摘要:

The optimal control of hydraulic networks often necessitates making a considerable number of very rapid simulations of flows, such as is not practical using existing, computationally-demanding, numerical-hydraulic models. However, the site-specific knowledge and data that is encapsulated in any such numerical model can be encapsulated in its turn in an artificial neural network (ANN), and this can provide much faster simulations. In this study, a number of possible types and configurations of ANNs are investigated for their suitability to this class of application. When regarded from a hydroinformatics point of view, this study becomes one of identifying the most suitable ANN encapsulations of numerical-hydraulic encapsulations of generic hydraulic knowledge and site-specific data.

ISSN:0022-1686    

DOI:10.1080/00221689909498303

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A complete three-dimensional finite difference scheme has been developed to analyze the earthquake-induced nonlinear hydrodynamic pressures on inclined dam faces with arbitrary reservoir shapes. Both the free surface waves and the nonlinear convective acceleration were included in the analysis. Numerical experiments have been made to determine the desirable mesh arrangements and time increments. The computational accuracy were assured by checking both mass and momentum balance at each time step. The effects of the arbitrary dam-reservoir system on dam hydrodynamics are systematically studied by analyzing the dam-reservoir system with various dam shapes, sloped reservoir banks and uneven reservoir bottoms. For a rectangular reservoir and excited byx-component ground acceleration, the three-dimensional analysis can be simplified by a twodimensional analysis and the results are independent of the reservoir width. By arbitrary acting direction of ground motion, the fluid near the abutment is excited both byx-component andz-component of ground acceleration, the combination of the two-way action results in the variation of the hydrodynamic pressure distribution on dam face. The dynamic effects on the hydrodynamic pressure increase as the reservoir width does, but this increase becomes negligible when the reservoir width is larger than four times of water depth. The compressibility of water is important in dam-hydrodynamic analysis, but it is truly problem dependent.

ISSN:0022-1686    

DOI:10.1080/00221689909498304

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Water and sediment flow was modelled numerically in three dimensions in a tunnel-type sand trap. The numerical model solved the transient Navier-Stokes equations with thek-ε turbulence model. Simultaneously, the sediment flow was calculated by solving the transient convection-diffusion equation for sediment concentration. Multiple sediment sizes were used. Van Rijn's formula for sediment concentration was used as boundary condition for the bed. Sediment continuity for the cells close to the bed gave the bed changes with time. An adaptive grid was used, adjusting to the bed changes. The processes in the sand trap involved both sedimentation and erosion, as a large volume of sand was formed and moved through the geometry. A physical model test was carried out to verify the numerical model. Bed levels were measured at a longitudinal profile and a cross-section. The results from the physical and numerical model compared well.

ISSN:0022-1686    

DOI:10.1080/00221689909498305

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The nonlinear mathematical model for depth-averaged flow allows for discontinuous solutions that correspond with the dynamic behaviour of rapid changes in flow. Such discontinuities, that can fundamentally affect the predicted morphological response of a river, are analyzed theoretically and numerically. Hereto, the entropy conditions as defined by Lax and the Rankine-Hugoniot or shock relations are used to analyze propagation rates and stability. Apart from subcritical and supercritical flows, a transition regime can be identified for flows with mobile beds.

ISSN:0022-1686    

DOI:10.1080/00221689909498306

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

First-order approximation techniques for estimating stochastic parameters of a sediment transport model are presented. The non-homogeneous compound Poisson model of Shen-Todorovic eliminating certain idealized assumptions to describe the movement of sediment in natural streams is a revision of the earlier homogeneous model of Einstein-Hubbell-Sayre. However, the complexity of the non-homogeneous model and the difficulty in determining the model parameters has limited its application. The proposed approximation techniques employ the first-order Taylor expansions, with respect to a selected temporal or spatial point by a finite difference, of the cumulative probability distribution function (CDF) of particle displacements. The first-order expansions are divided by the original CDF for further simplification. The simplified forward- and backwardexpansions are numerically solved as a system to evaluate the parameter at the specified point. The non-homogeneous parameters are pursued with successive applications of this procedure to various points. An example of sediment infiltration into the gravel column is provided showing the procedures of parameter estimation and the verification of results. Temporal and spatial variations of the parameters are also discussed.

ISSN:0022-1686    

DOI:10.1080/00221689909498307

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

An equation for high concentration granular flow is presented. The equation contains viscous and impact coefficients, which have been determined. The viscous coefficient is a constant. The impact coefficient has been correlated to properties of the solid and fluid. The equation agrees reasonably well with several sets of experiments by different investigators covering a wide range of granular flows.

ISSN:0022-1686    

DOI:10.1080/00221689909498308

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The Reichardt hypothesis on the lateral transport of momentum has been used previously to predict the velocity field of multiple turbulent jets. In this paper, based on an extension of the Reichardt hypothesis to the lateral transport of pollutant, a method has been developed to predict the concentration field of multiple circular turbulent jets discharged into a large stagnant ambient. Experimental observations from one experiment with three parallel jets support the theoretical predictions.

ISSN:0022-1686    

DOI:10.1080/00221689909498309

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Choi (1998) proposed a finite element model for the simulation of turbidity currents spreading two-dimensionally in deep ambient water. The dissipative-Galerkin formulation was used for the hyperbolic feature of the governing equations. Accurate front tracking was accomplished by employing the deforming grid generation technique. In the present paper, mass conservative property of the two-dimensional numerical method is tested in the case of a buoyancy-conserving saline current. Sensitivity analyses are also performed to see the model response to such parameters as total buoyancy flux, inlet velocity, flow resistance co-efficient, slope, and sediment particle. Finally, laboratory experiments are conducted by generating saline density currents for the verification of the numerical model. The experimental data are obtained with an emphasis on bulk characteristics of the density current such as propagating pattern, longitudinal and lateral spreading distances, and opening angle. The observed result appears to be in a good agreement with the computed solution, which suggests that the developed numerical model is capable of simulating the turbidity current propagating on a slope with no lateral restriction.

ISSN:0022-1686    

DOI:10.1080/00221689909498310

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

ISSN:0022-1686    

DOI:10.1080/00221689909498311

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

ISSN:0022-1686    

DOI:10.1080/00221689909498302

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor