ISSN:0022-1686    

DOI:10.1080/00221689309498825

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

ISSN:0022-1686    

DOI:10.1080/00221689309498826

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Lake Banyoles is a multibasin lake dominated by groundwater derived inflows. It is composed of three major basins, two of them being meromictic. The relatively warm and saline groundwater inflows, together with the basin morphometry, give rise to characteristic thermal structures in each basin, with different thermocline levels and temperature inversions distinguishing the basins. A one-dimensional lake mixing model has been adapted to include the form of mixing associated with the groundwater inflows, and the results are compared with data collected from the lake.

ISSN:0022-1686    

DOI:10.1080/00221689309498827

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Diurnal stratification and its effects on wind-induced current and water qualities in a shallow eutrophicated lake are discussed based on the field data obtained in Lake Kasumigaura (36° N, 140° E, Japan). Diurnal stratification makes a weak thermocline with the temperature difference of about 1°C. Because a thermocline prevents the vertical momentum transport, it inevitably creates the two-layered flow pattern. The temperature profile has double-thermocline when the thermocline formed one day remains in the following morning. Then, the old thermocline tends to stay near the bottom for several days because the wind mixing works only on the new thermocline developed at upper elevation. DO concentration near the bottom markedly decreases under such condition, because the vertical DO transport is suppressed by the thermocline. P04–P is released at high rate from the bed sediments after DO concentration falls below 4 ppm. The entrainment rate is discussed with reference to the basic models which are the turbulent erosion model (TEM) and the dynamic instability model (DIM). It is concluded that DIM, rather than TEM, is suitable to explain the mixing of diurnal stratification observed in this study. The entrainment rateE[Um] is found to vary asRi[U*]-1, whereE[Um]=We/Um,Wzis the entrainment velocity, Um is the vertically averaged velocity in the mixed layer,Ri[U*] =B/U*2,Bis the buoyancy of the mixed layer andU*is the friction velocity at the water surface.

ISSN:0022-1686    

DOI:10.1080/00221689309498828

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

An integrated programme of fieldwork and modelling was set up to improve model predictions of contaminant dispersion in rivers. The practical work investigated the turbulent structure of the River Severn in order to define parameters for the particle-tracking (random-walk) model. The model was then used to simulate dispersion on two reaches of the River Severn, and this paper describes the modelling work carried out. The results show promising agreement with measured concentrations of dye at several sections on the river.

ISSN:0022-1686    

DOI:10.1080/00221689309498829

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

An exploratory study is done to modelling of rivers on volcano slopes. Beside the occurrence of mud flows or lahars these rivers are characterised by unsteady supercritical flow and large suspended-sediment concentrations. A fully coupled 1D model is presented for the rivers, provided that lahars do not occur. It can simulate unsteady supercritical flow (Froude numbers between about 1 and 1.8) with volumetric sediment concentrations less than about 10%. The redistribution of the suspended-sediment concentration (i.e., the lag between concentration and transport capacity due to sediment relaxation) causes instabilities of the bed conformable to antidunes. Calculations with a numerical model using Preissmann's implicit scheme, and applied to a river on the Kelud Volcano in Indonesia, show the rapidity of bed-level variations and the upstream propagation and growth of bed disturbances. These results offer a deeper understanding in the problems of the rivers on the Kelud. Furthermore it yields a base for investigating the efficacy of sabo works.

ISSN:0022-1686    

DOI:10.1080/00221689309498830

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

By combined measurements of'incipient cavitation and water quality, characterized by its tensile strength, the enormous influence of differences in water quality on cavitation data is demonstrated. After eliminating these water quality effects from the test results general similarity relations for velocity and size scale effects become clearly apparent. The knowledge of the effects of water quality and the application of these relations can help to predict cavitation performance more precisely.

ISSN:0022-1686    

DOI:10.1080/00221689309498831

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

High velocity turbulent jets are often used in hydraulic structures to dissipate energy and to induce or enhance airentrainment. Examples include ski jumps and bottom aeration devices. This article presents new air concentration and velocity measurements performed in the flow development region of high velocity water jets. The measurements were obtained using a two-tips conductivity probe. The data are compared with analytical air concentration profiles derived from the diffusion equation, and theoretical velocity profiles of turbulent shear layers. The results highlight that the lower jet interface defined as C = 90% coincides with the streamline of maximum velocity gradient.

ISSN:0022-1686    

DOI:10.1080/00221689309498832

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A report is given of the results obtained from an experimental investigation into the effects of introducing a side overflow channel on the outer side of a channel bend. Entry to the overflow channel was controlled by a broad crested side weir. Comparisons are made of water surface profiles, depth-averaged velocities and deviation angles of the horizontal resultant velocities between bend only and bend with active overflow conditions. It was found that under conditions of low overflow rates, i.e. medium to high weir crest levels, the flow characteristics were virtually the same as for the bend only situation. However with low to medium weir crest levels, significant changes occurred upstream of, along and downstream of the weir section. In particular, a separation zone formed at the upstream end of the weir and a stagnation zone on the inner side of the channel bend.

ISSN:0022-1686    

DOI:10.1080/00221689309498833

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The unsteady bore wave diffraction patterns generated by a bore impinging on a circular cylinder and that generated by a bore passing through a contraction-expansion channel are simulated using high resolution nonoscillatory schemes. The two-dimensional shallow water equations in general curvilinear coordinates are used and the Strang-type dimensional splitting is employed. It was demonstrated that truly nonstationary hydraulic wave diffraction involving regular to Mach reflection, bore-bore collisions and their resulting complex interactions can be accurately computed by the present method.

ISSN:0022-1686    

DOI:10.1080/00221689309498834

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor