Ankudinov Ship Squat Predictions - Part 1: Theory, Parameters, and FORTRAN Programs

Abstract

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 (ERDC/CHL CHETN-IX-20), further comparisons and validations with laboratory and field measurements are presented and discussed.

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Document Details

Document Type
Technical Report
Publication Date
Aug 01, 2009
Accession Number
ADA508446

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  • Michael J. Briggs

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