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Theoretical approximation of Focusing-Wave Induced Load upon A Large-Scale Vertical Cylinder

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China Ocean Engineering 2017年第5期31卷 598-606页

作者： XUE Hong-xiang HU Zhe TANG Wen-yong ZHANG Xiao-ying WANG Kun-peng State Key Laboratory of Ocean Engineering Shanghai Jiao Tong University Collaborative Innovation Center for Advanced Ship and Deep-Sea Exploration Key Laboratory of Ships and Ocean Engineering of Fujian Province Jimei University School of Naval Architecture and Ocean Engineering Jiangsu University of Science and Technology

Until now, most researches into the rogue-wave-structure interaction have relied on experimental measurement and numerical simulation. Owing to the complexity of the physical mechanism of rogue waves, theoretical study on the wave-structure issue still makes little progress. In this paper, the rogue wave flow around a vertical cylinder is analytically studied within the scope of the potential theory. The rogue wave is modeled by the Gauss envelope, which is one particular case of the well-known focusing theory. The formulae of the wave-induced horizontal force and bending moment are proposed. For the convenience of engineering application, the derived formulae are simplified appropriately, and verified against numerical results. In addition, the influence of wave parameters, such as the energy focusing degree and the wave focusing position, is thoroughly investigated.

关键词： rogue wave Gauss envelope upright cylinder potential theory analytical approximation

Oscillatory velocity in boundary layer over mobile sediment bed under asymmetric wave and current conditions

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Journal of Hydrodynamics 2021年第6期33卷 1242-1254页

作者： Xin Chen Beijing Engineering Research Center of Safety and Energy Saving Technology for Water Supply Network System China Agricultural UniversityBeijing 100083China Key Laboratory of Water-Sediment Sciences and Water Disaster Prevention of Hunan Province Changsha University of Science and TechnologyChangsha 410114China

The oscillatory flow provides the major dynamic force for the mass and energy transport in estuary and coastal *** analytical approximate velocity formula is proposed to evaluate the oscillation in the boundary layer over the mobile sediment bed of the sheet flow induced by the asymmetric wave and *** velocity formula consists of an oscillatory force part and a constant force part corresponding to the Navier-Stokes equation of the asymmetric oscillatory sheet flow over the mobile sediment *** mobile sediment bed is defined by an erosion depth formula with consideration of the phase lag,the acceleration and the flow *** wave part includes the phase lead parameters from all components of the free stream *** development of the wave part is affected by the current part through the erosion depth and the boundary layer *** erosion depth,the roughness height and the boundary layer thickness of the mobile sediment bed are introduced into the current part without a transition area for the wave-current eddy *** current part is induced by the wave eddy viscosity within the boundary layer and influenced by the wave-current apparent roughness outside the boundary *** velocity profile and duration are evaluated by an approximate velocity formula through experiments for both asymmetric wave and wave-current *** oscillation feature in the boundary layer is illustrated by the approximate velocity formula through the asymmetric wave cases over the mobile sediment bed.

关键词： analytical approximation asymmetric wave and current eddy viscosity mobile sediment bed oscillatory sheet flow

Probabilistic Energy and Reserve Co-dispatch for High-renewable Power Systems and Its Convex Reformulation

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Journal of Modern Power Systems and Clean Energy 2023年第6期11卷 1734-1745页

作者： Shuwei Xu Wenchuan Wu Bin Wang Yue Yang State Key Laboratory of Power Systems Department of Electrical EngineeringTsinghua UniversityBeijing 100084China IEEE School of Electrical Engineering and Automation Hefei University of TechnologyHefei 230009China

This paper proposes a probabilistic energy and reserve co-dispatch(PERD) model to address the strong uncertainties in high-renewable power systems. The expected costs of potential renewable energy curtailment/load shedding are fully considered in this model, which avoids insufficient or excessive emergency control capacity to produce more economical reserve decisions than conventional chance-constrained dispatch methods. Furthermore, an analytical reformulation approach of PERD is proposed to make it tractable. We firstly develop an approximation technique with high precision to convert the integral terms in objective functions into analytical ones. Then, the calculation of probabilistic constraints is equivalently transformed into an unconstrained optimization problem by introducing value-at-risk(Va R) representation. Specifically, the Va R formulas can be computed by a computationally-cheap dichotomy search algorithm. Finally, the PERD model is transformed into a convex problem, which can be solved reliably and efficiently using off-the-shelf solvers. Case studies are performed on IEEE test systems and real provincial power grids in China to illustrate the scalability and efficiency of the proposed method.

关键词： Renewable energy energy and reserve dispatch emergency control stochastic optimization analytical approximation

An efficient analytical decomposition and numerical procedure for boundary layer flow on a continuous stretching surface

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Journal of University of Science and Technology Beijing 2006年第5期13卷 401-405页

作者： Xuehui Chen Liancun Zheng Xinxin Zhang Mechanical Engineering School University of Science and Technology Beijing Beijing 100083 China Applied Science School University of Science and Technology Beijing Beijing 100083 China

An efficient Adomian analytical decomposition technique for studying the momentum and heat boundary layer equations with exponentially stretching surface conditions was presented and an approximate analytical solution was obtained, which can be represented in terms of a rapid convergent power series with elegantly computable terms. The reliability and efficiency of the approximate solution were verified using numerical solutions in the literature. The approximate solution can be successfully applied to provide the values of skin friction and the temperature gradient coefficient.

关键词： momentum heat transfer stretching surface decomposition technique analytical approximation

A PERTURBATION PROCEDURE FOR LIMIT CYCLE DETERMINATION IN THREE-DIMENSIONAL NONLINEAR AUTONOMOUS DYNAMICAL SYSTEMS

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A PERTURBATION PROCEDURE FOR LIMIT CYCLE DETERMINATION IN TH...