A THEORETICAL PREDICTION TECHNIQUE FOR LATERAL HYDRODYNAMIC LOADS ON SIDEWALLS OF SURFACE-EFFECTS SHIPS

A theoretical technique is developed to predict the lateral hydrodynamic forces on low aspect-ratio, parallel, sidewalllike shapes. A free surface is assumed and the effects of cushion pressure and seals are neglected. Two sidewall, flow-field phenomena are modeled in the present technique. They are the mutual interference of the sidewalls in the flow and contributions to the lateral forces and moments of vortices shed from the sidewall bottom edges. A three-dimensional, linear lifting-surface theory is used to predict attached flow, potential pressure distributions that reflect the mutual interference of the sidewalls in the flow field. The bound vorticity distribution is calculated from this pressure distribution and is used in a modified side-edge suction analogy to predict the force contributions due to the vortices shed from the sidewalls. The total hydrodynamic forces are the sum of the potential and the vortex induced loads. Rectangular parallel sidewalls with aspect-ratios of 0.1 and 0.2 are considered. Pressure distributions for different sidewall separation distances at yaw angles from 0 to 20 degrees are presented. Sideforce and yawing-moment coefficients are presented and are compared with experimental data for isolated rectangular wings. The influence of separation distance on the individual sidewall-force coefficients is clearly evident. Comparisons with experiment show reasonable results. The effect on the pressure distribution of a transom is investigated. The present technique predicts realistic pressure distributions for this case, using a simulated separated wake aft of the transom. /Author/

• Corporate Authors:

  David Taylor Naval Ship R&D Center

  Aviation and Surface Effects Department
  Bethesda, MD  United States  20084
• Authors:
  • Whitehead, R E
• Publication Date: 1975-12

Media Info

• Pagination: 43 p.

Subject/Index Terms

• TRT Terms: Aerodynamic lift; Hydrodynamic pressure; Pressure; Surface effect ships
• Uncontrolled Terms: Pressure distribution
• Old TRIS Terms: Hydrodynamic forces; Lifting surface theory
• Subject Areas: Marine Transportation; Vehicles and Equipment;

Filing Info

• Accession Number: 00139424
• Record Type: Publication
• Source Agency: National Technical Information Service
• Report/Paper Numbers: DTNSRDC-4766 Intrm Rpt.
• Files: TRIS
• Created Date: Sep 16 1976 12:00AM