Vortex Lattice Method for a Straight Hydrofoil Near a Free Surface

Article type: Research Article

Authors: Thiart, G.D.

Affiliations: Department of Mechanical Engineering, University of Stellenbosch, South Africa

Abstract: The paper presents a vortex lattice method for the calculation of lift on a straight hydrofoil of finite span near the free surface of an infinitely deep fluid. The velocity field induced by the vortex lattice satisfies the linearized free surface boundary condition and the radiation condition. Lift calculations are compared with experimental results for a 5.11 aspect ratio hydrofoil of the circular arc type. Two options regarding the path of the trailing vortices are examined, i.e. that the trailing vortices leave the hydrofoil directly from the camber surface or via the trailing edge. It is shown that for moderate effective angles of attack the results are very similar, and that the first option, which is simpler and computationally more efficient than the second, is sufficiently accurate for practical purposes. The method was also used to compute the variation of hydrodynamic characteristics with depth of submergence and Froude number for a flat plate of finite span. Results are presented for aspect ratios of 2, 5 and 10 respectively.

DOI: 10.3233/ISP-1997-4443701

Journal: International Shipbuilding Progress, vol. 44, no. 437, pp. 5-26, 1997