Browsing by Author "Craven, A. H."

Now showing 1 - 13 of 13
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    The aerodynamic derivatives of an aerofoil oscillating in an infinite staggered cascade
    (College of Aeronautics, 1960-01) Craven, A. H.
    Thin aerofoil theory is used to obtain, in integral form the aerodynamic derivatives of an aerofoil oscillating in an infinite cascade. The theory allows for arbitrary stagger angle and phase difference between adjacent blades of the cascade. The expressions obtained reduce, for zero stagger and for in phase and antiphase oscillations, to known results.
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    Base pressure at subsonic speeds in the presence of a supersonic jet
    (1960-03) Craven, A. H.
    This paper presents the results of an experimental investigation into the effect of supersonic jets upon the base pressure of a bluff cylinder in a uniform subsonic flow. The ratio of jot diameter to base diameter was 0.1875. Jet stagnation pressures giving slight under-expansion of the jet cause an increase in the base pressure but for larger jet stagnation pressures the base pressure is again reduced. A simple theory, based on a momentum integral, shows the dependence of the base drag upon the jet and free stream speeds and upon the dimensions of the jet and the base.
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    Base pressure at supersonic speeds in the presence of a supersonic jet
    (College of Aeronautics, 1960-12) Craven, A. H.; Chester, D. H.; Graham, B. H.
    The effects on base pressure of jet Mach number, free stream Reynolds number and jet to base diameter ratio have been investigated experimentally. It was found that, for jet stagnation pressures greater than that required for the nozzle to reach its design Mach number, an increase of jet Mach number reduced the base pressure. Similarly the base pressure increased with increase of the ratio of jet diameter to base diameter and, at nigh jet stagnation pressures, base pressures higher than free stream static pressure were found. The base pressurewas independent of frek: stream Reynolds numbers greater than 2 x 10[to the power of 6] per foot but increased with reduction of Reynolds number below 2 x 10[to the power of 6] per foot. Unsteady wave patterns were found when the jet Mach number did not differ markedly from the free stream Mach number and the jet had just reached its design conditions.
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    Boundary layers with suction and injection a review of published work on skin friction
    (College of Aeronautics, 1960-09) Craven, A. H.
    Available data on the effects of suction and injection on skin friction are summarised and compared. It is shown that injection into a turbulent boundary layer can produce a skin friction coefficient lower than the laminar value at trio same Reynolds number on an impermeable plate.
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    The compressible laminar boundary layer with foreign gas injection
    (College of Aeronautics, 1962-01) Craven, A. H.
    The equations of the steady compressible two-dimensional laminar boundary layer with foreign gas injection through a porous wall are solved, using an extended form of Lighthill's approximate method, for arbitrary main stream pressure gradient, wall temperature and injection velocity. The wall shear stress and heat transfer rate are obtained in the form of equations suitable for iteration. It is shown that substantial reductions in skin friction and heat transfer rate can be obtained by the injection of a light gas instead of air.
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    The effect of density on jet flow at subsonic speeds
    (College of Aeronautics, 1959-07) Craven, A. H.
    On the assumption that the velocity and density distributions across a jet of one gas issuing into a stream of a second gas are of exponential form, the momentum integral approach has been employed to find the variation of centre-line velocity downstream of the potential core. The results for the particular case of a jet issuing into a gas at rest are equivalent to those found theoretically by Blottner (Ref. 2) and experimentally by Keagy and Weller (Ref. 1). The results for the jet issuing into a moving stream agree with the limited experiments of the present author. These calculations show the importance of jet to free-stream density ratio with respect to the rate of decay of the jet downstream of the mixing region.
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    The effect of jet deflection on the interference of a rearward facing jet
    (College of Aeronautics, 1957-10) Craven, A. H.
    This paper contains the results of an experimental investigation into the effects induced by a deflected jet upon the body from which it issues. The tests were performed at a Reynolds number of 0.3 x 10(6) based on body diameter and maximum tunnel velocity. It was found that a side force and moment were induced upon the afterbody, the magnitude of which increased with jet deflection and jet thrust. The direction of the induced side force was in a direction opposite to the normal component of the thrust vector. The base drag increased with jet thrust but decreased with increase of jet deflection for small deflections.
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    The flexure-torsion flutter of cambered aerofoils in cascade
    (College of Aeronautics, Cranfield., 1955-12) Craven, A. H.
    This report contains the results of a series of tests on the flexure-torsion flutter of cascades of aerofoils of 30° and 45° camber. The critical flutter speeds and frequencies in cascade are expressed as ratios of the values for the aerofoil in the isolated condition, The tests cover stagger angles between -30° and +30° and gap chord ratios up to 1.5 at a Reynolds number of 1 x 10 to the power of 5 based on aerofoil chord.
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    The free streamline method applied to the flow at the rear of a duct
    (College of Aeronautics, Cranfield, 1956-03) Craven, A. H.
    The free streamline technique is extended to the problem of two-dimensional jet flow from the rear of a nacelle. Complex potentials for the jet flow and the flow in the free stream are found and from these the equation of the wake streamline and the velocity and pressure distributions are calculated. some consideration is also given to the corresponding axi-symmetric problem.
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    The interference of a rearward facing jet on the flow over three representative afterbody shapes in a uniform subsonic flow
    (College of Aeronautics, 1957-04) Craven, A. H.
    This report contains the results of an experimental investigation into the interference of a ,rearward facing undeflected jet on the flow over three afterbody shapes at subsonic speeds. The tests were performed at a Reynolds number of 0.3 x 10(6) based on body diameter. It was found that the form (or pressure) drag coefficient of the bluff afterbody of a right cylinder increased appreciably with increase in jet thrust coefficient. A similar but much smaller increase in form drag was found on an ellipsoidal afterbody and a 'boat-tail'. The effect of the jet was found to extend to approximately three body diameters upstream of the jet exit but that beyond one body diameter the effect was very small.
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    An investigation of vortex breakdown at Mach 2
    (College of Aeronautics, 1963-11) Craven, A. H.; Alexander, A. J.
    Wind tunnel tests have been made at M = 2 on a 75° swept delta wing in order to study the progressive breakdown of the leading edge vortices, which occurs at high incidence. The incidence at which vortex breakdown occurred at supersonic speeds was somewhat less than at low speeds, but the pattern of breakdown appeared to be similar, although the spiralling region of flow is much larger at supersonic speeds. Quite slender objects placed downstream of the wing had appreciable upstream effects, causing vortex breakdown to move upstream by as much as 20% of the root chord for the same incidence.
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    On the application of boundary layer control to a slender wing supersonic airliner cruising at M = 2.2
    (College of Aeronautics, 1962-04) Craven, A. H.; Hopkins, H. L.
    The use of suction or injection to reduce the drag of a supersonic airliner is considered. It is shown that injection gives no reduction in operating costs. With suction applied to an M =2.2 aircraft on the London - New York route, the basic operating cost of 13.30d per short ton statute mile is expected to be reduced by 0.5d for the same payload assuming no change in configuration. If the theoretical maximum skin friction reduction could be obtained the payload could be increased by 4750 lb. and the direct operating cost could be reduced to 10.63d per short ton statute mile.
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    A potential flow model for the flow about a nacelle with jet
    (College of Aeronautics, Cranfield., 1956-03) Craven, A. H.
    The inviscid incompressible flow round a thin nacelle from which a jet is issuing is considered. It is shown that the inhomogeneous motion which may be represented by two semi-infinite distributions of vortices in the two-dimensional case and by a semi-infinite distribution of circular vortex rings in the axi= symmetric case. ...