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October 2013 www.sname.org/sname/mt (abstracts )SNAME Paper Abstracts Comparison of Measured Ship Squat with Numerical and Empirical Methods BY MICHAEL J. BRIGGS, PAUL J. KOPP, VLADIMIR K. ANKUDINOV, AND ANDREW L. SILVER PUBLISHED IN THE JUNE JOURNAL OF SHIP RESEARCHe Beck, Newman and Tuck (BNT) numer- ical predictions are used in the Coastal and Hydraulics Laboratory (CHL) Channel Analysis and Design Evaluation Tool (CADET) model for predicting underkeel clearance (UKC) resulting from ship motions and squat. The Ankudinov empirical squat prediction formula has been used in the CHL ship simulator and was recently updated. e World Association for Waterborne Transport Infrastructure (for- merly e Permanent International Association of Navigation Congresses, PIANC) has recom- mended several empirical and physics-based formulas for the prediction of ship squat. Some of the most widely used formulas include those of Barrass, Eryuzlu, Huuska, ICORELS, Römisch, Tuck, and Yoshimura. e purpose of this article is to compare BNT, Ankudinov, and PIANC predictions with measured DGPS squat data from the Panama Canal for four ships. ese comparisons demonstrate that the BNT, Ankudinov, and PIANC predictions fall within the range of squat measurements and can be used with condence in deep draft channel design. Planing in Shallow Water at Critical Speed BY MICHAEL G. MORABITO PUBLISHED IN THE JUNE JOURNAL OF SHIP RESEARCHThis article summarizes experiments to determine the eect of shallow water on at- bottomed prismatic hulls towed xed in heave and trim over a wide range of speed regimes. e experimental design allowed for the sepa- rate measurement of pressure forces normal to the bottom and viscous forces tangential to the bottom. e experiments showed that below a depth Froude number of unity (subcritical speeds), shallow water resulted in a reduc- tion in pressure forces on the bottom of the hull. Around a depth Froude number of unity (critical speed), a solitary wave formed at the model, increasing the wetted length and also increasing the bottom pressure forces, which became unsteady. Above a depth Froude num- ber of unity (supercritical speeds), the pressure forces on the bottom of the hull were greater in shallow water than in deep water. Observations of the inception of transom ventilation showed that full ventilation occurred at lower Froude numbers in shallow water and that trim has a strong eect on transom ventilation at all water depths. To assist in explaining these eects, each of the forces acting on a at-bottomed hull are discussed and it is shown how they vary with speed and water depth. e observed trends from these xed model tests are in quali- tative agreement with experiments with free to trim and heave models as well as two-dimen- sional theories of planing in shallow water. Block Erection Sequencing in Shipbuilding With General Lifting and Joining Times BY HENRI TOKOLA, ESKO NIEMI, AND HEIKKI REMES PUBLISHED IN THE MAY JOURNAL OF SHIP PRODUCTION AND DESIGNis article studies the scheduling of block erec- tion in shipbuilding. A mathematical model is formulated to minimize the makespan, i.e., the time between the start and nish of the erec- tion schedule, when there are dierent lifting and block joining times. Structural stability and the no-skipped-blocks property are taken as constraints. e model is used to study the erection in three special cases. First, the case with a short lifting time is analyzed. Second, a solution is constructed for the case in which joining times are short and, third, the case in which the lifting and joining times are the same is analyzed. e article shows how these three cases can be solved eciently, and, in addi- tion, it gives insight into the erection scheduling such as the eects of the number of blocks in the horizontal and vertical directions on dier- ent joining times. Scaling of Resistance From Surface-Eect Ship Model Tests BY CHRIS B. MCKESSON AND LAWRENCE J. DOCTORS PUBLISHED IN THE MAY JOURNAL OF SHIP PRODUCTION AND DESIGNIn the case of conventional (displacement) hulls, model testing is based on the assump- tion (with or without certain renements) that the total resistance can be expressed as: where R T is measured in the towing tank, and the frictional resistance, R F, can be accurately estimated by the application of a friction line and the use of the calm-water wetted surface. It is assumed that the dimensionless residu- ary resistance R R is the same for the model and the prototype vessel. Our article may be considered to be an extension of the classic article by Wilson, Wells, and Heber (1978) to the more complex case of the surface-eect ship, as follows. Specically, we opine that: Here, R W is the wave resistance of the vessel (caused by a combination of the actions of the cushion pressure and the two sidehulls), RH is the transom (hydrostatic) drag, R S is the seal drag, R M is the momentum drag, and RSPRAY is the spray drag. R T is the only one of these quantities that is measured during the model test. e other components require the use of a variety of estimates. In the article, we present specic examples of our approach as applied to a number of tests on surface- eect ship models that we have studied in recent years. Numerical Modeling of a Planing Hull Maneuvering in a Regular Wave, Part 1: Dynamic Instability BY RAY-QING LIN AND TIM SMITH PUBLISHED IN THE MAY JOURNAL OF SHIP PRODUCTION AND DESIGNe surf rescue boat (SRB) of the United States Coast Guard is a class of high-speed planing Editors note: The following are abstracts of papers recently presented at SNAME events and/or published in SNAME publications. The papers can be found at www. sname.org/sname/mt/featuredabstracts View current and previous issues of Journal of Ship Production and Design and Journal of Ship Research at http://www.sname.org/SNAME/Pubs/Journals1/