Browsing by Author "Boyd, E. A."

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    Aerodynamic characteristics of a hypersonic parachute
    (College of Aeronautics, 1961-11) Boyd, E. A.
    Newtonian theory, both in the form of the Modified-Newtonian and the Newton- Busemann pressure laws, is used to find the shape, cloth area and drag of the axisymmetric canopy of a hypersonic parachute, whose only load-carrying fibres are longitudinal ones. As an example, an estimate is made of the size of canopy needed to give a drag of 20,000 lb. in flight at a Mach number of 10 at 100,000 feet altitude.
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    Busemann correction to the characteristics of the two-dimensional hypersonic sail
    (College of Aeronautics, 1960-11) Boyd, E. A.
    The two-dimensional hypersonic sail is examined using the Newton- Busemann pressure law. The results are compared with those of Daskin and Feldman (1958) who used the empirical modified Newtonian pressure law. It is found that for a given chord length of sail a corrected sail will give a specified lift for a smaller tension in the sail. At a flight Mach number of 10 at 100,000 ft. the tension in one particular sail considered could be supported with a working stress of about 20 tons/in[squared].
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    The characteristics of a two-dimensional supersonic sail
    (College of Aeronautics, 1960-12) Boyd, E. A.
    The two-dimensional supersonic sail is analysed using Busemann's second-order theory. It is found to have a universal shape, which is part of a Sici spiral. Aerodynamic characteristics are calculated for a few sails. The tension in sails flying at Mach numbers of 2 and 3 at altitudes of 20,000 and 70,000 feet is large and suggests that wire sails will be needed for flight under these conditions.
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    Ground effect on a rotor wake.
    (Cranfield University, 1985-03) Kusmarwanto, I.; Boyd, E. A.
    The effect of the ground on a rotor wake in forward flight has been investigated experimentally in the working section of an 8ft x Oft straight-through wind tunnel. A three bladed fully articulated rotor with a solidity ratio of 0.07 and diameter of 1.06m, powered by a hydraulic motor, has been tested at a height of 0.47 rotor diameter above a solid ground board which has an elliptical leading edge. Tests have been run at various low advance ratios (<0.1) with two collective pitch settings. A three-element hot wire anemometer probe has been used to measure the average value of the three components of velocity simultaneously in the forward half (advancing side) of the rotor wake and in the main stream surrounding it. The rotor wake and the ground vortices have been visualized by smoke. Surface flow patterns on the ground board have located the interaction region between the rotor wake and the oncoming flow on the ground board. Theoretical estimates of the flowfield based on Heyson's vortex cylinder model (Ref. 2) are compared with the experimental results. Both experimental results and theoretical estimates show that the ground-induced interference is an upwash and a decrease in forward velocity. The upwash interference' opposes the vertical flow through the rotor, and have large effects on the rotor performance in producing thrust. The streamwise interference decelerates the mainstream and becomes more noticeable as the wake boundary is approached.
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    Slender shapes offering minimum drag in free-molecular flow
    (College of Aeronautics, 1965-09) Boyd, E. A.
    Analytical expressions are obtained for the optimum shapes which minimise the drag of a slender axisymmetric body in free-molecular flow, provided the drag expression is simplified using the slenderness assumption. The problem is formulated as one of Mayer type in the calculus of variations and solved by using the Buler-Lagrange equations together with the transversality condition. The shapes derived are optimum subject to constraints on thickness, length, wetted area and volume. In the particular cases solved any two of these four quantities are fixed while the remaining two are free. The expression for the shape of the body when thickness is free is obtained in closed form.