In this article, a number of stochastic models of fatigue crack growth under constant amplitude cyclic loading are assessed in the light of experimental data, and the predictive performance of the models under a change in the initial crack length is found to provide a poor estimate of the standard deviation of the number of cycles to failure.
12 citations
TL;DR: In this article, a full-scale solid model of the X-RAE1 was tested in the Royal Aerospace Establishment 7.3 m tunnel and a new wing of the Wortmann FX63-137 airfoil was then retested with a new Wortman section, which gave substantial gains in CLmax and L/D ratio.
Abstract: Seven airfoil sections suitable for remotely piloted vehicles (RPV's) were tested at full-scale Reynolds numbers in the College of Aeronautics low-speed wind tunnel. The pressure distributions and force measurements were used to validate the mathematical model proposed by Williams. Three of the airfoils were further tested with roughness added. Of the airfoils tried, the Wortman FX63-137 had the best performance. It was therefore decided to retrofit a wing of this section to an RPV designated X-RAE1. The original wing for this RPV had an unspecified flat-bottomed section, with a maximum thickness/chord ratio of 14.1% at the 30% chord station. First, a full-scale solid model of the X-RAE1 was tested in the Royal Aerospace Establishment 7.3 m tunnel. It was then retested with a new wing of the FX63-137 section, which gave substantial gains in CLmax and L/D ratio. Finally, a fully instrumented version of the X-RAE1 was constructed. Flight trials with the standard (flat lower surface) wing and with a new wing of the Wortmann section confirmed the superiority of the FX63-137 airfoil. However, the flight tests also showed the large drag penalties due to the many practical features of a real flying vehicle.
11 citations
TL;DR: In this paper, the effect of trailing edge extensions was tested for the Gottingen 797 and Wortmann FX 63-137 aerofoil sections with smooth surfaces at chord Reynolds numbers from 3 x 10 5 to 1 x 10 6 in the 8ft x 6ft low speed wind-tunnel at the Cranfield Institute of Technology.
Abstract: The effect of trailing edge extensions was tested for the twodimensional Gottingen 797 and Wortmann FX 63-137 aerofoil sections with smooth surfaces at chord Reynolds numbers from 3 x 10 5 to 1 x 10 6 in the 8ft x 6ft low speed wind-tunnel at the Cranfield Institute of Technology. Force measurements were made on the basic aerofoil sections and with extension plates of 10% and 20% chord set tangential to the upper surface at the trailing edge. It was verified that the addition of an extension plate effectively brings about an increase of maximum lift coefficient and an improved lift-to-drag ratio for the Gottingen aerofoil section. However, the effect of the extension plate was small on the Wortmann aerofoil section.
1 citations
TL;DR: In this paper, pressure distributions over a 6:1 fineness ratio ogive cylinder model have been obtained over a wide pitch range in the rectilinear flow provided by the CoA 8 ft x 6 ft low speed wind tunnel and the curvilinear motion provided by CoA Whirling Arm facility.
Abstract: The pressure distributions over a 6:1 fineness ratio ogive cylinder model have been obtained over a wide pitch range in the rectilinear flow provided by the CoA 8 ft x 6 ft low speed wind tunnel and the curvilinear motion provided by the CoA Whirling Arm facility. The pressure distributions were integrated first to obtain the local normal-force loading distribution along the body and then the overall normal-force and pitching moment and hence the centre of normal-force. A comparison of the results showed that the main difference between the aerodynamic characteristics was a considerable positive increase in normal-force loading over the whole of the afterbody in curvilinear motion which varied little with the magnitude or sign of the pitch angle. Some smaller changes were also apparent in the forebody loading characteristics. These changes resulted in the body developing considerably more normal-force and nose-down pitching moment in curvilinear motion than in rectilinear flow with the resultant large rearward movement of the centre of normalforce. It was found possible to estimate the main features of the loadings, but the theoretical methods available did not predict very well the variations in loading obtained experimentally at the extreme beginning and end of the parallel afterbody.