摘要:

Examples from the personal experience of the author are used to illustrate the synergistic ways in which basic and applied research can interact in the field of hydraulics. While maintaining such a joint effort is not always easy, the intellectual rewards can be substantial.

ISSN:0022-1686    

DOI:10.1080/00221689609498482

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A benchmark exercise for multi-dimsional thermohydraulic codes was carried out related to natural convection decay heat removal in liquid metal-cooled fast breeder reactors. A total of twelve computational methods were applied to the benchmark problem which simulated mixed forced and buoyancy driven penetration flow and thermal stratification phenomena. The applicability of turbulence models and higher order schemes of convection terms, was examined, and a combined method incorporating a higher order scheme and a turbulence model was found to be highly effective among the group of finite difference methods. The importance of turbulence models was also recognized for the finite element method. Development of a turbulence model applicable to the mixed convection flow regime was also discussed.

ISSN:0022-1686    

DOI:10.1080/00221689609498483

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The turbulence structure of flows of clay suspensions in smooth-boundary open channels were experimentally studied. Clay suspensions are non-Newtonian fluids. Transition from laminar to turbulent flows occurs when a Reynolds number Remis between 2,000 and 10.000. Three layers can be identified in transitional flows, i.e. a) laminar sublayer, b) turbulent layer, and c) upper layer. In the upper layer the turbulence intensity is low or even equal to zero. The flow between the turbulent layer and the laminar sublayer is alternatively laminar and turbulent. For various concentrations of clay suspension the mean velocity profiles follow the Coles' velocity formula with negative wake parameter and smaller Karman constant. The distribution of turbulence intensity is far more nonuniform than that of water flow. The probability density and autocorrelation coefficient are discussed and it is concluded that the turbulence in the non-Newtonian flow is produced in the turbulent layer and high frequency turbulence is suppressed by the high viscosity and yield stress.

ISSN:0022-1686    

DOI:10.1080/00221689609498484

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Extensive experiments conducted by the writers on fractional bed load transport rates are reported. These data as well as those available from other sources, covering wide range of flow conditions and sediment nonuniformity, have been analysed. Firstly, the semi-theoretical model proposed by Misri et al. (1984) is modified to evolve a method of bed load calculation and finally an empirical relationship is proposed incorporating the several parameters influencing the bed load transport of nonuniform sediments.

ISSN:0022-1686    

DOI:10.1080/00221689609498485

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

HYDRAULIC GATES AND VALVES IN FREE FLOW AND SUBMERGED OUTLETSby Jack Lewin, Thomas Telford Publications, 238 pp, ISBN 0 7277 2020 1

ISSN:0022-1686    

DOI:10.1080/00221689609498486

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A method for predicting the depth-discharge relationship in a compound channel is developed and applied to two different sets of experimental results. The method uses a mixing length formulation to account for the turbulent interaction between the main channel and the floodplain and the resulting momentum exchange. This momentum transfer tends to reduce the discharge in the main channel and increase the discharge on the floodplain. The net effect is a reduction in the overall discharge capacity of the compound channel. As a result, practical methods which can allow for the interaction effect are needed. In this formulation a variation of Prandtl's mixing length hypothesis is applied to calculate the apparent shear stresses, indicative of the turbulent interaction, on the sides of small vertical elements which comprise the compound channel cross-section. The approach suggested is to use the mixing length approximation to calculate the correction for the momentum interaction effects that are neglected when the traditional divided channel approach is used. The traditional divided channel approach referred to herein typically divides the compound channel into three large sub-areas: main channel, left floodplain and right floodplain using a vertical division at the edges of the main channel.

ISSN:0022-1686    

DOI:10.1080/00221689609498487

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A project has recently been undertaken to improve the way in which sewage sludge pipeline systems are designed. A new, more accurate method of calculating pressure losses has been developed which replaces the traditional empirical formulae. The technique uses Computational Fluid Dynamics (CFD) together with the Generalised Bingham Plastic Model to describe the sludge rheology. Improvements have also been made to how the viscometry data is measured and processed. The method has successfully been verified against experimental data and validated against site measurements. Design issues have been addressed and presented in a simple design methodology. Overall, the work has had considerable success, as demonstrated by the fact that the technique is currently being used to design major capital investment schemes.

ISSN:0022-1686    

DOI:10.1080/00221689609498488

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A prediction model for computing the sequent depth ratio of the hydraulic jumps formed in sloping rectangular channel with positive or negative step has been developed. It is based on the application of the one dimensional momentum and continuity equations. The presented model contains two defined parameters. One of them to account for the effect of the channel slope and the second for the presence of the positive or negative step. The model can predict the solely and the combined effects of the bed slope and the step on the sequent depth ratio of the hydraulic jumps. Large series of experimental data have been used to calibrate and verify the developed model for both sloping as well as horizontal floors. The predictions agreed reasonably well with theoretical and experimental results of other authors.

ISSN:0022-1686    

DOI:10.1080/00221689609498489

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

On a stepped channel, two distinct flow regimes may occur : nappe flow for low discharges and flat slopes, andskimming flow for larger flow rates. A simple analytical method to predict the onset of skimming flow is presented.The method is based upon the change of momentum direction at the impact of the jet on the downstreamstep. The results of the analysis are compared with existing experimental data. The onset of skimmingflow is expressed in terms of the initial Froude number and jet angle. The generalisation of the study resultsenables to predict the onset of skimming flow and hence the risk of jet deflection at the first upstream step.

ISSN:0022-1686    

DOI:10.1080/00221689609498490

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

ISSN:0022-1686    

DOI:10.1080/00221689609498491

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor