A NEW METHOD FOR SOLVING SURFACE-PIERCING-STRUT PROBLEMS
The problem of a potential flow around a surface-piercing strut at a high Froude number is proposed. The strut can be of asymmetric cross-section and is not necessarily slender. The exact boundary-value problem is formulated and is approximated by a mathematical model which satisfies the linearized free-surface boundary conditions on the undisturbed free-surface and the rigid-body boundary condition on the actual surface of the strut. It is found that the problem can be broken into two parts, one of which is a conventional infinitie-fluid problem, the other a problem which can be formulated as a two-dimensional unsteady-flow problem. A numerical scheme is developed and applied for three cases, namely, aspect ratios of 0.5, 1.0 and 3.0. The cross-section of the strut is a lens shape, the thickness/length ratio of which is 0.1. Side-force coefficients and wave patterns are calculated for various Froude number. The side-force coefficient calculated for 0.5 aspect ratio shows good agreement with the experimental result for a flat plate of the same aspect ratio and angle of attack. The side-force coefficient for aspect ratios 1.0 and 3.0 is shown to change with respect to Froude number in a pattern similar to that for aspect ratio 0.5. Also, it is shown to approach the analytical limit values as the Froude number increases. The results calculated predict a significant change of the wave pattern on the suction side of the strut as the aspect ratio changes. The presnt method can be applied for prediction of the bow waves. The numerical calculation is performed for a double-wedge-shaped model used by Standing (1974). The calculated bow wave pattern shows good agreement with the corresponding experimental result.
- This research was carried out under the Naval Sea Systems Command General Hydromechanics Research Program subproject SR 023 01 01, administered by David W. Taylor Naval Ship Research and Development Center.
University of Michigan, Ann ArborDepartment of Naval Architects and Marine Engineers
Ann Arbor, MI United States 48109
- Kaiho, T
- Publication Date: 1978-2
- Pagination: 54 p.
- Issue Number: 196
- TRT Terms: Bow waves; Free surface; Froude number; Hydrodynamic pressure; Hydrofoil boats; Potential flow; Struts; Thinness; Two dimensional flow; Vehicle design
- Uncontrolled Terms: Ship design
- Old TRIS Terms: Effects; Free surface effects; Hydrodynamic forces; Slender bodies
- Subject Areas: Design; Marine Transportation;
- Accession Number: 00184794
- Record Type: Publication
- Source Agency: National Technical Information Service
- Report/Paper Numbers: Intrm Rpt.
- Contract Numbers: N00014-75-C-0366
- Files: TRIS
- Created Date: Jan 13 2004 12:00AM