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Browsing by Author "Foerster, K. E."

Now showing 1 - 6 of 6
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    Force Characteristics of Restrained, Naturally Ventilated Hydrofoils in Regular Waves
    (St. Anthony Falls Hydraulic Laboratory, 1965-03) Foerster, K. E.
    Earlier measurements of steady flow force characteristics of forced ventilated hydrofoils with trailing edge flaps have been supplemented with additional measurements using naturally ventilated hydrofoils. These measurements have been compared with a few theoretical points based on the non-linear theory of Wu and Wang for two-dimensional foils at non-zero cavitation number. The theory was also modified using Cumberbatch's method to include effects of finite span. Good agreement between the theory and experimental data Was obtained. Measurements were also made of the oscillatory lift and drag forces for restrained, naturally ventilated foils of finite span moving through a regular wave train. Flat plate foils with aspect ratios of 2 and 3 were used. The experimental data for the forces agreed fairly well with calculations based on the instantaneous angle of attack and cavitation number, and the reduced force coefficients indicated little variation with reduced frequency, νc/V, up to about 1.1. The phase angle between the maximum lift force and the wave crest increased with increasing reduced frequency. Computations for the phase angle based on quasi-steady assumptions were valid only at low reduced frequencies. Cavity wash-off was found to occur due to wave-induced changes in the angle of attack. The angle at which wash-off occurred was related to the wave characteristics for low aspect ratio foils. For a foil with an aspect ratio of 4, cavity wash-off generally occurred at the same angle of attack as that required to maintain a cavity in smooth water.
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    Further Experiments on a Jet Flap Hydrofoil in Ventilated Flow
    (St. Anthony Falls Laboratory, 1967-12) Wetzel, J. M.; Foerster, K. E.
    Experimental measurements were made of the force characteristics of a naturally ventilated hydrofoil of finite span submerged below a free surface and equipped with a jet flap. Jet momentum coefficients up to 0.35 were attained. The increment of lift associated with action of the jet flap was primarily dependent on the jet momentum coefficient and the flap angle. Measured lift increments were considerably less than those calculated by Ho from linearized theory for two-dimensional foils and zero cavitation number. Thrust recovery was dependent on the jet momentum coefficient and the flap angle, decreasing as these parameters were increased. In. all cases thrust recovery was greater than the horizontal component of the jet reaction. A brief series of tests was also conducted with a restrained, jet flap foil moving through a regular wave train. For reduced frequencies, based on the full chord, up to 0.7, the oscillatory force characteristics were essentially the same as for the foil without the jet flap for otherwise identical conditions.
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    Measurements of the Leading-Edge Separation Bubble for Sharp-Edged Hydrofoil Profiles
    (ST. ANTHONY FALLS HYDRAULIC LABORATORY, 1966-06) Wetzel, Joseph M.; Foerster, K. E.
    Measurements were made of the length of the leading edge separation bubble for sharp-edged profiles of finite span submerged below a free surface. These hydrofoils were tested under a fully-wetted flow condition. Flow visualization techniques were used to determine the separation region primarily as a function of velocity, chord length, profile shape, aspect ratio, and angle of attack. The bubble length increased with increasing angle of attack and aspect ratio. An increase in the wedge angle for wedged shaped profiles required an increase in angle of attack to attain the same bubble length. Variation of the chord length and leading-edge thickness had little effect on the ratio of bubble to chord length.
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    Model Study of the Spillway of the Reza Shah Kabir Project Khuzestan Water and Power Authority Ministry of Water and Power - Government of Iran
    (St. Anthony Falls Hydraulic Laboratory, 1969-05) Foerster, K. E.; Anderson, Alvin G.
    A model of the spillway for the Reza Shah Kabir Project of the Khuzestan Water and Power Authority of the Government of Iran on the Karun River was constructed at a scale of 1:78.7 and tested at the St. Anthony Falls Hydraulic Laboratory of the University of Minnesota. The purpose of the test was to examine the nature of the flow in the spillway and tailrace and to provide data for the structural design.
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    Studies of the Flow Characteristics of a Compressible, Bubbly Mixture about Supercavitating Bodies and in a Converging-Diverging Nozzle
    (St. Anthony Falls Hydraulic Laboratory, 1964-04) Schiebe, F. R.; Wetzel, J. M.; Foerster, K. E.
    Experimental studies have been made to determine the effect of a compressible, air-water mixture on the drag characteristics of a cavitating body. Data are reported for a series of conical bodies of various slenderness ratios for free stream Mach numbers up to 0.7. Results indicate that the drag coefficient increases with Mach number, although in general not as rapidly as for a non-cavitating body. It was possible to apply Gothert's rule to adequately predict the drag coefficient up to Mach numbers of about 0.6. A brief study was also conducted to study the flow characteristics of an air-water mixture in a converging-diverging nozzle. Supersonic flow was obtained and shock waves were observed downstream of the throat. Measured throat pressures for choked flow were somewhat higher than those calculated from homogeneous mixture theory.
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    Unsteady Force and Cavity Characteristics for Ventilated Hydrofoils
    (St. Anthony Falls Laboratory, 1967-06) Wetzel, Joseph M.; Foerster, K. E.
    Experimental measurements were made of the unsteady cavity and force characteristics for both forced and naturally ventilated hydrofoils of finite span submerged below a free surface. Unsteady cavity characteristics were studied for a force-ventilated wedge subjected to a sudden change in either the .air flow rate to the cavity or angle of attack. Differences were observed in air entrainment rates measured for the unsteady case as compared to the corresponding instantaneous steady case. The magnitude of the differences depended on the kind of unsteadyness introduced. Unsteady force characteristics were determined for naturally ventilated foils undergoing either a sinusoidal heaving motion or a harmonic oscillation of a trailing edge flap. The amplitude of the oscillatory lift was found to increase with increasing reduced frequency for a heaving foil, whereas the oscillatory lift was essentially constant up to reduced frequencies of 1.2 for the foil with an oscillating flap. There is limited agreement of the data with available theory.