A Numerical Ice Load Prediction Model Based on Ice-Hull Collision Mechanism

Round 1

Reviewer 1 Report

The authors present a sufficiently novel approach to calculating the forces acting on a ship hull in level unbroken ice. This reviewer has a few comments intended to improve the quality of the paper;

It appears that there is no randomness included in the model. If this is the case, then it should be clearly stated, along with suggestions for introducing randomness in the future.  The authors should explain why they only considered a single ice collision at the shoulder in the low speed case. Was this on the basis of observations from the model experiments? Was this feature not seen at other speed, and if not why? Were the results sensitive to the number of elements used to discretize the waterlines?  The comparison of the results is done in a curious way (figures 14, 15, 16). The convention from model experiments is to present mean force value, which is calculated as the first moment of the measure data. The reduced value for the predicted data is based on the second moment of the data (standard deviation or RMS). Standard deviation is second moment of the data, RMS is equivalent to second moment for a zero mean. The reviewer understands why the authors want to include the spread of the data as well as a steady value, but why not compare both model experiments and simulations on the basis of first and second moments (e.g. mean and standard deviation)?  How do the comments on 'safe speed' compare to actual operator guidelines for speed in ice, such as the Russian Register. The change in speed for a 0.1m change in ice thickness seems to be very high.  The crushing and flexural strength used in the simulation of the IWW barge are not given. 

Author Response

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Reviewer 2 Report

This paper treats ice load predictions on a ships hull. Authors use empirical models developed in various literature to compose their numerical model. The proposed numerical model combines the effect of ice crushing and ice bending empirical models to calculate the ice-hull impact force.  

The topic is interesting for a publication and method looks sound. The numerical model tries to calculate the impact force by matching two phenomena of ice-hull interaction, the crushing and bending. Compared to experimental data, the model fails to predict the maximal impact force for low Froude numbers due to matching condition used in the numerical model. A proposed numerical model based on empirical approach is fast and accurate enough to support the design stage of IWW ice ship. More accurate numerical models, like FEM based, are more accurate but far more computationally expensive. Maybe the use of complex FEM model is a good replacement to experiments in the stage of new parameters searches to improve the matching condition in the existing numerical model.

It would be worth to continue with the investigation for a new condition of ice crunching and ice bending matching that would predict maximal impact force on a wider Froude number span.  Another very interesting investigation is to start with parameter sensitivity analysis to identify the relevant parameters in the existing numerical model.

Author Response

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