A series of OSIS-IHI simulations is conducted in support of the subsequent USCGC Mackinaw model test and to explain the maneuvering behavior observed from the USCGC Polar Icebreaker indicative design previously tested. This paper focuses on validation and calibration of the numerical model.
The podded version of the United State Coast Guard's (USCG) indicative polar icebreaker design has shown substantially poorer maneuvering performance in comparing to those of the more traditional hull form design (a version equipped with tri-screw conventional propellers) during the USCG model test program in the National Research Council - Ocean, Coastal and River Engineering Research Center's ice basin (Wang et al., 2018). USCG requested a model test on its ice cutter USCG Mackinaw for model-scale/full-scale correlation to gain additional insights into the maneuverability of the indicative design.
Both versions of the USCG indicative polar icebreaker design have identical bow form; however, the traditional hull form has a short parallel mid-section while the podded version extends the parallel mid-section much further aft. It is hypothesized that this extended mid-section will cause a large resisting moment against turning due to increased icebreaking load at the aft part of the mid-section. Results from a preliminary numerical simulation using OSIS-IHI (Ocean Structure Interaction Simulator - Ice-Hull Interaction) gives support to this hypothesis.
OSIS-IHI is a modeling software designed to simulate ship maneuvering in ice and developed for marine simulation and ship performance assessment applications (Lau, 2011). A series of OSIS-IHI simulations were conducted to support the Mackinaw model test by providing numerical evidence to explain the observed maneuvering behavior of the indicative design. It also seizes the opportunity to conduct additional validation of OSIS-IHI as part of a numerical capability development effort. This paper focuses on validation and calibration of the numerical model. The correlation between simulation and model testing results is presented in an accompanied paper (Lau, 2021a); and exploration of the effects of hull geometry and tightness of turns on ship maneuverability are presented elsewhere (Lau, 2021b).
