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Browsing by Author "Maxwell, W. H. C."

Now showing 1 - 3 of 3
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    Force Characteristics of Flapped, Ventilated Hydrofoils in Smooth and Rough Water
    (St. Anthony Falls Hydraulic Laboratory, 1963-01) Wetzel, J. M.; Maxwell, W. H. C.
    Experimental measurements were made of the lift and drag forces on superventilated hydrofoils of finite span submerged below a free surface. The foils were equipped with fixed trailing edge flaps of various angles of deflection. Experimental lift data taken with the foil in smooth water and extrapolated to zero cavitation number agreed well with two-dimensional theory modified to include effects of finite span and submergence. Measurements of the oscillatory forces for an artificially ventilated foil moving through a regular progressive wave train agreed well with quasi-steady calculations for near zero σ. At the higher σ, the calculated values were greater than the measured, primarily through deficiencies in the prediction of the oscillatory cavity pressure.
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    Longitudinal Motions and Stability of Two Hydrofoil Systems Free to Heave and Pitch in Regular Waves
    (St. Anthony Falls Hydraulic Laboratory, 1961-12) Wetzel, J. M.; Maxwell, W. H. C.
    Experimental measurements were made of the motions of two hydrofoil configurations free to heave and pitch in regular waves. The two configurations consisted of 1) a dihedral (V) foil forward, flat foil aft, and 2) dihedral (V) foils both fore and aft, and a flat foil near the center of gravity. The motions were measured in both head and following seas for a variety of wave characteristics and two towing velocities. The experimental results were compared with quasi-steady linear and nonlinear theory, and also unsteady linear theory. In general, agreement with the quasi-steady linear theory was satisfactory, although some improvement in the correlation was obtained by considering the effects of unsteadiness. Nonlinearities had little effect on the amplitudes of the oscillatory motions. The major effect of the nonlinearities was to produce a steady downward component of heave. The measured component was in most cases greater than that derived from analog computer solutions of the nonlinear equations. Experimental investigation of the inherent stability of both configurations in smooth water indicated that the damping was greater than predicted by the quasi-steady linear theory.
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    Tandem Interference Effects of Flat Noncavitating Hydrofoils
    (St. Anthony Falls Hydraulic Laboratory, 1962-05) Wetzel, J. M.; Maxwell, W. H. C.
    Experimental measurements were made of the interference effect of two submerged, flat, noncavitating hydrofoils of finite span in tandem. the surface wave generated by a single foil was measured in the longitudinal and lateral directions. Downwash angles were determined from the experimental data for various foil separations and submergences. Comparison of the results with theory was favorable. Limited measurements were also made of the oscillatory lift and dag forces for a foil moving through a progressive wave train. The data agreed with quasi-steady theory for the lower frequencies of encounter. At the higher frequencies of encounter, consideration of unsteadiness effects improved the correlation.