摘要:

Modern thermal or nuclear plants need cooling water from river or sea. Therefore an intake pond for the water delivery system is a requisite component where sediment frequently deposits. An impinging jet is a functional measure for sediment re-suspension and a precaution against sediment deposition. This paper predicts the consequences of this new measure using theoretical analysis and laboratory experiments. The jet diffusion discharged into an ambient flow field, and the jet velocity at bottom, are predicted by the governing equations using an integral method. Equilibrium scour is obtained after the process of scour asymptotically finished for a limited depth sand layer. The non-dimensional equation derived can predict well the particle re-suspension. Critical jet condition is obtained for the sediment re-suspension by experiments. The effect of the jet angle and jet height on sediment re-suspension is also included and discussed. The results obtained for the scour to a limited sand bed by an impinging jet through cross flow is especially significant to the engineering design of intake ponds and culverts etc.

ISSN:0022-1686    

DOI:10.1080/00221680009498313

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The results of experimental investigations indicate that sand wavelets can be generated from plane-bed conditions in open-channel laminar flow, the lengths, shapes and patterns of generation for these wavelets being consistent with observations for alluvial flows. Wavelets are of a preferred wavelength which is relatively insensitive to the characteristics of the applied flow and primarily a function of the size of the sediment, these wavelengths λ for alluvial and laminar open-channel flows over beds of quartz and lightweight sediments of sized= 0.2 mm tod= 1.6 mm being simply described by λ = 175d0.75, where λ anddare expressed in millimetres. The laminar-flow sand-wavelet data present significant implications to contemporary understanding of bed-form mechanics, with both ripples and dunes being postulated to subsequently develop from these wavelets for alluvial flows. The data also raise significant questions as to whether the generation of ripples and dunes in alluvial flows can be attributed to an organised structure of turbulence within the flow.

ISSN:0022-1686    

DOI:10.1080/00221680009498314

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The Central Platte River often experiences high water temperatures during sunny, hot summer days. A 128-km reach of the Platte River downstream of two hydropower dams (Kingsley Dam and North Platte/Keystone Diversion Dam) was studied to determine the relationship between river summer water temperatures and river flow-rate, and the impacts of in-stream flow requirements upon peak water temperatures. This reach serves as a habitat for eight federally listed or endangered species, as well as over 300 species of migratory birds, including 500,000 sandhill cranes and 7-9 million ducks and geese. Hourly water temperatures were simulated using a dynamic numerical model (MNSTREM) with and without in-stream flow requirements. It was found that a clear relationship exists between river water temperatures and river flow-rate. In addition, it was found that the occurrence of high water temperatures can be attributed to low river flow-rate and can be reduced, but not eliminated, with minimum in-stream flow requirements.

ISSN:0022-1686    

DOI:10.1080/00221680009498315

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Some fundamental topics of the compressibility influence of the extra-high-velocity aerated water flow in hydraulic engineering are studied in the present paper. A closed system of the simplified basic equations of the aerated water flow is deduced using the two-fluid model. A general formula of the sound velocity in the aerated water flow is derived using the sound analysis. It is found that the Wood adiabatic sound formula is a good approximation for calculating the sound velocity in the aerated water flow. Using the analysis of the order of the magnitude, it is found that the compressibility is important in the following cases. 1) The sound motion in the aerated water flow. 2) The aerated water flow with extra great depth. 3) The steady extra-high-velocity aerated water flow in which the mixture velocity is of the order of the sound velocity in it. It is shown that the adiabatic Mach number may act as the compressibility criterion in the steady aerated water flow. For the case of the steady homogeneous aerated water flow, a detailed compressibility standard is obtained, which is just the same as that in aerodynamics.

ISSN:0022-1686    

DOI:10.1080/00221680009498316

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

ISSN:0022-1686    

DOI:10.1080/00221680009498317

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Three implicit high-resolution total variation diminishing (TVD) schemes are presented for solving the Saint-Venant equations. The applicability, performance and validity of these methods are investigated. Recently created benchmark solutions are reproduced for a wide range of cases, which include friction, nonuniform bed slopes, transitions between subcritical and supercritical flow, nonprismatic cross sections and hydraulic jumps. The tests produce satisfactory results without resorting to excessively fine grids. All the methods also produce satisfactory results for an idealized dambreak problem.

ISSN:0022-1686    

DOI:10.1080/00221680009498318

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The one-dimensional groundwater flow equations are coupled with the St. Venant equations to simulate the flow resulting from a sudden removal of a dam over an initially dry downstream bed. The St. Venant equations are solved using a Petrov-Galerkin finite element scheme, while the groundwater flow equations are solved using the Bubnov-Galerkin finite element scheme. The comparison of the computed water surface and discharge per unit width profiles with the corresponding analytical solutions, for a dambreak over frictionless horizontal bed, show that the model possesses excellent phase accuracy, for both positive and negative waves, and can predict the discharge distribution accurately. Also, the computed water surface profiles are compared with the available measured data for the dambreak flows over smooth and rough surfaces of horizontal and sloping channels. In addition, the results obtained from only the St. Venant equations with minimum depth criteria are presented for comparison with the above model.

ISSN:0022-1686    

DOI:10.1080/00221680009498319

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Bed-load transport at high shear stress is numerically simulated with the aid of the two-phase flow model, in which Euler-Lagrange coupling of the governing equations of the fluid and sediment phases are implemented. Fluid phase is described by the vertically two-dimensional k-e turbulence model in unidirectional flow condition, while the sediment motion is expressed by the numerical tracing of the saltating particles. The fluid/particle interaction, as the main interaction mechanism, is explicitly introduced into the governing equations in the present model. The characteristics of the mean-flow velocity profile of the saltation dominant flow, namely two-layer profile, is reproduced well with the present model. Experimental results show the existence of the three-layer type velocity profile under the high bottom shear, while the present model cannot reproduce such characteristics. The limitation of the assumption in the present model by neglecting the existence of the interparticle collision will be discussed on the basis of the results of the simulation.

ISSN:0022-1686    

DOI:10.1080/00221680009498320

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

This technical note presents a simple method for the real time measurement of bed shear stress with a LabView Program for turbulent flow over uniformly rough boundaries, based on the classical logarithmic velocity distribution equation. The method is based on a step-wise linearization of the additive coefficient in the classical logarithmic velocity distribution equation.

ISSN:0022-1686    

DOI:10.1080/00221680009498321

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

ISSN:0022-1686    

DOI:10.1080/00221680009498312

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor