Abstract
The interactions between the main hull and demi-hull of trimarans have been arousing increasing attention, and detailed circumferential flow fields greatly influence trimaran research. In this research, the unsteady wake flow field of a trimaran was obtained by Reynolds-Averaged Navier-Stokes (RANS) equations on the basis of the viscous flow principles with consideration of the heaving and pitching of the trimaran. Then, we designed an experimental method based on particle-image velocimetry (PIV) and obtained a detailed flow field between the main hull and demi-hull of the trimaran. A trimaran model with one demi-hull made of polycarbonate material with 90% light transmission rate and a refractive index 1.58 (close to that of water 1.33) was manufactured as the experiment sample. Using polycarbonate material, the laser-sheet light-source transmission and high-speed camera recording problems were effectively rectified. Moreover, a nonstandard calibration was added into the PIV flow field measurement system. Then, we established an inverse three-dimensional (3D) distortion coordinate system and obtained the corresponding coordinates by using optics calculations. Further, the PIV system spatial mapping was corrected, and the real flow field was obtained. The simulation results were highly consistent with the experimental data, which showed the methods established in this study provided a strong reference for obtaining the detailed flow field information between the main hull and demi-hull of trimarans.
Highlights
As researchers seek to discover the fundamental properties associated with object motion, the focus of research on basic fluid mechanics problems in shipbuilding and ocean engineering has shifted from determining macroscopic forces and moments to measuring detailed flow fields
Larsson et al [10] collected, analyzed, and compiled 18 test cases pertaining to the KRISO container ship (KCS), KVLCC, and DTMB5414 ships, which were presented by 33 research groups at the Gothenburg 2010 Workshop on Numerical Hydrodynamics
After performing iterations for a specific period of time, the forces acting on the hull gradually reach a balance, and the circumferential flow field around the hull reaches a dynamic equilibrium under the current ship speed
Summary
As researchers seek to discover the fundamental properties associated with object motion, the focus of research on basic fluid mechanics problems in shipbuilding and ocean engineering has shifted from determining macroscopic forces and moments to measuring detailed flow fields. Choi et al [5] conducted numerical analyses on the resistance, propulsion, and surrounding flow of multiple wide ships based on CFD results He et al [6] studied the disturbance effects of a high-speed catamaran on its resistance, heaving, and pitching. Larsson et al [10] collected, analyzed, and compiled 18 test cases pertaining to the KCS, KVLCC, and DTMB5414 ships, which were presented by 33 research groups at the Gothenburg 2010 Workshop on Numerical Hydrodynamics These previous studies fully demonstrated the reliability of CFD tools in researching a ship’s hydrodynamic performance, and provide references for obtaining detailed flow fields between the main body and the demi-body of the trimaran considered in this work. Eng. 2020, 8, 975 numerical and experimental methods employed in this study can serve as important reference material for further research into the flow fields of catamaran and trimaran ships
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