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A Model for Temperature Infl uence on Concrete Hydration Exothermic Rate (Part one: Theory and Experiment)

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Journal of Wuhan University of Technology(Materials Science) 2014年第3期29卷 540-545页

作者：朱振泱 QIANG Sheng CHEN Weimin Hydrochina Huadong Engineering Corporation college of water conservancy and hydropower Engineering Hohai University

Recent achievements in concrete hydration exothermic models based on Arrhenius equation have improved computation accuracy for mass concrete temperature field. But the properties of the activation energy and the gas constant （Ea/R） have not been well studied yet. From the latest experiments it is shown that Ea/R obviously changes with the hydration degree without fixed form. In this paper, the relationship between hydration degree and Ea/R is studied and a new hydration exothermic model is proposed. With those achievements, the mass concrete temperature field with arbitrary boundary condition can be calculated more precisely.

关键词： hydration exothermic model Arrhenius equation activation energy hydration degree temperature rise model

Crack status analysis for concrete dams based on measured entropy

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Science China(Technological Sciences) 2016年第5期59卷 777-782页

作者： WU Bang Bin WU Zhong Ru CHEN Bo SU Huai Zhi BAO Teng Fei WANG Shao Wei State Key Laboratory of Hydrology-water Resources and Hydraulic Engineering Hohai University college of water conservancy and hydropower Engineering Hohai University

The integrity and safety of concrete darns are seriously affected by the existing cracks in dam bodies, and some serious cracks may cause dam failure or disaster. The propagation of cracks in concrete dams is accompanied by changes in energy distribution, which can be represented by changes in the structure＇s system entropy. Therefore, the entropy theory can be used in analyzing the behavior of dam cracks. Due to the randomness and locality of crack propagation, it is difficult to predict the loca- tion of cracks by traditional monitoring methods. To solve this problem, the influence of spatial positions of monitoring points on inspection zones is represented by a weight index, and the weight index is determined by the distance measure method proposed in this paper. Through the weighted linear fusion method, the entropy of multiple monitoring points is obtained for analyzing the behavior of dam cracks in the selected zones. Meanwhile, the catastrophe theory is used as the variation criterion of an entropy sequence in order to predict the instability time of dam cracks. Case studies are put forward on a high arch darn, and the fusion entropy is calculated according to the monitoring data from strain gauges. Results show that the proposed method can effectively predict the occurrence time and location of dam cracks regardless of the layout of monitoring instruments, and it is a new way to analyze the occurrence and propagation of dam cracks.

关键词： energy measured data entropy changes multiple monitoring points fusion concrete dam

Mixing of A Non-Circular Jet into A Counterflow

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China Ocean Engineering 2015年第1期29卷 91-104页

作者：李志伟肖洋唐洪武 State Key Laboratory of Hydrology-water Resources and Hydraulic Engineering Hohai University college of water conservancy and hydropower Engineering Hohai University

An elliptic jet and a square jet flowing into a counterflow with different jet-to-current velocity ratios are investigated by using realizable Ice model. Some computed mean velocity and scalar features agree reasonably well with experimental measurements, and more features are obtained by analyzing the computed results. After fluid issues from a nozzle, it entrains ambient fluid, and its velocity and concentration on the centerline decay with the distance downstream from the potential core （10）. The decay ratio increases with the decreasing jet-to-current velocity ratio a. For an elliptic jet, the evolution of the excess velocity half-width b and the concentration half-width be merely remains constant near the jet exit on major-axis plane while they increase linearly on the minor-axis plane. However, the half-widths on the major-axis and minor-axis plane become proportional to the axial distance downstream after equaling each other. For a square jet, b and bc increase linearly with the distance downstream from the jet exit, but the spread ratio is larger on the middle plane than that on the diagonal plane before they equal each other. The radial extent of the dividing streamline r~ or the mixing boundary rs~ increases linearly downstream, and decreases exponentially after reaching a peak at Xb. The ratio on the minor-axis plane is larger than that on the major-axis plane for an elliptic jet. The characteristics are the same for the square jet. b, be, rs, and rsc on two corresponding planes become equal to each other more rapidly for the square jet than for the elliptic jet, because the sharp comer of the square nozzle induces secondary structures that are more intense. The distributions of the excess axial velocity and scalar concentration exhibit self-similarity for either the elliptic jet or square jet in the region of 10 〈 x 〈 xb. On the cross section, four counter-rotating pairs of vortices, which enhance the entrainment between the jet and counterflow, form at

关键词： counterflow excess velocity scalar concentration penetration length radial extent

FRACTIONAL-STEP FINITE ELEMENT METHOD FOR CALCULATION OF 3-D FREE SURFACE PROBLEM USING LEVEL SET METHOD

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Journal of Hydrodynamics 2006年第6期18卷 742-747页

作者： ZHAO Lan-hao LI Tong-chun WANG Ling HERREROS M. I. PASTOR M. college of water conservancy and hydropower Engineering Hohai University Naniing 210098 China Anhui Survey and Design Institute of water conservancy and hydropower Hefei 230022 China CEDEX and E.T.S. de Caminos Madrid Spain

A two-step Taylor-Galerkin fractional-step finite element method, which is of second order accuracy in space and time, was proposed for the three-dimensional free surface problem. With this method, the intermediate velocity was explicitly obtained by neglecting pressure gradient term, and then the velocity was corrected by adding the effects of pressure once the pressure field had been obtained from the pressure Poisson equation. The level set approach was applied to track implicitly the free surface. In order to track the free surface, the transport equation of the level set function was solved at each time step and the level set function is reinitialized through iteration to maintain it as a distance function. The governing equations of the system were discretized by the two- step Taylor-Galerkin method, which is of high-order accuracy and easy to be used. The validity and reliability of this method in this article were proved by two numerical examples.

关键词： level set free surface two steps Taylor-Galerkin fractional step FEM

Uncertainty and Sensitivity Analyses of the Simulated Seawater—Freshwater Mixing Zones in Steady-State Coastal Aquifers

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China Ocean Engineering 2015年第4期29卷 489-502页

作者：赵忠伟赵坚辛沛华国芬金光球 State Key Laboratory of Hydrology-water Resources and Hydraulic Engineering Hohai University college of water conservancy and hydropower Engineering Hohai University

The uncertainty and sensitivity of predicted positions and thicknesses of seawater-freshwater mixing zones with respect to uncertainties of saturated hydraulic conductivity, porosity, molecular diffusivity, longitudinal and transverse dispersivities were investigated in both head-control and flux-control inland boundary systems. It shows that uncertainties and sensitivities of predicted results vary in different boundary systems. With the same designed matrix of uncertain factors in simulation experiments, the variance of predicted positions and thickness in the flux-control system is much larger than that predicted in the head-control system. In a head-control system, the most sensitive factors for the predicted position of the mixing zone are inland freshwater head and transverse dispersivity. However, the predicted position of the mixing zone is more sensitive to saturated hydraulic conductivity in a flux-control system. In a head-control system, the most sensitive factors for the predicted thickness of the mixing zone include transverse dispersivity, molecular diffusivity, porosity, and longitudinal dispersivity, but the predicted thickness is more sensitive to the saturated hydraulic conductivity in a flux-control system. These findings improve our understandings for the development of seawater-freshwater mixing zone during seawater intrusion processes, and give technical support for groundwater resource management in coastal aquifers.

关键词： seawater intrusion mixing zone uncertainty analysis fractional factorial design Morris "s OAT design coastal aquifer

PREDICTION OF STAGE-DISCHARGE IN RIVER USING KALMAN FILTER

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Journal of Hydrodynamics 1991年第1期3卷 51-55页

作者： Fan, Yu-chen water conservancy and hydropower Research Inst Beijing China

In this paper Mannig's resistance coefficient n is used as a state-variable for Kalman filter, the stage h in the river as an observation-variable. Comparing this form of Kalman filter with Simons' form, the result of... 详细信息

关键词： Computers Applications Flow of water Hydrodynamics Mathematical Models Mathematical Techniques Differential Equations

Flow regime and energy dissipation of SFS-type flip buckets

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Journal of Hydrodynamics 2020年第1期32卷 179-182页

作者： Ran Tian Jian-hua Wu Fei Ma college of water conservancy and hydropower Engineering.Hohai University Nanjing 210098China

In the present work,a slot-type flip bucket with separated flows,called SFS-type flip bucket,is developed,and flow regime and energy dissipation are experimentally *** with the circular-shaped or slot-type flip bucket buckets,the present SFS-type flip bucket has better flow regime and larger energy dissipation since the three branches of the flows are separated through the outlet of the flip ***,the energy dissipation for this flip bucket is estimated.

关键词： Energy dissipation flow region separated flow SFS-type flip bucket

PREDICTION OF OCEANIC DATA

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China Ocean Engineering 1989年第3期4卷 353-364页

作者： Fan, Yuchen water conservancy and hydropower Research Inst China

The Kalman filter is used to predict the velocity of littoral current, the wave direction, the sea depth and the wave steepness. In this paper the Kazumasa model has been modified to deal with two cases: 1) For the positions a bit far from the shore, the interaction between the velocity of littoral current as well as the wave direction and the sea depth as well as the wave steepness must be considered. 2) For the positions very close to the shore, three new parameters describing the asymmetry wave are introduced to deal with wave breaking. The results from the modified model are compared with observed data, and the comparison indicates that the modified model is better and capable of giving more accurate results.

关键词： Coastal Engineering Flow of water Mathematical Models Hydrodynamics Mathematical Models Signal Filtering and Prediction Kalman Filtering water Waves

Numerical study of AE and DRA methods in sandstone and granite in orthogonal loading directions

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water Science and Engineering 2012年第1期5卷 93-104页

作者： Xu-hua REN Hai-jun WANG Ji-xun ZHANG college of water conservancy and hydropower Engineering Hohai UniversityNanjing 210098China

The directional dependency of the acoustic emission （AE） and deformation rate analysis （DRA） methods was analyzed, based on the contact bond model in the two-dimensional particle flow code （PFC2D） in two types of rocks, the coarse-grained sandstone and Aue granite. Each type of rocks had two shapes, the Brazilian disk and a square shape. The mechanical behaviors of the numerical model had already been verified to be in agreement with those of the physical specimens in previous research. Three loading protocols with different loading cycles in two orthogonal directions were specially designed in the numerical tests. The results show that no memory effect is observed in the second loading in the orthogonal direction. However, both the cumulative crack number of the second loading and the differential strain value at the inflection point are influenced by the first loading in the orthogonal direction.

关键词： Kaiser effect deformation rate analysis PFC2D orthogonal loading directions in situ stress measurement