摘要:

This paper describes the results of a laboratory study of air entrainment below drops for a range of Drop numbers from 0.0007 to 0.0046. Characteristics of the plunging flow that occurs when the tailwaler depthytis in the range ofyt*. to h were studied whereyt*. is the value ofytwhen a hydraulic jump is formed at the section where Ihe deflected stream below the drop becomes parallel to the bed and h is the height of the drop. Air entrainment below the drop was studied for the jump withyt=yt*as well as for the plunging flows and approximate expressions have been developed for their air entrainment rates. These results can contribute to the estimation of the reaeration of polluted streams below drops.

ISSN:0022-1686    

DOI:10.1080/00221689609498458

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A hydraulic shear stress model for a uniform, steady flow on a slope of a mixture of water and a granular material al high concentration is presented here. The model includes stresses generated by particle-particle interactions along with those generated by fluid-bed interaction. Some results from the kinetic theory for granular flow are introduced to modify Bagnold's model for dispersive stresses. The model was verified experimentally by means of an inclined channel where silica-sand, supplied by a hopper, mixes with a uniform, steady water flow. Channel slopes range from 19 to 23 degrees. An interesting finding was obtained in the experiments presented here: there is not a continuous increase in velocity with depth of flow as stated by Manning's formula for the whole range of concentrations. The hydraulic model is able to reproduce the shape of the velocity vs. How depth curve and gives some insight about the mechanical behavior of the flow.

ISSN:0022-1686    

DOI:10.1080/00221689609498459

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A theoretical prediction for computing the sequent depth ratio of the hydraulic jump formed in rectangular sloping and roughened stilling basins is developed. It is based on the application of the one-dimensional momentum and continuity equations. The derived equation contains two nondimensional experimental coefficients, one for the effect of slope and the other one for the effect of' bed roughness. When the two coefficients are used together, the combined effect of both slope and roughness on the sequent depth ratio of the hydraulic jump can be computed. Experimental data verify the developed equation reasonably well.

ISSN:0022-1686    

DOI:10.1080/00221689609498460

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A fully conservative Beam and Warming scheme that uses Roe's approximate Jacobian is presented for solving transient open channel flows. A general treatment for satisfying entropy inequality condition is incorporated which always leads to a physically realistic solution. Details of the Beam and Warming scheme, inclusion of the source terms and proposed modifications for achieving full conservation are presented. Improvement in accuracy achieved with the proposed treatment is demonstrated by comparing numerical results by different versions of the scheme with analytical solutions. The applicability of the scheme is examined by comparing numerical results with experimental data and numerical results from existing studies. The scheme's response (o the Courant number and Manning's coefficient is also investigated.

ISSN:0022-1686    

DOI:10.1080/00221689609498461

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

In this study, a computer program is developed which enables us to design a water distribution system which satisfies all constraints including pipe diameters, low velocities, and nodal pressures with a minimum total cost. The hydraulic analysis of the water distribution system is performed by the Newton-Raphson method. This analysis is coupled with a non-linear optimization technique in order to minimize the design total cost. Accuracy of the developed computer program is approved by applying it to branched water distribution systems for which the optimum design can be calculated analytically in a simple manner. Comparison of the results indicates that the accuracy of the method used in this study is quite satisfactory.

ISSN:0022-1686    

DOI:10.1080/00221689609498462

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The analysis of hydraulic transients in pipes is traditionally carried out numerically. An approximate analytical solution of the nonlinear problem of unsteady flow in pipes is presented herein. The continuity and momentum equations are combined to give a nonlinear second-order hyperbolic partial differential equation whose approximate solution is derived using a perturbation technique called the delta expansion. It is shown that the zeroth-order perturbation solution gives ample accuracy for practical application. Useful series expansions for small values of the waterhammer parameter k are also obtained which compare extremely well with the results of the method of characteristics especially at small times. The explicit and simple form of the solution is suitable for further mathematical analysis and manipulation such as determining the maximal values and their time of occurrence. They are especially useful in determining the minimum time of closure possible while keeping the transient pressure in the pipe system within a specified limit.

ISSN:0022-1686    

DOI:10.1080/00221689609498463

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A two-dimensional numerical model which employs the depth-averaged forms of continuity and momentum equations along with k-c turbulence closure scheme is used to simulate the flow at the open channel divisions. The model is generalised to flows of arbitrary geometries and MacCormack finite volume method is used for solving governing equations. Application of cartesian version of the model to analyse the flow at right-angled junction is presented. The numerical predictions are compared with experimental data of earlier investigators and measurements made as part of the present study. Performance of the model in predicting discharge distribution, surface profiles, separation zone parameters and energy losses is evaluated and discussed in detail. To illustrate the application of the numerical model to analyse the flow in acute angled offtakes and streamlined branch entries, a few computational results are presented.

ISSN:0022-1686    

DOI:10.1080/00221689609498464

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A multi-layer water-sediment predictive model has been developed to study the effects of coastline reconfigurations on the three-dimensional (3-D) flow and sediment fields in coastal waters. The model is gridded with finite elements in the horizontal domain for easy adaptation to complex boundary configurations. The non-uniformity of flow and sediment distributions in the water column are represented by multiple vertically averaged layers. The Lax-Wendroff two-step scheme is used for time marching. This allows the flow field and sediment field to be explicitly coupled so that the density of the water-sediment mixture and the flow depth are updated without matrix inversion for the advanced time level. Because of the adoption of the explicit time-marching scheme, the allowed time increment of the present numerical scheme is relatively small. However, this is beneficial to studying short life activities such as sediment entrainment and deposition. The model predicted results were tested against field measurements in two case studies and good agreement was found in each case.

ISSN:0022-1686    

DOI:10.1080/00221689609498465

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Geometric and kinematic behavior of three-dimensional (3-D) negatively buoyant gravity plume spreading on a steep sloping surface has been investigated in a laboratory lank. Simple analytical expressions are presented based on the balance of driving and resisting forces, i.e., gravity, buoyancy, inertia, and friction, in both the longitudinal and lateral flow directions. These analytical expressions for spreading depend on the bottom slope, the initial buoyancy flux, the Richardson number, and the geometry of the plume at the source. Similar relations for a two-dimensional (2-D) gravity plume are also presented for comparison. Mathematical solutions show satisfactory agreement with measured experimental data.

ISSN:0022-1686    

DOI:10.1080/00221689609498466

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

AThis article presents a series of experiments with turbidity currents using two different types of sediments. During these experiments, the distributions of the velocity and of the concentration were measured simultaneously at three stations. The results show that the nondimensional velocity distribution is relatively insensitive to large variations in the concentration distribution. The article proposes some characteristic ratios, which allow a rough estimation of the flow structure in the body of a turbidity current, based on average physical quantities which can be measured in practice.

ISSN:0022-1686    

DOI:10.1080/00221689609498467

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor