Abstract
There has been increasing interest in the loads caused during interaction between ship propellers and ice. Recent research into propeller ice interaction has produced inverse models that can be used to estimate the propeller moment induced by ice impacts. These models rely on the measurement of the output response of the propulsion shaft, which is inverted to obtain the input propeller load. The particular model considered here makes use of modal superposition to invert the measured shaft response. Though the model has been validated numerically and used with full-scale response data, it has not been validated using simultaneous input and output measurements. Reliable full-scale simultaneous measurements can be difficult to obtain due to the harsh conditions experienced during propeller-ice interactions, and the cost involved with direct measurement of propeller loads. Thus, the use of a laboratory rig to verify the inverse method is investigated. An inverse model based on the use of modal superposition to represent the propulsion shaft as a continuous system has been implemented alongside a laboratory scale rig. The input loads and output responses are measured simultaneously during experiments with the scale model. These output responses are provided to the inverse model, and its estimation of the input load are compared to the measured loads. The comparison provides information about the accuracy of the estimations provided by the inverse model. A limitation in the inverse model, that spurious transients at the shaft natural frquency appear in the estimations, has been found and discussed.
