ON {BLOCKAGE CORRECTION AND EXTRAPOLATION TO SMOOTH {SHIP RESISTANCE

A new expression for blockage correction of ship model resistance, at Froude numbers up to 0.25, involving variation with Reynolds number and a form factor, is derived semi-empirically. After its use, data from eight towing tanks for geosim series of seven different forms without bulbous bows are analyzed using a new expression of viscous resistance coefficient given (in thousandths) by 8.6 x plus K (x squared), in which x = (log(10) Rn-4) to the power -1 and k is a form factor found from resistance measurements at low Froude number. This expression fits model data without bias and, unlike any other extrapolator, provides an estimate of the hydraulically smooth Lucy Ashton which is quantitatively consistent with the actual ship data. Use of an expression of k in terms of block coefficient, length/displacement ratio, and U-ness of stern is shown to be potentially capable of estimating smooth ship resistances to within plus or minus 3 percent for forms with bulbous bows as well as for forms without.

• Supplemental Notes:
  • Presented at the SNAME Annual Meeting, Nov 12, 1970.
• Corporate Authors:

  Society of Naval Architects and Marine Engineers

  601 Pavonia Avenue
  Jersey City, NJ  United States  07306-2907
• Authors:
  • Scott, J R
• Publication Date: 1970

Media Info

• Features: Appendices; Figures; References; Tables;
• Pagination: 31 p.
• Serial:
  • Issue Number: 7

Subject/Index Terms

• TRT Terms: Fluid resistance; Ship motion; Ships; Structural models
• Uncontrolled Terms: Ship models
• Subject Areas: Bridges and other structures; Design; Marine Transportation; Vehicles and Equipment;

Filing Info

• Accession Number: 00007486
• Record Type: Publication
• Files: TRIS
• Created Date: Dec 22 1973 12:00AM