Estimating added power in waves for ships through analysis of operational data

The accuracy of added power estimation using full scale operational data is directly related to the accuracy of determining the calm water power. Firstly, this paper focuses on a detailed analysis of the calm water powering, using voyage (operation) data supported by and compared to standard estimation techniques and model test data. Further, a method to quantify the added power in weather is developed. The added power due to the influence of waves and wind is treated as the difference between measured shaft power and calm water power requirement. It is shown that both quality and quantity of data is important to model calm water power accurately. The operational data suggests that trim by stern is favorable at lower speeds and has little effect with increase in speed. The added power in waves for most operational speeds considered is less than 10%