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Generation and Deformation of Solitary Waves

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China Ocean eng.neering 1996年第4期11卷 419-432页

作者： Chou Chung-Ren Shih Ruey-Syan Professor, dept. of harbor and river eng.neering, National Taiwan Ocean University . Graduate Student, dept. of harbor and river eng.neering, National Taiwan Ocean University dept. of harbor and river eng. National Taiwan Ocean University

Base on the Lagrangian description and finite differencing of the time step, the generation, propagation and deformation of solitary waves are simulated numerically by means of boundary element method. An algorithm to generate waves with any prescribed form is also implanted in the scheme, but in this research, solitary waves are studied. The numerical model is first verified by studying the case of a solitary wave impinging against a vertical wall. Time histories of evolution of a soliton running up on a sloping beach, as well as over a submerged obstacle are then presented. Applications to scattering problems due to solitary waves progressing over a slope onto a shelf are also shown.

关键词： Lagrangian description solitary wave boundary element method time histories

A NEW HIGH ORDER SCHEME FOR CONVECTION EQUATION AND ITS APPLICATION

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Journal of Hydrodynamics 2002年第1期14卷 81-86页

作者： Zhang Xiao-feng.(Department of river eng.neering, Wuhan University, Wuhan 430072, China) Zhang Hong-wu (Department of Hydraulic eng.neering, Tsinghua University, Beijing 100084, China) Tamotsu Takahashi, Hajime Nakagawa (Disaster Prevention Research dept. of river eng. Wuhan Univ. Wuhan 430072 China

With the undetermined coefficient method, a new high order scheme for convection equation named as HAUC was worke d out. The accuracy of the new scheme was analyzed by comparing the computed res ults with the exact solutions of 1-D pure convection equation and nonlinear con vection equation. The effectiveness of the HAUC was also examined by comparing w ith the results obtained by other schemes. Finally, it was applied to simulate 1 -D dam break flow with differenct ratios of initial upstream water dept. to do wnstream one. The results show that the scheme has the ability to simulate both undular bores and moving hydraulic jumps.

关键词： higher order scheme undetermined co efficient method dam break flow undular bore moving hydraulic jump

GRID GENERATION AND NUMERICAL SIMULATION OF 2-D river FLOW

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Journal of Hydrodynamics 2001年第2期13卷 50-54页

作者： Zhao, M.D. Li, Y.T. dept. of river eng. Wuhan Univ. Wuhan 430072 China

This paper presents new weighting functions in grid generation and new discretizing scheme of momentum equations in numerical simulation of river flow. By using the new weighting functions, the curvilinear grid could be concentrated as desired near the assigned points or lines in physical plane. By using the new discretizing scheme, the difficulties caused by movable boundary and dry riverbed can be overcome. As an application, the flow in the Wuhan Section of Yangtze river is simulated. The computational results are in good agreement with the measured results. The new method is applicable to the numerical simulation of 2-D river flow with irregular region and moveable boundary.

关键词： Computer simulation Flow of fluids Mathematical models Poisson equation Two dimensional

NUMERICAL SIMULATION OF BED DEFORMATION IN DIKE BURST

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Journal of Hydrodynamics 2001年第4期13卷 60-64页

作者： Zhang, Xiao-Feng.Yu, Ming-Hui dept. of river eng. Wuhan Univ. Wuhan 430072 China

The key point in the numerical simulation of breach growth and bed deformation process in dike burst is the accurate computation of flow and sediment transport. A numerical model for horizontal 2-D non-uniform sediment was developed to simulate the bed deformation process in the dike burst. The first-order scheme was used in computation. Several simulated results were worked out to demonstrate the applicability of the numerical model.

关键词： Computer simulation Levees Mathematical models Scour

NUMERICAL SIMULATION OF SEPARATED FLOW NEAR GROYNE

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Journal of Hydrodynamics 2002年第4期14卷 47-52页

作者： Jiang, Chang-Bo Chen, Yong-Kuan Bai, Yu-Chuan Zhao, Zi-Dan dept. of river and Coast eng. Changsha Commun. Univ. Changsha 410076 China dept. of Hydraulic eng. Tsinghua Univ. Beijing 100084 China Inst. of sediment on river eng. Tianjian Univ. Tianjian 300072 China

A numerical model was developed to simulate the flow around non-submeged groyne in two dimensions, which was based on N-S equations with Smagorinsky's subgrid-scale turbulence model. Flow phenomenon and results measured practically agree with the calculation results very well, and this model could be used to simulate the characteristics of the eddies of upper and down reaches around spur-dikes successfully.

关键词： Computational fluid dynamics Computer simulation Erosion Mathematical models Navier Stokes equations Turbulent flow

Hydrodynamic Performance of Vertical Porous Structures Under Regular Waves

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China Ocean eng.neering 2013年第4期27卷 451-468页

作者： A.S.Koraim O.S.Rageh Water and Water Structure eng. dept. Faculty of Eng. Zagazig University Irrigation and Hydraulics dept. Faculty of Eng. El-Mansoura University

The hydrodynamic efficiency of the vertical porous structures is investigated under regular waves by use of physical models. The hydrodynamic efficiency of the breakwater is presented in terms of the wave transmission （kt）, reflection （kr） and energy dissipation （ka） coefficients. Different wave and structural parameters affecting the breakwater efficiency are tested. It is found that, the transmission coefficient （kt） decreases with the increase of the relative water dept. （h/L）, the wave steepness （Hi^L）, the relative breakwater widths （B/L, B/h）, the relative breakwater height （D/h）, and the breakwater porosity （n）. The reflection coefficient （kr） takes the opposite trend of kt when D/h=l.25 and it decreases with the increasing h/L, HJL and B/L when D/h〈1.0. The dissipation coefficient （kd） increases with the increasing h/L, HilL and B/L when D/h〈_l.O and it decreases when D/h=l.25. In which, it is possible to achieve values ofkt smaller than 0.3, k~ larger than 0.5, and kd larger than 0.6 when D/h=1.25, B/h=0.6, h/L〉0.22, B/L〉O. 13, and H/L 〉0.04. Empirical equations are developed for the estimation of the transmission and reflection coefficients. The results of these equations are compared with other experimental and theoretical results and a reasonable agreement is obtained.

关键词： water waves porous breakwaters wave attenuation wave transmission wave reflection wave dissipation

EFFECT OF THE OPEN CRACK ON THE PULL-IN INSTABILITY OF AN ELECTROSTATICALLY ACTUATED MICRO-BEAM

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Acta Mechanica Solida Sinica 2012年第6期25卷 627-637页

作者： Asadollah Motallebi Mohammad Fathalilou Ghader Rezazadeh Mech. eng. dept. Islamic Azad University Mech. eng. dept. Urmia University

In this paper, the effects of the open crack on the static and dynamic pull-in volt- ages of an electrostatically actuated fixed-fixed and cantilever micro-beam are investigated. By presenting a mathematical modeling, the governing static and dynamic equations are solved by SSLM and Galerkin-based Reduced Order Model, respectively. Then, each single-side open crack in the micro-beam is modeled by a massless rotational spring and the cracked mode shapes and corresponding natural frequencies are calculated by considering the boundary and patching con- ditions and using transfer matrix methods. Finally, the effects of the crack dept. ratio, crack position and crack number on the pull-in voltage of the micro-beams are studied. It is shown that beside the residual stresses created in the machining process, the crack（s） can be initiated, growth and consequently change the pull-in voltage of the system by decreasing the natural frequencies. The results show that the crack position is effective beside the crack dept. ratio in decreasing the pull-in voltage. Also it is shown that in the fixed-fixed micro-beam there are several points for the crack location in which, the pull-in voltage is extremum.

关键词： MEMS open crack electrostatic pull-in instability

Computational Fluid Dynamic Simulation of Liquid-Liquid Mixing in a Static Double-T-shaped Micromixer

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过程工程学报 2008年第6期8卷 1080-1084页

作者： Elmabruk A. MANSUR 王运东戴猷元 The State Key Lab. Chem. eng. Dept. Chem. Eng.Tsinghua University

The laminar flow structure and mixing performance of T-shaped and double-T-shaped micromixers with rectangular cross-section have been investigated using computational fluid dynamic (CFD) simulation. FLUENT software is used to evaluate the mixing efficiency. The numerical simulation results show that the presented double-T-micromixer is highly efficient over T-shaped micromixer. The performance of double-T-micromixer with and without static mixing elements (SME) is also investigated. The enhancement in mixing performance is thought to be caused by the generation of eddies and lateral velocity component when the mixture flows through these elements. Mixing efficiency as higher as 97% is reached within a mixing leng.h of 320 μm downstream from the first T-junction with the enhancement of three SMEs.

关键词：计算方法流体动力学模拟方法液液混合双T形微混合器物理过程

Experimental Study on the Effects of A Breakwater on Wave Field Characteristics

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China Ocean eng.neering 2000年第2期15卷 229-242页

作者：尹彰周宗仁黄伟柏 Ocean eng.neering Laboratory Dept. of Harbour and River Eng. National Taiwan Ocean University 20224 Keelung Taiwan

Studies on the possible effects of a detached breakwater on the characteristics of the wave field are carried out experimentally. A serpentine wave generator is used to generate both uni- and multi- directional waves. Characteristics of the wave fields analyzed here include the wave field directionality, and the probability distributions of surface elevations and of the wave heights. Owing to the presence of the breakwater. waves outside the harbour are Found to be reflected with, however, concentrated energy within the harbour entrance. In general. wave heights can be approximated with a Rayleigh distribution, with occasional deviations from the theory. This occurs more frequently for waves with higher peak frequency values than for those with lower values both for uni- and multi-directional waves. Surface elevations can be approximated with the Gaussian model, although the Edgeworth's form of the type A Gram- Charlier series expansions would yield better fits. Wave directionality is found to have no discernible effects on the statistical characteristics of the wave field.

关键词： wave directionality statistical distributions surface elevations wave heights