Ankudinov Ship Squat Predictions - Part 1: Theory, Parameters, and FORTRAN Programs
ENGINEER RESEARCH AND DEVELOPMENT CENTER VICKSBURG MS COASTAL AND HYDRAULICS LAB
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Squat is the reduction in underkeel clearance UKC between a vessel at-rest and underway due to the increased flow of water past the moving hull. The forward motion of the ship pushes water ahead of it that must return around the sides and under the keel. This water motion induces a relative velocity between the ship and the surrounding water that causes a water level depression in which the ship sinks. The velocity field produces a hydrodynamic pressure change along the ship similar to the Bernoulli effect. This phenomenon produces a downward vertical force sinkage, positive downward and a moment about the transverse axis trim, positive bow up that can result in different values of squat at the bow and stern . This combination of sinkage and change in trim is called ship squat. This Coastal and Hydraulics Engineering Technical Note CHETN summarizes the Ankudinov empirical formula for ship squat predictions used by the U.S. Army Engineer Research and Development Center ERDC Ship Tow Simulator STS. This CHETN documents the Ankudinov squat formulas and describes two FORTRAN programs that were written for single and multiple ship speed applications. Two examples are given for a Panamax bulk carrier and Panamax tanker for both programs. A companion CHETN compares and validates the Ankudinov squat predictions with laboratory measurements of a Post-Panamax containership and field measurements of a Panamax containership, tanker, and bulk carrier in the Panama Canal. It also compares the Ankudinov formula with several of the Permanent International Association of Navigation Congresses PIANC empirical squat formulas. In Part II of this CHETN ERDCCHL CHETN-IX-20, further comparisons and validations with laboratory and field measurements are presented and discussed.
- Computer Programming and Software
- Fluid Mechanics