10:30
Hydrodynamics in Ocean I
Chair: Yonghwan Kim
10:30
30 mins
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INSIGHT OF VORTEX STRUCTURE NEAR SUBMERGED RECTANGULAR DIKE DUE TO PROPAGATION OF SOLITARY WAVE
Chang Lin, Wei-Ying Wong, Ming-Jer Kao, Chia-Feng Hu, Hwung-Hweng Hwung, Yun-Ta Wu, Rajkumar Venkatesh Raikar, James Yang
Abstract: This paper presents the detailed flow structures above a rectangular dike and on its downstream side as well as in the breaking backwater wave due to passing of a solitary wave measured experimentally, using particle-trajectory flow visualization technique and high-speed particle image velocimetry (HSPIV). The ratio of wave height to water depth and the submergence ratio considered in the study were respectively, 0.5 and 0.71. Initially, the evolution of two vortices at the two top edges of the dike are noticed which grow in size. The vortex developed at the trailing edge is found to get entrained into the primary vortex that emanated from the leading edge and moved downstream. Due to combination of two vortices a surface wave is developed which breaks as an effect of the movement of solitary wave below the surface wave in the form of a jet flow. The breaking of the surface wave pushes the primary vortex to the bottom thereby generating another vortex near the bottom, which rises and sheds after striking the downstream face of the dike. Fur-ther, the velocity fields drawn above the rectangular dike and near the breaking backwater surface wave support the formation of series of vortices.
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11:00
30 mins
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THE RESONANT PHENOMENA OF TSUNAMI WAVE RUNUP IN THE SOUTH CHINA SEA
Xi Zhao, Hua Liu
Abstract: With the geological movements becoming active, the frequency of tsunami disaster is increasing in recent years. The giant events include the Chilean tsunami in 1960, the Indian Ocean tsunami in 2004 and Sendai, Japan tsunami in 2011. A risk map provided by the US Geological Survey (USGS), shows a potential tsunami earthquake fault zone in the South China Sea. The Manila trench is a high risk area of tsunami source. Once undersea earthquakes occur in this area, a tsunami will be triggered and the coasts of Hainan, Guangdong, Fujian, Taiwan provinces are threatened undoubtedly. Based on the actual terrain in the South China Sea, studies on the runup rules and the disaster mechanisms of tsunami waves is helpful on the development of South China Sea tsunami early warning system construction and potential tsunami disaster prevention and mitigation strategy.
The existing researches confirmed the resonant phenomena in the tsunami runup process in coastal waters with certain profiles. The aim of this work is to investigate whether runup resonance will be induced in the south coast of China if there is a tsunami in the Manila trench. In this paper, we solve the nonlinear shallow water equations to obtain the runup amplification on a profile of 4 segments. The topography on the propagation path of tsunami in the South China Sea can be simplified to a 4-segments profile. It comprises a horizontal deep seabed, a continental foundation, a continental slope and a continental shelf from the trench to the shore. We calculate the runup amplification on some piece-wise profile and analyze the resonant phenomena of certain wave frequency. As a comparison, we simulate the runup amplification by numerical model of Boussinesq equations. The runup resonance can be obtained by the numerical simulation. On the propagation path of tsunami, the resonance effects due to the piece-wise bathymetry are investigated. The runup amplification caused by the resonance for certain wave frequency is discussed.
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11:30
30 mins
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THREE-DIMENSIONAL VELOCITY MEASUREMENT ON FREE SURFACE OF AIR-CORE INTAKE VORTEX UNDER CRITICAL SUBMERGENCE
James Yang, Chang Lin, Ming-Han Kuo, Ming-Jer Kao, Chia-Feng Hu, Vadoud Naderi
Abstract: THREE-DIMENSIONAL VELOCITY MEASUREMENT ON FREE SURFACE OF AIR-CORE INTAKE VORTEX UNDER CRITICAL SUBMERGENCE
J. Yang
Hydraulic Engineering, Department of Civil and Architectural Engineering
Royal Institute of Technology (KTH), Stockholm 10044, Sweden
james.yang@vattenfall.com
C. Lin, M. H. Kuo, M. J. Kao, C. F. Hu
Division of Hydraulic Engineering, Department of Civil Engineering
National Chung Hsing University, Taichung, Taiwan
chenglin@nchu.edu.tw, hankkuo414@gmail.com,
d9362202@mail.nchu.edu.tw, g104062217@mail.nchu.edu.tw
V. Naderi
Water Science and Engineering Department, University of Tabriz,
Tabriz, Iran
vadoudnaderi@gmail.com
(*corresponding author: chenglin@nchu.edu.tw)
Abstract
A three-dimensional velocity measurement on the free surface of strong air-core vortex over a bottom intake under the condition of critical submergence was performed in the test section of a re-circulating water channel, having the dimensions of 200.0 cm long, 100.0 cm wide and 40 cm high. A vertical pipe with an inner diameter of 9.4 cm was installed at the bottom of the test section (located 125.0 cm away from the inlet) and connected to a centrifugal pump, thus forming a bottom outlet intake system. The water depth of approaching and ambient flows was kept at 11.8 cm. The mean velocity of the approaching flow was controlled at 6.7 cm/s and the counterpart of pipe flow was adjusted to be 66.5 cm/s. A strongly rotating air-core vortex with critical submergence of 11.8 cm could be thus formed. A flow visualization technique with neutrally suspending polystyrene particles was used to visualize the formation and evolution of three-dimensional flow induced by the strong air-core vortex over the entrance of the bottom intake. Three high-speed digital cameras, one being mounted upon a 2-D carriage installed beneath the roof-slab and two located at both sides of water channel, were used to capture simultaneously three sets of images with a framing rate of 200 Hz. Under such a condition, the trajectory of each traced particle on the free-surface of rotational air-core vortex could be recorded simultaneously and analyzed precisely. The aim of this study is to obtain the three velocity components of the traced particles spirally moving right on the free surface of rotational air-core vortex in either Cartesian or Cylindrical coordinates, which were never reported in the literature.
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