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為加強與國際知名專家在船舶與海洋工程水波動力學方向學術交流， 根據海底工程技術與裝備國際聯合研究中心開放課題項目工作安排，邀請新加坡海洋工程研究中心研究員梁輝（Hui Liang）來我校開展短期學術交流。Hui Liang博士将圍繞非規則波與船舶與海洋工程中相互作用的勢流理論、方法和應用開展序列學術講座。Hui Liang博士與國内多所高校合作參與了多項國家自然科學基金項目，将與參會老師交流有關方向的基金申報注意事項。

Hui Liang

Hui Liang conducted his PhD research on marine hydrodynamics at Dalian University of Technology (DUT) and Norwegian University of Science and Technology (NTNU) under a joint-cultivation programme. Since 2018, he has been a Research Scientist at Technology Centre for Offshore and Marine, Singapore (TCOMS), and acts as the deputy head of maritime system at TCOMS. Prior to his current appointment, he was a research engineer at Bureau Veritas working on the development of ship seakeeping software. Hui’s research is mainly concerned with analytical and numerical modelling of water waves and their interactions with marine structures, including: ships, offshore platforms, aquaculture structures, offshore renewable energy devices, etc. This ranges from the fundamental understanding of physical mechanism to the development of useful tools for practical applications. Hui collaborates widely with industrial and academic partners, and has authored 45 papers in peer-review journals, including: Journal of Fluid Mechanics, Physical Review Fluids, Journal of Computational Physics, Proceedings of the Royal Society A, etc. He acts as a guest editor of special issue “Recent advances in marine hydrodynamics” in Physics of Fluids.

Title 1: Liquid sloshing in an upright circular tank under periodic and transient excitations

Abstract: In this talk, the liquid sloshing problem in an upright circular tank undergoing an oscillation in a single degree of freedom is considered. A fully nonlinear time-domain harmonic polynomial cell (HPC) method based on overset mesh is developed to delve into flow physics, and the comparison is made with the weakly nonlinear multimodal theory. Both time-harmonic (or periodic) and transient-type oscillations are considered. For the time-harmonic oscillation, planar and swirling waves (including time-harmonic and periodically modulated swirling waves) occur when the excitation frequency is close to the lowest natural frequency. The swirling direction is dependent on initial conditions. The periodically modulated swirling waves switch back and forth between swirling waves and planar waves. The occurrence of swirling waves results in lateral hydrodynamic force and roll moment on top of in-line force and pitch moment components acting on the tank. A NewWave type of excitation is imposed which represents on average the most probable maximum excitation to be expected for a given sea state, and narrow-banded sloshing responses are observed. This allows application of a designer-wave type of excitation which would excite the most probable maximum response in sloshing. A focused-wave-type excitation is also considered, and an impulse-like feature is observed in the in-line force and pitch moment components. The total in-line force and pitch moment are further decomposed into inertial component, which is induced by the acceleration of the external motion, and residual component, which is closely associated with the liquid sloshing. It is found that under a focused-wave-type excitation the inertial component contribution is more dominant, while under a designer-wave-type excitation the residual component dominates instead.

Title 2:   Water wave interactions with thin-walled/plate-shaped structures

Abstract:  

Thin-walled/plate-shaped structures are omnipresent in a wide range of engineering applications. This talk is concerned with potential-flow modelling of water wave interactions with thin-walled/plate-shaped structures. A numerical model by solving hypersingular integral equations is first developed to deal with structures of small thickness, and the corresponding numerical difficulties are addressed. Besides the linear wave loads, the second-order mean drift forces/moments on thin-walled structures are derived using Stokes theorem as well as conservation of fluid momentum. In numerical examples, wave scattering by perforated flexible plates, arc-shaped breakwater, and metamaterial cylinder will be considered. Interesting physical phenomena concerning fluid resonance and non-back-scattering will be discussed.

Title3: Hydrodynamics of side-by-side offloading/bunkering

Abstract: In offshore offloading operations, two vessels are usually in a side-by-side configuration, and tanks on the vessel may experience partially filled conditions. To ensure operational safety and avoid potential hazard of collision, the understanding of wave induced motions of vessels with liquid sloshing effects is paramount. In this talk, we consider water wave interactions with side-by-side barges in a fixed-free deployment accounting for liquid sloshing in internal tanks. To investigate complex interactions among water waves, multibody system and liquid sloshing in internal tanks, a numerical model based on the boundary element method is developed, and the validity is tested by physical experiments. This study not only provides reference for numerical simulations, but also gives an insight into the motion characteristics of a floating vessel with/without liquid sloshing effects alongside a stationary vessel.

Title 4: Wave interactions with a cylinder surrounded by an arc-shaped breakwater

Abstract: Inspired by the energy island used for energy storage, conversion, and transmission, this talk explores the water wave interactions with a bottom-standing cylinder surrounded by an arc-shaped breakwater of negligible thickness. The arc-shaped breakwater can be either impermeable or porous. To analyze the problem, a semi-analytical matched eigenfunction expansion method is developed within the framework of linear potential flow theory. The accuracy of the developed semi-analytical method is verified through comparison with results obtained using the numerically-based boundary element method. Extensive discussions are conducted on various hydrodynamic responses, including wave exciting force and free surface elevations. When the breakwater is impermeable, fluid resonance occurs in the gap between the cylinder and the arc-shaped breakwater, leading to significantly large responses in both free surface elevation and hydrodynamic forces. A simple method is devised to estimate the resonant frequencies and mode shapes associated with these resonances. On the other hand, it is observed that the presence of the porous breakwater considerably reduces the free surface responses in the gap as well as the hydrodynamic loads on the cylinder. The porous breakwater effectively mitigates the occurrence of fluid resonance and offers an efficient means to dampen wave energy, providing valuable insights for wave energy dissipation and coastal engineering applications.

Title 5:  An earth-fixed observer to ship waves

Abstract:

This talk deals with the linear surface waves generated by a vessel advancing at a constant forward speed. These waves, known as ship waves, appear stationary to an observer on the vessel. Rather than exploring the well-studied stationary ship waves, this work delves into the fundamental properties of ship waves measured at earth-fixed locations. While it might have been expected that analysing these waves in an earth-fixed coordinate system would be a straightforward transformation from existing analytical theories in a moving coordinate system, the reality is quite different. The properties of waves measured at fixed locations due to a passing ship turn out to be complex and nontrivial. They exhibit unique characteristics, being notably unsteady and short-crested, despite appearing stationary to an observer on the generating vessel. The analytical expressions for the fundamental properties of these unsteady waves are made available in this work, including the amplitude, frequency, wavenumber, direction of propagation, phase velocity, and group velocity. Based on these newly derived expressions and two-point measurements, an inverse method has been presented for determining the advancing speed and the course of the motion of the moving ship responsible for the wave generation. This study sheds light on the complicated nature of ship waves as measured from fixed locations and provides valuable physical insights into their fundamental properties, leading to practical applications in determining the motion of ships based on wave measurements.

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海底工程技術與裝備國際聯合研究中心

402永利手机版网址

2023.10.13