摘要:

Cavitation erosion damage to spillway surfaces may be prevented with the use of aeration devices (aerators) introducing air in the layers close to the channel bottom in order to reduce cavitation damage. The performance of a spillway aerator are studied on steep spillway model with high velocities (from 4 m/s up to 15 m/s) and new air concentration and velocity measurements were performed. The data are presented and analysed developping new equations. The behaviour of the air demand relationship between the air discharge and the subpressure in the cavity beneath the nappe is analyzed. All these results provide a better understanding of the air entrainment processes above a spillway aerator and the quantity of air entrained can be obtained.

ISSN:0022-1686    

DOI:10.1080/00221688909499166

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Beam and Warming implicit Unite difference schemes are introduced to integrate the equations describing the two-dimensional unsteady free-surface flows. These schemes are second-order accurate in space and time, allow sharp discontinuous initial conditions, and do not require isolation of a bore. Subcritical and supercritical flows may be present indifferent parts of the channel or they may occur in sequence. Depending upon the Courant number used in the computations, sharp discontinuities may be slightly smeared since they are not isolated. Different procedures for incorporating the boundary conditions are discussed. The analysis of two-dimensional unsteady free-surface (lows resulting from the breaking of a dam are presented to illustrate the aplication of the methods.

ISSN:0022-1686    

DOI:10.1080/00221688909499167

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Friction velocity vector probes have been designed for two-dimensional fluid flow based on a flush-mounted hot film operated in constant temperature mode. The magnitude of, was obtained with steady-state calibration curves in the reversing (separating) flow tested. The direction is determined from the result of an anti-coincidence correlation program with forward-backward discrimination of the thermal wake. Probe performance is evaluated for flow in an open channel with a submerged block atRe= 11,000 by measuring time-averaged vector values(x) in the longitudinal centerline. The reattachment position was found atx/h= 7.0. From the energy gradient of the channel flow and integration of the friction velocities along the transect theCDvalue of the block with a length/height ratio of 3.57 is found to be 3.1.

ISSN:0022-1686    

DOI:10.1080/00221688909499168

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A perturbation approach is used to estimate the error involved in the level-reservoir approximation. Bed resistance is neglected, and zero inflow is assumed to occur at the moving shoreline. The results show that the level-reservoir approximation is valid when reservoir levels change relatively slowly. The approximation is also used to obtain a boundary condition in tidal calculations for shorelines with sloping boundaries, and a simple example is worked.

ISSN:0022-1686    

DOI:10.1080/00221688909499169

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

An empirical equation has been developed for rate of bed-load transport based on shear stresses, bed friction coefficient and particle properties. It has been calibrated by using laboratory and field data covering a limited range of sediment sizes (from fine non-cohesive silt up to a median size of 1.4 mm) and has been shown to apply to streams transporting sediment of median size up to 300 mm. Development of this equation followed the lead given by Bagnold (1980, 1986) and extended his work so that it can be applied to unsteady flows. It is in a form suitable for use in the study of estuaries and coasts. The parameters in the equation can be obtained in the field without great difficulty.

ISSN:0022-1686    

DOI:10.1080/00221688909499170

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A planar plunging jel can drive penetrating, attached, wavy or tranquil flows depending on its plunge angle and the geometry of the receiving chamber. Geometries considered here include supported and free-fall weir flows into a rectangular receiving chamber, and idealised siphon-priming model configurations. The very different air entrainment, detrainment and net transport characteristics of these patterns have practical importance for the design of aeration and downshaft hydraulic equipment as well as the priming of large siphon units. Two main studies are reported here, the first concerned with classification and characterisation of some main features of the flow patterns, the second with predictive calculations of bubble transport and detrainment in penetrating flows - the pattern of most practical concern for many applications.

ISSN:0022-1686    

DOI:10.1080/00221688909499171

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The case of a hydraulic jump in a closed conduit with pressure flow downstream from the jump has been investigated for horizontal conduits by a number of researchers. In the research reported herein, the influence of conduit slope is considered, including very steep slopes (up to 30%). The theoretical analysis of this case does not lead to a direct solution for jump height because there are too many unknowns in the equation. Accordingly, experimental observations were made for a wide range of Froude numbers and slopes, and non-dimensional design curves are provided.

ISSN:0022-1686    

DOI:10.1080/00221688909499172

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A detailed analysis of energy conversions in a fully developed channel flow on a sloping plane is provided. It is the lowering of the centre of mass that releases potential energy which, of course, ultimately will leave the domain as a boundary heat flux.

ISSN:0022-1686    

DOI:10.1080/00221688909499173

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A theoretical analysis of the liquid free-surface formation and the development of fine silt concentration caused by the influence of a prevailing combined vortex is presented. Similarity relationships for both parameters have been found to exist. Burgers' vortex has been used to derive approximate formulae for the free-surface and the concentration profiles. Finally, using the present analysis, values for the diffusion coefficient have been calculated.

ISSN:0022-1686    

DOI:10.1080/00221688909499174

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The internal flow features of hydraulic jumps in trapezoidal channels are explored. Based on 3-D observations, it is shown that the flow phenomena significantly differ from the classical hydraulic jump. This is particularly attributed to the presence of a bottom roller.

ISSN:0022-1686    

DOI:10.1080/00221688909499175

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor