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Discussion on "Hydraulic parameters in channels with wall vegetation and gravel bed" by Hossein Afzalimehr,Jueyi Sui and Razieh Moghbel[***.,25(2010) 81-90]

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International Journal of Sediment Research 2011年第2期26卷 247-249页

作者： O.YAGCI U.TURKER Istanbul Technical University Civil Engineering FacultyDivision of Hydraulics Near East University Civil Engineering DepartmentDivision of Hydraulics

We discussants appreciate the authors’ investigation on the impacts of the vegetated channel walls and aspect ratio on flow velocity profiles,shear stress distribution and roughness coefficient of *** primary aim of this comment is to emphasize some of the points which were not considered by the authors during their *** discussers would like to mention the following points regarding the paper. The expression of "wall vegetation" is a new term for the current *** the researchers have not given enough explanation about *** is "wall vegetation"?Where can we observe wall-vegetation in nature?What are the characteristic species as "wall-vegetation"?We think that the clarification of this point will significantly improve the benefit of this study.

关键词： Discussion on by Hossein Afzalimehr,Jueyi Sui and Razieh Moghbel[Int.J.Sed.Res Hydraulic parameters in channels with wall vegetation and gravel bed

Modeling the initiation of sediment motion under a wide range of flow conditions using a Geno-Mamdani Fuzzy Inference System method

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International Journal of Sediment Research 2020年第5期35卷 467-483页

作者： Hussein Bizimana Abdüsselam Altunkaynak hydraulics division Faculty of Civil EngineeringIstanbul Technical University

The current study introduces a novel approach to estimate the incipient motion of sediments under a wide range of flow regimes by developing a fuzzy model with a fuzzy-band that refers to a transition from weak motion to general motion of *** partial sediment entrainment is defined by fuzzy sets considering the uncertainty related to the individual ratio of inertia to viscous forces which is the definition of shear Reynolds *** the current study,the Mamdani Fuzzy Inference System（Mamdani FIS） is used to develop a comprehensive fuzzy model of the incipient motion of *** Mamdani FIS has a shortcoming regarding the training of the fuzzy *** estimate the dimensionless shear stress,a new method is developed by combining a genetic algorithm with the fuzzy approach which is named the Geno-Mamdani Fuzzy Inference System（GMFIS） *** performance of the GMFIS model is evaluated using experimental data by considering root mean square error（RMSE）,NashSutcliffe coefficient of efficiency（CE）,degree of robustness（Dr）,and concordance coefficient（CC） as evaluation *** GMFIS model performed very well based on the RMSE,CE,Dr,and CC values and satisfactorily represented the three types of incipient ***,a new range of fuzzy,dimensionless,critical shear stress values is established in all flow conditions from weak to general sediment entrainment.

关键词： Incipient motion Dimensionless shear stress Shear Reynolds number Fuzzy logic Genetic algorithms Sediment

Transient Evolution of Inter Vessel Gap Pressure Due to Relative Thermal Expansion Between Two Vessels

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Journal of Thermal Science 2002年第3期11卷 220-225页

作者： K.Natesan P.Selvaraj P.Chellapandi S.C.Chetal Mechanics and hydraulics division Indira Gandhi Centre for Atomic Research Kalpakkam India

In a typical liquid metal cooled fast breeder reactor (LMFBR), a cylindrical sodium filled main vessel, which carries the internals such as reactor core, pumps, intermediate heat exchangers etc. is surrounded by another vessel called safety vessel. The inter vessel gap is filled with nitrogen. During a thermal transient in the pool sodium, because of the relative delay involved in the thermal diffusion between MV and SV, they are subjected to relative thermal expansion or contraction between them. This in turn results in pressurisation and depressurisation of inter vessel gap nitrogen respectively. In order to obtain the external pressurization for the buckling design of MV, transient thermal models for obtaining the evolutions of MV, SV and inter gap nitrogen temperatures and hence their relative thermal expansion and inter vessel gap pressure have been developed. This paper gives the details of the mathematical model, assumptions made in the calculation and the results of the analysis.

关键词： transient thermal calculation relative thermal expansion LMFBR Runga Kutta method.

Modeling nonstationary extreme wave heights in present and future climates of Greek Seas

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Water Science and Engineering 2016年第1期9卷 21-32页

作者： Panagiota Galiatsatou Christina Anagnostopoulou Panayotis Prinos hydraulics Laboratory Division of Hydraulics and Environmental Research Department of Civil Engineering Aristotle University of Thessaloniki Department of Meteorology and Climatology School of Geology Aristotle University of Thessaloniki

In this study the generalized extreme value （GEV） distribution function was used to assess nonstationarity in annual maximum wave heights for selected locations in the Greek Seas, both in the present and future climates. The available significant wave height data were divided into groups corresponding to the present period （1951-2000）, a first future period （2001-2050）, and a second future period （2051-2100）. For each time period, the parameters of the GEV distribution were specified as functions of time-varying covariates and estimated using the conditional density network （CDN）. For each location and selected time period, a total number of 29 linear and nonlinear models were fitted to the wave data, for a given combination of covariates. The covariates used in the GEV-CDN models consisted of wind fields resulting from the Regional Climate Model version 3 （RegCM3） developed by the International Center for Theoretical Physics （ICTP） with a spatial resolution of 10 km ×10 km, after being processed using principal component analysis （PCA）. The results obtained from the best fitted models in the present and future periods for each location were compared, revealing different patterns of relationships between wind components and extreme wave height quantiles in different parts of the Greek Seas and different periods. The analysis demonstrates an increase of extreme wave heights in the first future period as compared with the present period, causing a significant threat to Greek coastal areas in the North Aegean Sea and the Ionian Sea.

关键词： Wave extremes Climate change Nonstationarity GEV-CDN Principal component analysis

Estimation of Tsunami Run-up Height by Three Artificial Neural Network Methods

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China Ocean Engineering 2009年第1期23卷 85-94页

作者： Nuray GEDIK Emel IRTEM H.Kerem CIGIZOGLU M.Sedat KABDASLI Department of Civil Engineering Balikesir University division of hydraulics Civil Engineering FacultyIstanbul Technical University

Tsunami ran-up height is a significant parameter for dimensions of coastal structures. In the present study, tsunami run-up heights are estimated by three different Artificial Neural Network （ANN） models, i.e. Feed Forward Back Propagation （FFBP）, Radial Basis Functions （RBF） and Generalized Regression Neural Network （GRNN）. As the input for the ANN configuration, the wave height （H） values are employed. It is shown that the tsunami ran-up height values are closely approximated with all of the applied ANN methods. The ANN estimations are slightly superior to those of the empirical equation. It can be seen that the ANN applications are especially significant in the absence of adequate number of laboratory experiments. The results also prove that the available experiment data set can be extended with ANN simulations. This may be helpful to decrease the burden of the experimental studies and to supply results for comparisons.

关键词： tsanami run-up height artificial neural network methods experiments

Predicting characteristics of dune bedforms using PSO-LSSVM

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International Journal of Sediment Research 2017年第4期32卷 515-526页

作者： Kiyoumars Roushangar Seyed Mahdi Saghebian Dominique Mouaze division of hydraulics Department of Civil EngineeringUniversity of Tabriz Morphodynamic Laboratory University of Caen

Dunes have a large influence on hydraulic roughness, and, thereby, on water levels which could affect the navigability of rivers and performance of hydraulic structures. The present study investigated the variation of geometric and topographic characteristics of dune bedforms and flow features as measured in laboratory studies(data sets from laboratory experiments) to estimate the roughness coefficient and characteristics of dune height. The Least Squares Support Vector Machine(LSSVM), which was optimized using Particle Swarm Optimization(PSO), was used as the Meta model approach to predict the values of interest. Developed models were separated into three categories: modeling using flow characteristics,modeling of flow and bedform characteristics, and modeling by using flow and sediment *** was found that for estimation of the roughness coefficient in open channels with dune bedforms,models developed based on flow and sediment characteristics performed more successfully. The model with input parameters of flow and grain Reynolds numbers(Re and R, respectively) and the ratio of the hydraulic radius(R) to the median grain diameter(D) yields a squared correlation coefficient(R2) of0.8609, a coefficient of determination(DC) of 0.7361,and a root mean square error(RMSE) of 0.0034 for a test series of Manning’s roughness coefficient which was the most accurate model. Results proved the key role of flow Reynolds number(Re) values as an input feature for all models predicting the roughness coefficient. Accordingly, classic approaches led to poor results in comparison. On the other hand, results obtained for estimated values of relative dune height led to moderate prediction quality, which albeit,outperformed classic approaches.

关键词： Alluvial channel Hydraulic characteristics Dune Roughness coefficient Least Squares Support Vector machine Particle Swarm Optimization

Linear and non-linear approaches to predict the Darcy-Weisbach friction factor of overland flow using the extreme learning machine approach

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International Journal of Sediment Research 2018年第4期33卷 415-432页

作者： Kiyoumars Roushangar Saba Mirza Alipour Dominique Mouaze division of hydraulics Department of Civil Engineering University of Tabriz Morphodynamic Laboratory University of Caen

In modeling of overland flow and erosion, the overland flow friction factor(f), is a crucial factor. Due to the importance of a good understanding of f and its variability, the current study aimed to investigate the capability of non-linear approaches to estimate the Darcy-Weisbach friction factor of overland flow and its components(sediment transport, wave, form, and grain friction factors) through the Extreme Learning Machine(ELM) approach. Four datasets were used herein which were obtained from flume experiments done by different researchers. In order to investigate the effects of different parameters on the friction factor, numerous models consisting of various parameters were utilized to predict the friction factor using the ELM approach. The modeling procedure was established in two stages; the first stage aimed to model the overland flow friction factor and investigate the effect of the different parameters on the friction factor using non-linear separation via the ELM approach. In the second stage, the friction factor was linearly separated into different types of friction factors and then the separate components were estimated. Sensitivity analysis results confirmed the key role of Froude number(Fr) values for most of the models. On the other hand, the results obtained for estimated values of the friction factor were acceptable and outperformed available empirical approaches.

关键词： Overland flow Extreme Learning Machine(ELM) Friction factor Sediment transport friction factor Wave friction factor Grain friction factor Form friction factor

Boundary layer influence on ship model tests in extremely shallow and confined water

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Journal of Hydrodynamics 2023年第2期35卷 365-378页

作者： Evert Lataire Asif Raza Marc Vantorre Guillaume Delefortrie Maritime Technology division Ghent UniversityGhentBelgium ANAST University of LiègeLiègeBelgium Flanders hydraulics Research AntwerpBelgium

Ships sailing in shallow and/or confined water(when calling a harbour or other berthing areas),will experience a different behaviour due to the interaction with vertical and/or horizontal *** other hydrodynamic changes induced in confined water,the lateral ship-bank interaction force changes its sign at a critical distance between ship and bank or ***,this distance and its effects on model test results have not been quantified in the *** investigate the shallow water hydrodynamics coupled with bank effects,systematic model tests were carried out at Flanders hydraulics Research(FHR)with different ship *** following parameters were systematically varied:water depth,lateral position,speed,and propeller *** change of the ship-bank induced lateral force from an attraction force in medium-deep and shallow water to a repulsion force in extremely shallow water conditions,can be ascribed to the interaction of the boundary layers of the ship model and the environment(tank and installed banks).In this article,a mathematical model is proposed for the critical distance in terms of boundary layer influence *** indicates the range where the model tests are influenced by the horizontal or vertical restrictions combined with the propeller’s dynamic ***,the expression has also been extended to describe the relationship between full-scale ship length and water depth with the boundary layer influence *** to lower Reynolds numbers and relatively thicker boundary layers at model scale,upscaling of the model test results,according to Froude’s law,may provide erroneous *** influence of the boundary layer initiates at a relatively higher under keel clearance(UKC)for a smaller ship model compared with a larger ship ***,the boundary layer’s influence with respect to ship model length should be considered during model testing.

关键词： Shallow water hydrodynamics bank effects boundary layer model tests mathematical model

Dynamic Responses of Block Type Quay Walls Under Cyclic Loading

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China Ocean Engineering 2021年第2期35卷 281-290页

作者： Hulya Karakus CIHAN Kubilay CIHAN Yuksel Project 06610 CankayaAnkaraTurkey Civil Engineering Department Hydraulics DivisionKırıkkale UniversityKırıkkaleTurkey

The purpose of this research is to study the dynamic responses of gravity quay walls with block type consisting of“three blocks”*** this purpose,1g shaking table tests were conducted under different cyclic loadings for two different saturated granular backfill materials(Soil 1 and Soil 2).In this study,D_(n50) of Soil 1 and Soil 2 are selected as 2.2 cm and 1.0 cm,*** the experiments,accelerations,soil pressures and displacements were measured for each *** results pointed out that Soil 2 caused more damage on *** measurements for displacement and tilting of each block were discussed in view of“acceptable level of damage in performance-based design”given in PIANC(2001).The result of the study showed that the definitions of damaged levels given in PIANC(2001)were reliable for using in performance-based methods for seismic design of block type quay walls.

关键词： block type quay walls 1g shaking table tests damage level dynamic response