When and where
Tuesday 8 October 2019, 12:25 Sala Consiglio, INM Headquarters Rome
Abstract
The authors have developed a duct fan type auxiliary thruster that consists of a duct fan, a signal amplifier, a load cell, and a PC [1, 2]. The auxiliary thruster can provide a free-running ship model with additional longitudinal force controlled by the PC. The mechanism makes it possible relatively easily to adjust the propeller load of a free-running ship model to designated time varying values. Since the large difference of Reynolds numbers between model and full-scale ships has long compelled us to accept the large difference of propeller lad between them, the development should lead to innovative free-running model test methodologies. This report proposes, after brief introduction of the development of the auxiliary thruster, a couple of new free-running model test procedures making use of the auxiliary thruster assembled for practical use. One is the rudder effectiveness correction that realizes full-scale equivalent maneuvering motion using free-running model ships [3]. The other is a free-running test to measure the speed decrease in waves using a model ship running at a propeller rate of revolution corresponding full-scale ship self-propulsion point. These examples offer promising prospects of the duct fan type thruster. Secondly, the authors have developed a wind loads simulator that enables us to carry out free-running model tests with consideration of wind effects. The wind loads simulator provides a free-running model ship with simulated wind loads taking account of supposed true wind speed and direction, and instantaneous ship model speed, drift angle, and heading angle. It does not generate environmental wind but exerts forces and moment on a ship model using three pairs of duct fans whose system is similar to the auxiliary thruster. A control PC calculates time varying longitudinal and lateral wind forces and yaw moment using wind loads coefficients estimated beforehand and ship motion data measured in model test, and distribute them to three pairs of duct fans. As the auxiliary thruster feed-back control ensures the intended wind loads using data from load cells on which the duct fans are mounted and those from accelerometers for correcting inertia forces of the duct fans. This paper reports the concept, configuration, and control procedure of the wind loads simulator, and presents test data to validate it. The tests include preliminary tests on shore and a free-running model tests in a model basin. The free-running model tests are turning, zigzag and course keeping tests in wind, and in wind and regular wave; and course keeping tests in wind and short-crested irregular waves, The test data confirm the effectiveness and usefulness of the wind loads simulator as a device in free-running model tests to evaluate ship maneuvering performance in actual sea conditions.
References
- 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).
- 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., 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
Yoshiaki Tsukada is a senior researcher at National Maritime Research Institute, Tokyo, Japan. His specializations are model testing, resistance and propulsion, and maneuverability. His recent research focuses on the a) development and control of an auxiliary thruster for ship model testing in calm water and in waves and b) development and control of a wind loads simulator for free-running model test in wind .