检索结果-南通市图书馆

Nonlinear dynamical characteristics of bed load motion

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2006年第3期49卷 365-384页

作者： chiu-On ng Department of Mechanical Engineering the University of Hong Kong Hong Kong China

Bed forms of various kinds that evolve naturally on the bottom of sandy coasts and rivers are a result of the kinematics of bed load transport. Based on the group motion of particles in the bed load within the bottom layer, a study on the nonlinear dy- namics of bed load transport is presented in this paper. It is found that some development stages, such as the initiation, the equilibrium sediment transport, and the transition from a smooth bed to sand dunes, can be accounted for by different states in the nonlinear sys- tem of the bed load transport. It is verified by comparison with experimental data reported by Laboratoire Nationae D’Hydraulique, Chatou, France, that the evolution from a smooth bed to sand dunes is determined by mutation in the bed load transport. This paper pre- sents results that may offer theoretical explanations to the experimental observations. It is also an attempt to apply the state-of-the-art nonlinear science to the classical sediment transport mechanics.

关键词： bed load, bed form, nonlinear dynamics.

On the time development of dispersion in electroosmotic flow througha rectangular channel

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2012年第3期28卷 631-643页

作者： Suvadip Paul chiu-On ng Department of Mechanical Engineering The University of Hong Kong

This is an analytical study on the time develop- ment of hydrodynamic dispersion of an inert species in elec- troosmotic flow through a rectangular channel. The objec- tive is to determine how the channel side walls may affect the dispersion coefficient at different instants of time. To this end, the generalized dispersion model, which is valid for short and long times, is employed in the present study. An- alytical expressions are derived for the convection and dis- persion coefficients as functions of time, the aspect ratio of the channel, and the Debye-Htickel parameter representing the thickness of the electric double layer. For transport in a channel of large aspect ratio, the dispersion may undergo several stages of transience. The initial, fast time develop- ment is controlled by molecular diffusion across the narrow channel height, while the later, slower time development is governed by diffusion across the wider channel breadth. For a sufficiently large aspect ratio, there can be an interlude between these two periods during which the coefficient is nearly steady, signifying the resemblance of the transport to that in a parallel-plate channel. Given a sufficiently long time, the dispersion coefficient will reach a fully-developed steady value that may be several times higher than that with- out the side wall effects. The time scales for these periods of transience are identified in this paper.

关键词： Taylor dispersion. Electroosmotic flow. Gener-alized dispersion model

Rotating electroosmotic flow of an Eyring fluid

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2017年第2期33卷 295-315页

作者： Cheng Qi chiu-On ng Department of Mechanical Engineering The University of Hong Kong Hong Kong China

A perturbation analysis is presented in this paper for the electroosmotic (EO) flow of an Eyring fluid through a wide rectangular microchannel that rotates about an axis perpendicular to its own. Mildly shear-thinning rheology is assumed such that at the leading order the problem reduces to that of Newtonian EO flow in a rotating channel, while the shear thinning effect shows up in a higher-order problem. Using the relaxation time as the small ordering parameter, analytical solutions are deduced for the leading- as well as first-order problems in terms of the dimensionless Debye and rotation parameters. The velocity profiles of the Ekman-electric double layer (EDL) layer, which is the boundary layer that arises when the Ekman layer and the EDL are comparably thin, are also deduced for an Eyring fluid. It is shown that the present perturbation model can yield results that are close to the exact solutions even when the ordering parameter is as large as order unity. By this order of the relaxation time parameter, the enhancing effect on the rotating EO flow due to shear-thinning Eyring rheology can be significant.

关键词： Electroosmotic flow Eyring fluid Rotating channel

WAVE INDUCED OSCILLATORY AND STEADY FLOWS IN THE ANNULUS OF A CATHETERIZED VISCOELASTIC TUBE

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2010年第5期22卷 605-617页

作者： ng chiu-on CHAng Yin-Yee Department of Mechanical Engineering The University of Hong Kong

A perturbation analysis based on equations of motion in Lagrangian form is presented for the oscillatory and time-mean viscous flows induced by a propagating wave of small amplitude in an annulus with a viscoelastic outer wall. Owing to the steady streaming effect, the existence of a catheter in a blood vessel brings in an additional steady pressure gradient, a correction to that predicted by the linear theory, and an additional steady shear stress, which may increase the possibility of hemolysis of red blood cells.

关键词： annulus flow steady streaming catheterized artery

The effect of variable viscosity on the flow and heat transfer of a viscous Agwater and Cu-water nanofluids

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2013年第1期25卷 1-9页

作者： VAJRAVELU Kuppalapalle PRASAD Kerehalli Vinayaka ng chiu-on Department of Mathematics University of Central Florida Department of Mathematics VSK University Department of Mechanical Engineering The University of Hong Kong

A numerical study is carried out to study the effects of the temperature dependent viscosity on the flow and heat transfer of a nanofluid over a flat surface in the presence of viscous dissipation. The governing nonlinear partial differential equations are transformed into nonlinear ordinary differential equations, and are solved numerically by the Keller-box method. The numerical results indicate that the effect of nanoparticle volume fraction is to increase the heat transfer and hence enhance the thermal boundary layer thickness. This is true even in the presence of variable viscosity and the viscous dissipation. Furthermore, the results obtained for heat transfer characteristics with nanoparticles reveal many interesting behaviors that warrant further study on the effects of the ＂nano-solid-particles＂.

关键词： nanofluid particles variable viscosity boundary layers viscous dissipation Keller-box method

ELECTROHYDRODYNAMIC DISPERSION OF DEFORMABLE AEROSOLS IN THE PRESENCE OF AN ELECTRIC FIELD AND CHEMICAL REACTION USIng TAYLOR DISPERSION MODEL

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2011年第2期23卷 247-257页

作者： RUDRAIAH N. DEVARAJU N. ng chiu-on UGC-CAS in Fluid Mechanics Department of Mathematics Bangalore University Bangalore-560 001 India National Research Institute for Applied Mathematics (NRIAM) Bangalore-560 070 India Department of Mechanical Engineering The University of Hong Kong

Under the effects of electric field and chemical reaction, the problem of dispersion of aerosols in a poorly conducting fluid in a channel is solved analytically using the mixture theory together with a regular perturbation technique. It is shown that the aerosols are dispersed relative to a plane moving with the mean speed of atmospheric fluid as well as the mean speed of agglomeration of aerosol with a relative diffusion coefficient, called the Taylor dispersion coefficient. This coefficient is numerically computed and the results reveal that it increases with an increase in the electric number, but decreases with increasing porous parameter. The physical explanations for the phenomena are given in this article.

关键词： dispersion aerosols electrohydrodynamics mixture theory

Experimental investigation of the effect of flow turbulence and sediment transport patterns on the adsorption of cadmium ions onto sediment particles

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2007年第6期19卷 696-703页

作者： HUAng Sui-liang ng chiu-on GUO Qi-zhong Numerical Simulation Group for Water Environment College of Environmental Science and Engineering Nankai University Tianjin 300071 China Deptartment of Mechanical Engineering The University of Hong Kong Pokfulam Road Hong Kong Department of Civil and Environmental Engineering Rutgers State University of New Jersey 623 Bowser Road Piscataway NJ 08854 USA

The mechanism of flow turbulence, sediment supply conditions, and sediment transport patterns that affect the adsorption of cadmium ions onto sediment particles in natural waters are experimentally simulated and studied both in batch reactors and in a turbulence simulation tank. By changing the agitation conditions, the sediment transport in batch reactors can be categorized into bottom sediment-dominated sediment and suspended sediment-dominated sediment. It is found that the adsorption rate of bottom sediment is much less than that of suspended sediment, but the sediment transport pattern does not affect the final （equilibrium） concentration of dissolved cadmium. This result indicates that the parameters of an adsorption isotherm are the same regardless of the sediment transport pattern. In the turbulence simulation tank, the turbulence is generated by harmonic grid-stirred motions, and the turbulence intensity is quantified in terms of eddy diffusivity, which is equal to 9.84F （F is the harmonic vibration frequency） and is comparable to natural surface water conditions. When the turbulence intensity of flow is low and sediment particles stay as bottom sediment, the adsorption rate is significantly low, and the adsorption quantity compared with that of suspended sediment is negligible in the 6 h duration of the experiment. This result greatly favors the simplification of the numerical modeling of heavy metal pollutant transformation in natural rivers. When the turbulence intensity is high but bottom sediment persists, the rate and extent of descent of the dissolved cadmium concentration in the tank noticeably increase, and the time that is required to reach adsorption equilibrium also increases considerably due to the continuous exchange that occurs between the suspended sediment and the bottom sediment. A comparison of the results of the experiments in the batch reactor and those in the turbulence simulation tank reveals that the adsorption ability of the sedimen

关键词： water flow sediment transport pollutant interactions turbulence, adsorption

Iterative Method on Well Bore Boundary in Numerical Modeling of Variably Saturated Flow

在线全文

学校读者我要写书评

暂无评论

Transactions of Tianjin University 2012年第2期18卷 104-111页

作者：王俊黄岁樑 chiu on ng College of Environmental Science and Engineering Nankai University Department of Fundamental Subject Tianjin Institute of Urban Construction Department of Mechanical Engineering The University of Hong Kong

An iterative method was developed for incorporating the well bore boundary into the finite difference model of water flow in variably saturated porous media. Six cases were presented involving groundwater pumping or injection to demonstrate the advantages of the iterative method over the traditional method. For the iterative method, the total flux gradually approached the well discharge and the flux profile was non-uniform. And the iterative method took into account the variation of well bore water table. Compared to the traditional method, the iterative method can simulate the variably saturated flow caused by pumping or injection more realistically.

关键词： iterative method variably saturated flow well bore boundary flux profile

Effect of a Submerged Porous Plate on the Hydroelastic Response of a Very Large Floating Structure

在线全文

学校读者我要写书评

暂无评论

Journal of Marine Science and Application 2018年第4期17卷 564-577页

作者： Harekrushna Behera Trilochan Sahoo chiu-On ng SRM Research Institute and Department of Mathematics SRM Institute of Science and Technology Department of Ocean Engineering and Naval Architecture Indian Institute of Technology Department of Mechanical Engineering The University of Hong Kong

Scattering of oblique flexural-gravity waves by a submerged porous plate in a finite water depth is investigated under the assumptions of linearized surface waves and small-amplitude structural response. The study is carried out using eigenfunction expansions and the corresponding orthogonal mode-coupling relations associated with flexural-gravity waves in uniform water depth. The characteristics of the roots of the complex dispersion relation are examined using the principle of counting argument and contour plot. Characteristics of the flexural-gravity waves are studied by assuming both the floating elastic plate and the submerged porous plate are infinitely extended in horizontal directions. The effectiveness of the submerged porous structure on the reflection, transmission, and dissipation coefficients is analyzed for various wave and structural parameters.

关键词： Flexural-gravity wave Mode-coupling relation Dispersion relation Porous plate Reflection and transmission coefficients