Abstract
Abstract In order to obtain the hydrodynamic coefficients that can save cost and meet the accuracy requirements, a new hydrodynamic test platform based on a 6DoF (six degrees of freedom) parallel mechanism is proposed in this paper. The test platform can drive the ship to move in six degrees of freedom. By using this experimental platform, the corresponding hydrodynamic coefficients can be measured. Firstly, the structure of the new device is introduced. The working principle of the model is deduced based on the mathematical model. Then the hydrodynamic coefficients of a test ship model of a KELC tank ship with a scale of 1:150 are measured and 8 typical hydrodynamic coefficients are obtained. Finally, the measured data are compared with the value of a real ship. The deviation is less than 10% which meets the technical requirements of the practical project. The efficiency of measuring the hydrodynamic coefficients of physical models of ships and offshore structures is improved by the device. The method of measuring the hydrodynamic coefficients by using the proposed platform provides a certain reference for predicting the hydrodynamic performance of ships and offshore structures.
Highlights
The hydrodynamic coefficients are the coefficients of the equations of motion of a ship or submersible
The main method used is captive ship model testing, which mainly includes the oblique running test (ORT) [6], which is known as the straight-line towing test, rotating arm test (RAT) [7], and plane motion mechanism (PMM) test [8,9]
In order to measure the hydrodynamic coefficients of the test ship model, captive model tests were carried out on the test ship model by using the 6DoF parallel mechanism test device
Summary
The hydrodynamic coefficients are the coefficients of the equations of motion of a ship or submersible. There are three main methods to obtain the hydrodynamic coefficients: the captive or free self-propelled model test, computer numerical simulation, and semi-theoretical and semi-empirical estimation [3,4,5]. POLISH MARITIME RESEARCH, No 3/2020 a 1:1 ship model to conduct a straight-line towing test in the towing pool and obtained the hydrodynamic coefficients of the submersible at different speeds and depths They further studied the influence of the free surface on the resistance and lift coefficient. In order to research the hydrodynamic performance of small submersibles in the preliminary design, Gala et al [11] obtained the hydrodynamic coefficients of small submersibles at different drift angles and attack angles using the ORT test and numerical simulation methods. We define two right hand Cartesian coordinates which are shown in Fig. 2. {B} is the coordinate point vector of the upper control platform and its corresponding coordinate system O-XBYBZB is a fixed coordinate system. {b} is the coordinate point vector of the bearing hinge point in the lower control platform and its corresponding coordinate system O-XbYbZb is a moving coordinate system
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