14th International Conference on Hydrodynamics

Wuxi, China 21-25 October, 2022

There will be four invited keynote speakers to present their lectures on ICHD2022. The speakers and titles of the keynotes are summarized as follows:

Speaker 1: Prof. Philip L-F Liu.pdf
Keynote: Tonga Volcano Explosion Generated Tsunamis in The Pacific Ocean and Beyond
Philip L.-F. LIU, Pablo HIGUERA, and Zhiyuan REN
Department of Civil and Environmental Engineering
National University of Singapore
Abstract
The Hunga Tonga – Hunga Ha’apai submarine volcano exploded at 4:10AM UTC on 15th January 2022 on the Tongan archipelago. The eruption was so violent that created a plume of approximately 500 km in diameter and propelled ash 55 km up into the mesosphere and produced a pressure shock wave, inducing atmospheric pressure disturbances that have been captured for several days by weather stations around the Globe. The front of this air pressure wave travelled at approximately 0.9 Mach (1,127 km/h) and circled the Earth several times, decaying progressively. Shortly after the explosion, tsunami waves were detected in and along the coasts of the Pacific Ocean. The initial arrival time was earlier than expected based on the propagation speed of long gravity waves and coincides with the arrival time of the air pressure wave. Furthermore, tsunami waves were also detected in water bodies, too far away from the source for the tsunami waves to reach directly. Similar fluctuations in the form of tsunami or long waves captured by tidal gauges in an extremely far field had already been reported in previous volcanic explosion events, as for example those recorded in France and UK for the Krakatoa eruption in 1883. In this talk we will first illustrate how the moving air pressure front generates tsunamis and demonstrate the tsunami characteristics at far field, using idealized problem. We will then use the existing data from a global numerical simulation of the air pressure wave to force the shallow water wave model and study the sea level responses in the Pacific Ocean and beyond. Numerical results are compared with the DART buoy data, which require corrections because of the presence of air pressure. The numerical model predicts well the arrival time and the magnitudes of the leading forced waves. Moreover, the numerical can demonstrate the appearance of trailing free wave trains behind the leading forced waves. 



Speaker 2: Prof. Yonghwan Kim.pdf
Keynote: Comparative Study on Added Resistance in Waves
Yonghwan Kim
Seoul National University
Seoul, Korea
Abstract
Recent activities for decarbonization in marine engineering includes the design of hull form to minimize the ship fuel in actual seaways, and IMO started an international regulation for the EEDI(energy efficiency design index). In the EEDI, the speed loss effect due to added resistance in actual seaways, so-called weather factor, is included. Prediction of added resistance is an essential element in the prediction of ship speed in waves. The degree of speed loss in seaways is strongly dependent on the added resistance due to wave and wind, and the correction of ship speed from the data measured at sea trial is affected by how much added resistance is.
There have been many researches on ship added resistance in waves. Most of them were focused on head sea conditions, based on the potential theory and linear seakeeping analysis. Maruo’s formula was popular and some asymptotic or empirical formulas have been applied for short wave ranges. Nowadays, heavier computation is possible, and panel method and CFD programs are getting more popular.
In this presentation, recent research activities of our group will be introduced. For about fourteen years, our group has developed computational methods, database, and theoretical formulas which are related to added resistance. Recently SNU carried out a government-funded research project collaborating with shipbuilding industries and ship classification societies. Furthermore, some research outcomes were submitted to IMO for the sea trial procedure. In this presentation, some of such outcomes will be introduced, particularly focusing on the following topics:
- Benchmark test of added resistance computation for different ship types
- Comparison between different computational methods and formulae
- Added resistance in oblique waves: Experiment vs. Computation
- Enhanced asymptotic formula for added resistance in short waves
The presentation will be based on our technical paper of JH Lee et al. (Ocean Engineering, 2021), DM Park et al. (Ocean Engineering, 2019), KK. Yang et al. (Ocean Engineering, PACOMS, 2017) and etc. New findings and new formulae for added resistance and ship speed loss in waves will be explained, some key results will be shown.



Speaker 3: Prof. Claudio Lugni.pdf
Keynote: An holistic vision of the Marine Renewable Energy: the experience of the Floating Energy Archipelago in the Mediterranean Sea
C.Lugni, A. Bardazzi, A.Lucarelli, C.Pilloton
CNR-INM
Abstract
The production of energy from renewable sources is one of the main tools to lead Europe towards a completely environmentally sustainable energy production. Through the great plan of the Green Deal for sustainable relaunch, the European Union aims to transform Europe into a prosperous and fair society, through the development of a circular, modern and competitive economy, which can allow the achievement of climate neutrality by 2050, and identifies in marine renewable technologies (e.g sun, wind, waves, currents) and in their use for the production of clean fuel the keystone for the transition of the European-energy system towards clean energy (Clean Energy Transition).
A novel strategy for the harvesting of the marine renewable energy has been first theorized since 2015 by the CNR-INM research team coordinated by Dr. Lugni: the Floating Energy Archipelago (FEA). Conceived for deep-water marine areas, typical of the Mediterranean sea, the FEA is a prototype of floating and modular smart-city, energetically independent, being able to harvest the marine renewable energy (sun, wind, geothermal, wave) and use it for the in situ human and industrial activity.
This interdisciplinary concept collects most of the research findings and experiences of the CNR-INM research team, ranging from the design of novel structures for marine renewable energies, i.e. at low cost and with low environmental footprint, to the use of novel underwater bio-inspired marine vehicles for structural and environmental monitoring.
The Energy Archipelago idea aims to overcome the technological obstacles connected to the construction in the open sea of power generation plants from marine renewable sources (wind, waves) integrated with photovoltaic systems, and to build demonstration prototypes of energy islands of increasing power, whose modularity will allow the construction of archipelagos i) of suitable power for different geographical locations, ii) with combination of energy harvesting systems and technologies properly optimised for the energy resource available in the site and iii) with possible in situ use of the energy stored.
The lecture focuses on the main hydrodynamic challenges and perspectives connected with the design and the implementation of the FEA. Emphasis will be given to the presentation of the results of the Research Project “Energy at Sea”, recently funded by the Italian Ministry of the Ecological Transition. Within the same project, in 2021 CNR-INM designed and installed at sea, close to the Naples port, the first prototype existing in the Med Sea of a Floating Offshore Wind turbine (in cooperation with Saipem) and proposed a new concept of flexible floating offshore solar island, characterised by a low cost, paving the way to the first prototype of the new concept of floating smart-city. For the first time, the hydrodynamic monitoring data of a quite extensive experimental activity at real sea and the comparison with the numerical data of suitable solvers developed and of model experiments performed at CNR-INM basin, will be presented and discussed.



Speaker 4: Dr. Shuxia Bu.pdf
Keynote: Experimental and Numerical investigation on damage stability in waves
Shuxia Bu, Min Gu
China Ship Scientific Research Center, Wuxi, China
Abstract 
The catastrophic accidents of maritime ships are mostly related to the insufficient ship stability in waves, and the flooding of water into damaged compartments due to various reasons increases the uncertainty of instability, which has attracted great attention. The assessment method of damaged ship stability is very complicated due to the highly non-linear behavior. Therefore, it’s of great theoretical and practical significance to investigate the problem of ship stability coupled with flooding water.
This presentation focuses on the investigation of the damaged ship motions through experimental tests and numerical simulations. Our team has developed numerical simulation methods for damaged ship stability, and also carried out detailed experimental model tests. In this presentation, ourworks related to damaged ship stability will be introduced, particularly focusing on some recent research:
(1) Time-domain assessment method for the damaged ship motion coupled with water inside the compartment.
(2) Model tests on damaged ship motion in waves with newly designed measuring equipment.
(3) New findings from the comparison of numerical simulation and model tests.
(4) Nonlinear behavior of damaged ships in regular and irregular waves.