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THE DETERMINATION OF THE LIFT COEFFICIENT IN DESIGNING HYDROFOIL SEACRAFT

A general approach to the determination of design values of the lift coefficient C Sub y for hydrofoil seacraft during non-cavitational operation is discussed. In practice, the problem of determining C Sub y consists of finding the value of its upper limit during non-cavitational operation. Based on the relationship between C Sub y and the foil angle of attack, it is pointed out that in sea swell conditions the actual hydrodynamic angle of attack has to be decreased by the wave rake angle. For modern hydrofoil seacraft with sweptback foils, the foil sweep angle has to be considered and the value of C Sub y has to be corrected by a factor characterizing the decreased sliding effect of arrow-shaped foils. A diagram is presented from which, depending on the absolute and relative foil immersion, maximum values of C Sub y can be determined for a given parameter as a function of the sweep angle and the cruise velocity. It is stated that the maximum permissible C Sub y design values for geometrically similar hydrofoil craft are practically independent of the displacement. At higher speeds, acceptable C Sub y values decrease and the foil sweep increases, thus providing non-cavitational flow. Straight foils with a segmental profile can be used at cruise velocities up to 40--45 knots.

  • Authors:
    • Tikhoplav, OYu
  • Publication Date: 1968

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Filing Info

  • Accession Number: 00014952
  • Record Type: Publication
  • Source Agency: Joint Publications Research Service
  • Files: TRIS
  • Created Date: May 7 1973 12:00AM