When and where
Tuesday 8 October 2019, 11:45 Sala Consiglio, INM Headquarters Rome
Abstract
Since free-running model test (FMT) was conventionally carried out with the propeller rotational speed at propulsion point of the ship model, the scale effect on rudder effectiveness was not negligible. Moreover, engine responses as like involuntary decrease of engine rotational speed to protect them from over loading conditions was not considered. Thus, the test result couldn’t directly tell full-scale ship maneuverability. In this research, firstly, the authors proposed a method for estimating full-scale ship maneuvering motions with consideration of the engine limit for continuous operation [1], the so-called torque limit, by means of a free-running model test involving application of Rudder effectiveness and speed correction (RSC), previously proposed by the authors [2]. RSC [2] is a free-running model test method for making the maneuvering motions of a model ship using a duct-fan type auxiliary thruster [3,4] similar to those of a full-scale ship. Secondly, the authors applied the proposed method to FMT test using a tanker model in calm water and in regular waves. The test result was compared numerical simulations of maneuvering motions using the modular mathematical model. The comparison shows the validity of the proposed FMT method and clarifies that the effect of ship drifting motion on steady wave forces and moment is not negligible in order to estimate maneuvering motion in waves. Finally, FMT, using the above-mentioned method, in short-crested irregular waves and uniform wind simulated by wind loads simulator (WiLS) [5,6] was demonstrated. The authors evaluated the full-scale ship maneuvering limit in adverse weather under course-keeping condition by comparing the FMT result in the time-averaged ship speed, drift angle and rudder angle with each of the supposed threshold. The results show that the tanker becomes impossible to maneuver at head and bow waves due to the speed limit. The investigation of full-scale ship maneuvering limit is focused on only a tanker. However, this paper indicates the possibility of the direct evacuation of full-scale ship maneuverability by free-running model test in place of numerical simulations, which requires the complex formulations for various phenomena.
References
- Suzuki R., Tsukada Y. and Ueno M.; Estimation of full-scale ship manoeuvring motions from free-running model test with consideration of the operational limit of an engine, Ocean Engineering Vol.172, pp.697-711, 2018.
- Ueno, M., Suzuki, R. and Tsukada, Y.; Rudder effectiveness and speed correction in practice at tank test, Ocean Engineering, 145, pp. 124–137. 2017.
- Tsukada, Y., Ueno, M., Miyazaki, H., Takimoto, T., 2013. An auxiliary thruster for free-running model ship test. In: Proc. Of the 32nd Int. Conf. on Ocean, Offshore and Arctic Engineering. OMAE paper No. 10569.
- Tsukada, Y., Ueno, M., Tanizawa, K., Kitagawa, Y., Miyazaki, H., Suzuki, R., 2014. Development of an Auxiliary Thruster for Free-Running Model Ship Tests, vol. 20. J. of the Society of Naval Architects and Ocean Engineers, Japan, pp. 163–172 (in Japanese).
- Tsukada, Y., Suzuki, R., Ueno, M., 2017. Wind loads simulator for free-running model ship test. In: Proc. Of the 36th Int. Conf. on Ocean, Offshore and Arctic Engineering. OMAE paper No. 61158.
- Tsukada, Y., Suzuki, R., Ueno, M., 2018. Development of a Wind Loads Simulator for Free-Running Model Ship Tests in Actual Sea Condition, vols. 17–3. Papers of National Maritime Research Institute, pp. 167–186 (in Japanese).
Biography
Ryosuke Suzuki is a researcher at National Maritime Research Institute, Tokyo, Japan. His specializations are naval architecture and ship maneuverability and his recent research activities focus on a) theoretical time domain simulation of 6DOF ship maneuvering and oscillatory motions in waves and b) development of free-running model test method for the direct evaluation of full-scale ship maneuverability in waves.