A NUMERICAL METHOD FOR THE SOLUTION OF THE UNSTEADY LIFTING PROBLEM OF RECTANGULAR AND ELLIPTIC HYDROFOILS

A numerical method for the solution of the unsteady lifting problem is developed. Linearized boundary value problem is formulated for the hydrofoil which is situated in the unbounded incompressible inviscid fluid, oscillating in either heave or pitch mode in the free stream flow. The discrete vortex method is used to represent the physical model and the downwash integral is reduced to a set of simultaneous algebraic equations, that is solved by a step-by-step procedure in time. Sample calculations are performed for rectangular and elliptic hydrofoils up to a reduced frequency of about 2.0 showing a good agreement with the earlier works up to a reduced frequency of 1.0. It is also shown that the method may be applicable to the lifting surfaces of more general shape with non-straight trailing edge. Convergence to the steady oscillating response is obatined after about 1 1/2 cycles of calculations for the oscillations with zero mean angle of attack, but Wagner's effect is observed for the oscillations with non-zero mean angle of attack which requires at least nine chordlengths of wake to ensure the sufficiently steady response.

  • Corporate Authors:

    Massachusetts Institute of Technology

    Sea Grant Program, 77 Massachusetts Avenue
    Cambridge, MA  USA  02139
  • Authors:
    • LEE, C S
  • Publication Date: 1977-1

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Filing Info

  • Accession Number: 00159503
  • Record Type: Publication
  • Source Agency: Massachusetts Institute of Technology
  • Report/Paper Numbers: MS Thesis
  • Files: TRIS
  • Created Date: Aug 31 1977 12:00AM