Ice loads acting on a model podded propeller blade (OMAE2005-67416)

With the increase in popularity of podded propulsors and arctic navigation, understanding the interaction between a podded propulsor and ice has become more important. Propeller-ice interaction itself is a complicated process with a high level of uncertainty resulting from the uncertainties associated with the properties of the ice and with the propeller-ice interaction conditions. Model tests provide relatively well-controlled ice properties and interaction conditions to reduce the uncertainties. In order to improve the understanding of this interaction and to develop numerical models of it, a model podded propulsor was used in “Puller” mode, and ice loads were measured on its instrumented blade and propeller shaft. The results of the experiments conducted to simulate the interactions (milling) of the instrumented blade with ice in different operating conditions are reported in this paper. Loads measured during the milling consist of ice milling loads, “inseparable” hydrodynamic loads, and “separable” hydrodynamic loads. The sample results presented here include ice milling and inseparable hydrodynamic loads for various advance coefficients and depths of cut (amount of blade penetration into ice). Some results are compared with existing ice load models

Prediction of propeller performance on a model podded propulsor in ice (propeller-ice interaction)

With the increase in popularity of podded propulsors and arctic navigation, understanding the interaction between a podded propulsor and ice has become more important. Propeller-ice interaction itself is a complicated process resulting from the variations associated with the properties of the ice and with the propeller-ice interaction conditions. Model tests provide relatively well-controlled ice properties and interaction conditions to reduce these variations. -- The objective of this work is to understand propeller-ice interaction phenomena and develop a numerical method to predict the interaction ice loads. A model podded propulsor was tested in an ice tank with scaled model ice. Three six-component dynamometers and six single-axis dynamometers measured the ice loads acting on various positions of the experimental model. In order to achieve the desired numerical simulations, both a Panel method and empirical formulae were used. The Panel method was suitable for predicting the hydrodynamic loads acting on the propeller blades. The empirical formulae for the ice milling loads were also implemented into the Panel method, thus the hydrodynamic loads and ice milling loads were calculated simultaneously. The ice milling loads model takes into account geometric and kinematic considerations. -- Numerical results were compared and validated with the experimental results. The numerical model was valid for the first quadrant operating conditions with various azimuthing (yaw) angles. The numerical results showed a good agreement with experimental results. The findings from this work were then presented and discussed

Model-scale/full-scale correlation of OCRE's model test results in supporting the CCGS Polar Icebreaker model test data evaluation

This document gives a summary of the model-scale/full-scale correlation performed on model test data generated at the National Research Council Ocean, Coastal, and River Engineering (NRC-OCRE) test facility in St. John\u2019s in support of the evaluation of the fullscale prediction from the NRC-OCRE\u2019s CCGS Polar Icebreaker model test result. This correlation includes ship performance predictions, i.e., resistance, propulsion and manoeuvring. The review has shown a good agreement between NRC-OCRE model test predictions and full-scale measurements. Sensitivity analysis of flexural strength on both ice resistance and ship power shows an increase of only 9.7 and 13.7 % of ice resistance and ship power, respectively, even with a 35 % strength increase.Peer reviewed: NoNRC publication: Ye

Implementation, verification and validation of the multi-surface failure envelope for ice in explicit FEA (LS-DYNA) with full derivation of it\u2019s invariant form

The multi-surface failure criterion/model for ice is implemented into an explicit finite element program called LS-DYNA (www.lstc.com). The implementation of the model equations was achieved via the development of a user routine for LS-DYNA. Since ice behavior depends on temperature, strain/load rate and loading direction (loading direction for the case of anisotropic ice), the traditional isotropic and temperature and rate independent failure criterion such as von-Mises and Mohr-Coulomb are not applicable. The multi-surface failure criterion (Derradji-Aouat, 2003) accounts for those effects and is formulated with the parameters of the octahedral shear stress and hydrostatic pressure. In this paper, a 3-step procedure will be presented and discussed to demonstrate successful multi-surface failure model implementation in explicit FEA. Step 1 is concerned with the theoretical implementation of the ice multi-surface failure model into the explicit commercial code LS-DYNA. Step 2 deals with verification and validation of the FE implementation, this step may be called V&V analysis and its rooted in uncertainty methodologies and statistical analyses. V&V will be based on comparisons between the numerical results and the results from the ice compression tests done by Rist and Murrell (1994) which was one of the data sources for the present failure criterion. Step 3 deals with showing how the implemented model in LS-DYNA predicts actual ice pressure and indentation tests on an ice block using the MTS machine in the cold room (Wells et al., 2008) and are simulated as an example. Discussion regarding the multi-surface model, its implementation, numerical results, and model predictions are presented.Peer reviewed: NoNRC publication: Ye

Ice force modeling for DP control systems

Hydrocarbon exploration and production activities in ice-covered waters will likely require some form of dynamic positioning due to the need for quick connection/disconnection. Ice loads acting on a floating vessel in managed ice conditions can vary quickly, be large in magnitude and are difficult to predict. Existing DP control technology is based on the tried and true techniques of wind force feedforward, and stochastic state estimation of wave and current forces. Ice loads are not amenable to classical stochastic modeling techniques and the measurement of ice loads directly or indirectly (and thus the use of feedforward) is non-trivial. This paper describes work being carried out by the Institute for Ocean Technology to investiagte the nature of managed pack ice loading on a DP vessel. The approach to our future investigations will be a combination of full-scale and model scale physical tests, combined with numerical modeling.Peer reviewed: YesNRC publication: Ye

Model tests of the New Canadian Polar Icebreaker (John G. Diefenbaker)

This paper provides an overview of a model test program to evaluate performance of the new Canadian Polar icebreaker, John G. Diefenbaker design. The National Research Council Canada (NRC), the Canadian Coast Guard, STX Canada Marine (STXM) and Aker Arctic Technology (AARC) worked closely together to develop a test program, to carry out tests and to discuss test results as well as improvements. The model test program included resistance, propulsion and maneuvering (turning circle) tests both in ice and open water; ice ridge penetration tests; the wake survey, seakeeping and stationkeeping tests in open water. The model tests were carried out at the three model basins (ice tank, open water tow tank and ocean engineering basin) at the NRC\u2019s facilities in St. John\u2019s, NL. The test results were well utilized in the vessel\u2019s design development as well as providing performance evaluation tools at the conceptual design stage. Some of the test results are presented here.Peer reviewed: YesNRC publication: Ye

Numerical prediction of model podded propeller-ice interaction loads

As the interest in arctic shipping and arctic exploration of oil and gas is increasing in recent years, the number of ice class vessels is increasing rapidly. Also the choices for propulsion devices are getting wider and these include podded propulsion systems. This study is a framework for the numerical prediction of the ice interaction loads acting on a podded propeller blade. The results of this study will help us to understand the propeller-ice interaction problem more comprehensively. Several studies for propeller-ice interaction have been carried out in past few decades. Propeller-ice interaction, however, is a complicated process with a high level of uncertainties due to ice properties, ship operating conditions, and environmental conditions. Full-scale measurements involve high costs. In order to overcome these difficulties, model tests were carried out with model ice in an ice tank. The model tests provide well-controlled ice properties and interaction conditions to reduce the uncertainties. The tests were carried out in the ice tank with scaled down model ice at the National Research Council of Canada?s Institute for Ocean Technology. The ice loads acting on the propeller blade were measured with a six-component force and moment load cell fitted to one of the propeller blades. Based on the experimental results, a numerical prediction model was developed to estimate the ice loads on the propeller blade. The numerical prediction is composed of two parts: the hydrodynamic calculation, and the ice milling load calculation. The hydrodynamic calculations, i.e. propeller performance in the clear water are done by using a low order panel method. The subroutines for calculating the ice milling loads are implemented into the panel method. Several previous empirical formulae for prediction of ice loads are introduced and modified for this study. The new numerical prediction model for ice milling loads is described and compared with previous models and experimental results.Peer reviewed: YesNRC publication: Ye

Effect of ship speed on level ice edge breaking

This paper presents a numerical model of ship ice-wedge interaction to study the effect of ship speed on level ice edge breaking. The interaction process is modeled using LS-DYNA. The developed model considers ice crushing, ice flexural failure and the water foundation effect. For the ice, two different plasticity-based material models are used to represent ice crushing and ice flexural behaviors. The water foundation effect is modeled using a simple linear elastic material. The analysis is performed for a ship speed range of 0.1 to 5 ms-1 and ice thickness of 0.5 to 1.5 m. The analysis indicates that both ship speed and ice thickness significantly affect the ice breaking process. The model results are in good agreement with a number of analytical and empirical models. The model can be useful in establishing a rational basis for safe speed criteria, improving ship structural standards and tools for ice management capability assessment.Peer reviewed: YesNRC publication: Ye

Model Tests of the United States Coast Guard Heavy Polar Icebreaker Indicative Designs

This paper describes the results of model tests carried out in ice and open water conditions to evaluate performance of the United States Coast Guard (USCG) Heavy Polar Icebreaker (HPIB) indicative design. The resistance, propulsion and manoeuvring performance in ice conditions was evaluated at three different ice thicknesses (4, 6 and 8 ft.) with flexural strength 100 psi using two power setups, 36500 HP and 65000 HP. Calm water resistance and propulsion tests were also performed to evaluate open water performance. Models were constructed and tested corresponding to two indicative designs, one with triple shaft propulsion system and the other with one centre shaft and two wing podded propulsors. The present paper describes only the results for the model with triple shaft propulsion system.Peer reviewed: YesNRC publication: Ye