A study of methods to predict added resistance in waves
Student: Martin Alexandersson
Supervisior: Mikael Palmquist
Examiner: Karl Garme
This thesis is an overview of added resistance in waves, available methods and how a simplified method can be developed.
Added resistance in waves is indeed a very complicated problem. The present methods, most of them developed during the 1970s, give reasonable results for head waves. But for quartering and following waves, the methods have low accuracy, due to uncertainties in strip calculated ship motions for these cases, and the ability to account for roll and yaw motions.
In this thesis Gerristma and Beukelman’s method and Boese’s method to calculate added resistance is implemented and validated against published calculation results, from previous implementations. The implementations are also evaluated against published experimental results in head waves. These evaluations show that added resistance with good accuracy can be calculated for head waves using Gerritsma and Beukelman’s method.
This thesis also shows how a simplified method to calculate added resistance in waves can be developed. This simplified method only uses the ships main particulars to describe the hull. The method is intended to be used when the entire hull geometry is not available, for instance in the pre-study of a new ship design. The idea with this method is to estimate transfer functions for added resistance without using strip calculations. The transfer functions are parameterized with three parameters, peak value, peak frequency and spreading. Expressions for these parameters are derived with regression analysis, based on analytical results from Gerritsma and Beukelman’s method. The simplified method has an accuracy of about 25%, which is about the same amount that usually can be expected of a method to