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Numerical investigation on critical length of impermeable plate below underwater pipeline under steady current

Science China(Technological Sciences) 2013年第6期56卷 1232-1240页

作者： ZHANG ZhiYong SHI Bing GUO YaKun YANG LiPeng College of Engineering Ocean University of China School of Engineering University of Aberdeen

This study proposes a new approach in which an impermeable plate is placed under the pipeline to prevent the local scour around the *** order to understand the performance of this approach,the finite volume method(FVM) and volume of fluid(VOF) method are adopted to simulate the flow field around the *** pressure distribution along the sandy bed surface is obtained by considering the variation of water ***,the effects of water depth,unidirectional and bidirectional impermeable plates on pressure difference are *** seepage flow field of sandy bed near underwater pipeline is numerically simulated using the laminar and porous media *** this basis,the effect of the impermeable plate length on hydraulic gradient is investigated and the critical length of impermeable plate is *** simulated results show that when the water depth is smaller than 5.00D(D is the diameter of pipeline),the effect of the water depth on the pressure difference is *** pressure differences between two endpoints of both the unidirectional and bidirectional plates decrease with the increase of the plate *** variations of the pressure differences for both the unidirectional and bidirectional plates are *** the increase of plate length,the hydraulic gradient decreases and the piping at the seepage exit is avoided effectively as long as it reaches a certain *** a critical length of the plate decreases with the increase of the water *** water depth is larger than 4.00D,the effect of the water depth on the critical length is *** the same water depth,the critical length of impermeable plate increases with the increase of the dimensionless flow *** simulation results are in good agreement with the available experimental measurements.

关键词： underwater pipeline steady current impermeable plate numerical simulation critical length

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A new alternative approach for investigating acidization dissolution front propagation in fluid-saturated carbonate rocks

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Science China(Technological Sciences) 2017年第8期60卷 1197-1210页

作者： ZHAO ChongBin HOBBS Bruce ORD Alison Computational Geosciences Research Centre Central South University School of Earth and Environment The University of Western Australia

The natural phenomenon associated with the chemical dissolution of dissolvable minerals of rocks can be employed to develop innovative technology in mining and oil extracting engineering. This paper presents a new alternative approach for theoretically dealing with chemical dissolution front （CDF） propagation in fluid-saturated carbonate rocks. Note that the CDF is represented by the porosity front in this study. In this new approach, the porosity, pore-fluid velocity and acid concentration are directly used as independent variables. To illustrate how to use the present new approach, an aeidization dissolution system （ADS） consisting of carbonate rocks, which belongs to one of the many general chemical dissolution systems （CDSs）, is taken as an application example. When the acid dissolution capacity （ADC） number （that is defined as the ratio of the volume of the carbonate rock dissolved by an acid to that of the acid） approaches zero, the present new approach can be used to obtain analytical solutions for the stable ADS. However, if the ADC number is a nonzero finite number, then numerical solutions can be only obtained for the ADS, especially when the ADS is in an unstable state. The related theoretical results have demonstrated that：（1） When the ADS is in a stable state and in the case of the ADC number approaching zero, the present new approach is mathematically equivalent to the previous approach, in which the porosity, pore-fluid pressure and acid concentration are used as independent variables. However, when the ADS is in an unstable state, the use of the present new approach leads to a free parameter that needs to be determined by some other ways. （2） The existence of a non-step-type dissolution front within a transient region should at least satisfy that none of the ADC number, injected acid velocity and reciprocal of the dissolution reaction rate is equal to zero in the stable ADS.

关键词： acidization dissolution front propagation critical length alternative approach critical time carbonate rocks

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THEORETICAL MODEL ON INTERFACE FAILURE MECHANISM OF REINFORCED CONCRETE CONTINUOUS BEAM STRENGTHENED BY FRP

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Acta Mechanica Solida Sinica 2009年第2期22卷 161-170页

作者： Hong Yuan Zifeng Lin MOE Key Lab of Disaster Forecast and Control in Engineering Institute of Applied Mechanics Jinan University Guangzhou 510632 China

Fiber reinforced polymer （FRP） composites are increasingly being used for the re-pair and strengthening of deteriorated concrete structural components through adhesive bonding of prefabricated strips/plates and the wet lay-up of fabric. Interfacial bond failure modes have attracted the attention of researchers because of the importance. The objective of the present study is to analyse the interface failure mechanism of reinforced concrete continuous beam strength-ened by FRP. An analytical solution has been firstly presented to predict the entire debonding process of the model. The realistic bi-linear bond-slip interfacial law was adopted to study this problem. The crack propagation process of the loaded model was divided into four stages （elastic,elastic-softening,elastic-softening-debonded and softening-debonded stage）. Among them,elastic-softening-debonded stage has four sub-stages. The equations are solved by adding suitable stress and displacement boundary conditions. Finally,critical value of bond length is determined to make the failure mechanism in the paper effective by solving the simultaneously linear algebraic equations. The interaction between the upper and lower FRP plates can be neglected if axial stiffness ratio of the concrete-to-plate prism is large enough.

关键词： FRP interface bond-slip law critical length continuous beam ultimate load

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EFFECT OF SKIN FRICTION ON THE DIRECTIONAL STABILITY OF DRIVEN PILES DURING DRIVING

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Applied Mathematics and Mechanics(English Edition) 1992年第12期13卷 1143-1148页

作者：沈锡英高大钊 Geotechnical Engineering Department of Tongji University Shanghai

In this paper, the driving forces at a pile top are considered as a periodic load during driving and the Mathieu equation is derived. From the stability charts of this equation, we can obtain the critical length of th... 详细信息

关键词： pile skin friction directional stability Mathieu equation critical length

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Some Observations on Bridges Dynamic Behaviour

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Journal of Civil Engineering and Architecture 2020年第3期14卷 144-152页

作者： Jan B.Obrebski Faculty of Civil Engineering Warsaw University of TechnologyAl.Armii Ludowej 16Warsaw 00-637Poland

The paper presents rather some conclusions from large investigations over dynamic behaviour of bridges under travelling loads. There, as basic tool was applied the 3D-Time Space Method (3D-TSM) in edition proposed by present author. The method uses four-dimensional space, where besides of usual 3D space, the time is the fourth dimension. The bridge with simply supported steel girder is here modelled by means of theory for thin-walled bars (TWBs). In final calculations, solutions are obtained here on numerical way applying well known and simple Finite Differences Method (FDM). In consequence the task is brought to trivial determination of unknowns from set of linear algebraic equations. There, essential part of these equations is so called dynamical stiffness matrix (DSM). The last is additionally tested by Uniform Criterion (...) for evaluation of bridges critical States (CrS).

关键词： Bridges dynamic behaviour critical states critical velocity critical length uniform criterion 3D-time-space method

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Quenching for Degenerate Semilinear Reaction-diffusion Systems

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Chinese Quarterly Journal of Mathematics 2008年第2期23卷 276-283页

作者： LI Mei Department of Applied Mathematics Nanjin9 University of Finance and Economics Nanjing 210003China

In this paper, the initial boundary value problem of semilinear degenerate reaction-diffusion systems is studied. The regularization method and upper and lower solutions technique are employed to show the existence and continuation of a positive classical solution. The location of quenching points is found. The critical length is estimated by the eigenvalue method.

关键词： quenching classical solution global solution critical length degeneration

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