Abstract

A series of OSISTHI (Ocean Structure Interaction Simulator - Ice-Hull Interaction) simulations is conducted in support of the subsequent USCGC Mackinaw model test and to explain the maneuvering behavior observed of the USCGC Polar Icebreaker indicative design previously tested. This and the accompanied paper document the result of these simulations. The accompanied paper focuses on validation and calibration of the numerical model; while, this paper presents the correlation between simulation and model test results.

Introduction

A series of OSISTHI (Ocean Structure Interaction Simulator - Ice-Hull Interaction) simulations were conducted to support the Mackinaw model test by providing numerical evidence to explain the observed maneuvering behavior of the indicative design. The accompanied paper (Lau, 2021a) focuses on validation and calibration of the numerical model; while, this paper presents the correlation between simulation and model test results. Lau (2021b) further explores effects of hull geometry and tightness of turns on ship maneuverability as part of this work. For background, scope and objectives of this work, as well as the validation and calibration of the numerical model, please refer to Lau (2021a).

Simulation of Mackinaw in Model Test Condition

The manager of the Mackinaw model test project identified representative sea-trial runs for a case-by-case modeling in OCRE-RC's ice basin. These include three runs in 0.493 m freshwater ice conducted on March 5, 2007 and two runs in 0.610 m conducted on March 6, 2007. (St. John et al., 2012) OSISTHI simulation of these test cases was then performed to assist in model test preparation and subsequent data validation. Test types simulated included straight ahead and turning circle maneuvering in ice.

Typical to all rectangular ice tanks with limited tank width, a complete 180° turn required for a tactical diameter simulation is rarely done in OCRE-RC; instead, turning arc maneuvers are performed with the ship stopped prior to 90° heading change. The diameter from such arc is assumed to be representative and sometimes reported as tactical diameter. This practice calls into question the validity of the reported value. Hence, a second series of OSISTHI simulations was conducted to examine the validity of such practice by tracking the ship speed, yaw rate and the instantaneous turning diameter for a range of tactical diameters representative of gentle turns made by icebreaking tankers with conventional propeller configurations to the much tighter turns made by podded icebreaking ships.

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