122 research outputs found

    Hydrodynamic Performance of a Surfboard Fin

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    The performance of a generic surfboard fin is investigated in a cavitation tunnel to gain basic understanding of the viscous flows involved for future systematic experimental and computational studies. Measurements of lift and drag forces, pitching moment and results of flow visualisation are presented. Surface flow visualisation studies reveal relatively complex boundary layer transition and separation phenomena although lift and drag characteristics are virtually invariant with Reynolds number in the range tested. A mixed two- and three-dimensional separation behaviour is observed at high incidence

    Limitations on 2D Super-cavitating Hydrofoil Performance

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    Classical super-cavitating hydrofoil performance predictions have been based on linearised potential theory for zero cavitation number. More rationalised predictions of super-cavitating hydrofoil performance have been evaluated using a non-linear boundary element formulation. Comparisons are made between flat-plate, circular-arc, and NACA 4-digit camber line wetted surface profiles. Limitations of super-cavitating foil performance are defined in terms of minimum cavity length to avoid instability and the minimum cavity clearance from the hydrofoil wetted surface. The dependence of these limitations on hydrofoil wetted surface profile, incidence and cavitation number are derived

    Development of a Fast Response Pressure Probe for Use in a Cavitation Tunnel

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    The performance of a prototype fast response probe designed for use in a cavitation tunnel is investigated. The probe consists of a total head tube with an embedded miniature pressure sensor. Miniaturisation allows installation of the pressure transducer close to the head of the head of the instrument and improves frequency response through reducing inertia of fluid in the connecting tube. Measurements made with the fast response probe are compared with those of a Pitot tube connected to a slow response transducer and a hot film probe in a thickened turbulent boundary layer on the tunnel ceiling. Measurements of both streamwise velocity and turbulence made with the probe were found to compare well with those of a Pitot tube and a hot film probe. A useful frequency response up to 2.5kHz in water was demonstrated without any frequency compensation for pressure tube response
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