摘要:

New formulae for efficiency scaling-up from model to prototype of a hydraulic turbine are presented based on the theoretical analysis that considers the only friction losses through the turbine. Two formulae are presented; one is the precise conversion formula, and the other the simplified practical one. The former can precisely decide the prototype efficiency from the model performance considering the relative friction loss corresponding to the respective Reynolds number and surface roughness in the individual flow passages of the model and prototype turbines, respectively. The latter simplify the precise formula by using a relative total friction loss that can be assumed constant irrespective of type of machines and specific speed, instead of the individual friction losses through the turbine. The new formulae need not the classical loss distribution coefficient V.

ISSN:0022-1686    

DOI:10.1080/00221689509498667

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A mathematical model and numerical simulation has been used to test the validity of a water and thermal circulation scheme induced by the implementation of a new power plant in the Zeebrugge harbour. The aim of the study was to: a) verify that in the interior basin of the inner harbour, a sufficient stratification is present to allow for the capture of cold bottom waters, whereas the ejected heated water remains at the surface and is evacuated to the main harbour, b) study the way the water cools in the main harbour and to quantify the amount of thermal energy which is pumped back into the inner harbour, c) determine if the global heat excess is evacuated and if the resulting temperature increase remains within reasonable limits at the power plant pump inlet. The study, accomplished in three steps, determined the parameters that control the recirculation (e.g. atmospheric conditions) and what their relative importance is. It was shown that a stratification is created in the interior basin. In the main harbour the heat evacuation is done primarily by evaporation in the harbour and only for 20% by the outflow to the open sea.

ISSN:0022-1686    

DOI:10.1080/00221689509498668

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Entrainment characteristics across a density stratified interface inside a two-dimensional flume compartment were investigated experimentally. The interface was formed by a generally quiescent body of fresh water floating on top of sea water. Relative motion between the two stratified layers was induced by a uni-directional flow below the compartment. This in turn set up flow circulations within the seawater layer. In the tests, the compartment length, the mean velocity of the sea water flow, and the height of the density interface above the compartment bottom were varied in order to evaluate their influence on the entrainment rates. The effects of slotted barriers across the compartment bottom on the entrainment rates were also examined. The entrainment coefficient can be expressed in terms of dimensionless parameters related to significant flow and geometrical parameters. By means of regression analyses of the test data, an empirical equation for the entrainment rate was established.

ISSN:0022-1686    

DOI:10.1080/00221689509498669

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

This paper presents a critical study of hydraulic jumps, submerged jumps and plane turbulent wall jets as a class of similar flows. Using the experimental results available in the literature as well as some new results, the hydraulic jump and the wall jet are shown to be the end states with the submerged jumps forming the transition state in between. The three properties considered are the similarity of the velocity distribution, decay of the velocity scale and the growth of the length scale. The velocity distribution is approximately the same for all the flows. Using a longer length scale L, the decay of the velocity scales for the end states has been redefined and for submerged jumps, the decay has been found to be either free-jump-like (FJL) or wall-jet-like (WJL). The variation of the length scale L was found to have distinctive variations for the different flows. Some new results are also presented for the reverse flow field of submerged jumps.

ISSN:0022-1686    

DOI:10.1080/00221689509498670

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A numerical solution is presented for the standard step method of'calculating the free surface profile in gradually varied flow. Based on the Manning equation for friction slope, the solution employs the Newton-Raphson approximation. No simplifying assumptions are made concerning the cross-section geometry. The solution is applied to the particular cases of trapezoidal and rectangular channels with a constant bed slope.

ISSN:0022-1686    

DOI:10.1080/00221689509498671

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The paper presents a numerical model based upon the Reynolds equations with a one-equation turbulence closure. A finite element formulation with a weak form of the method of characteristics is applied.

ISSN:0022-1686    

DOI:10.1080/00221689509498672

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The objective of this paper is to show the results of simulations of the flow near spur dikes using a three dimensional numerical model. Special attention was given to the simulation of the wake formed downstream of the dyke and the influence of the eddy viscosity field on velocities, flow depths and reattachment lengths. The most important features of the model are described. Comparisons with flume measurements conducted at the Franzius Institute in Hannover, Germany are also presented.

ISSN:0022-1686    

DOI:10.1080/00221689509498673

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

This paper provides some results of field investigations of bed topography and local scour at groynes in two bends of the Warta River. Concave banks of these bends are protected by impermeable groynes oriented upstream with almost constant spacing and geometric shape. Both bed topography in bends and local scour holes at the groyne heads were formed by channel flows equal to or smaller than the mean annual discharge. A two-dimensional (horizontal) numerical model of water and (bed-load) sediment motion for steady-state conditions was used to calculate the general bend scour. A new equation for a maximum scour depth prediction at groynes located along an outer bank of a bend is introduced. The maximum scour depth occurs inside the groyne field. This local scour is a function of a depth and depth-average flow velocity along the concave bank, spacing and location relative to the bend, and orientation to flow.

ISSN:0022-1686    

DOI:10.1080/00221689509498674

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

UNDULAR BORES IN OPEN CHANNELS - EXPERIMENTAL STUDIESby A. Treske, Journal of Hydraulic Research, Vol. 32, 1994, No. 3, pp. 355-370

ISSN:0022-1686    

DOI:10.1080/00221689509498675

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

END DEPTH IN TRAPEZOIDAL AND EXPONENTIAL CHANNELSS. Murty Bhallamudi, Journal of Hydraulic Research, Vol. 32, 1994, No. 2, pp. 219-232

ISSN:0022-1686    

DOI:10.1080/00221689509498676

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor