ISSN:0022-1686    

DOI:10.1080/00221688909499239

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

An experimental investigation on regular wave induced forces on a smooth submarine pipeline fixed horizontally near a simulated seabed is carried out in the inertia dominated regime. A simple potential flow around the cylinder is assumed in analysing the hydrodynamic forces on submarine pipelines considering the size of the pipe' and wave conditions employed in this study. The inline hydrodynamic coefficient of inertia and transverse hydrodynamic coefficients of lift and vertical inertia are evaluated using the measured forces and through the use of least squares method. These inline and transverse hydrodynamic coefficients are correlated with the scattering parameter and gap ratio of the pipeline from the seabed. Further the effect of depth parameter on these hydrodynamic force coefficients is investigated.

ISSN:0022-1686    

DOI:10.1080/00221688909499240

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A directional wavemaker theory is presented for waves in wave basins with sloping bottoms and reflective sidewalls. The theory includes the refraction, shoaling and diffraction that occur in wave basins with the wavemaker mounted along one end of the basin. A procedure is shown which utilizes the reflection from the sidewalls to produce planar wave trains at a given location in the basin, similar to that which would be obtained by an infinitely long wavemaker.

ISSN:0022-1686    

DOI:10.1080/00221688909499241

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Flow of a plunging density current in a diverging horizontal channel is analyzed using a two layer nonmiscible flow model. The equations governing the flow are presented. Interface profiles that can exist are identified, and the behavior of the flow densimetric Froude number at the plunge line is investigated. The theoretical results are compared with experimental data.

ISSN:0022-1686    

DOI:10.1080/00221688909499242

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The method of characteristics is used to calculate numerical solutions for water waves generated in a reservoir by a relatively close landslide. The landslide is modelled with a vertical wall that moves a horizontal distance of at least ten reservoir depths into the reservoir and follows an assumed velocity variation with time. This allows the generated wave to be approximated with nonlinear, non-dispersive long-wave approximations. The final results are shown with dimensionless plots of maximum wave heights as functions of time and distance for both one-dimensional and axisymmetric solutions.

ISSN:0022-1686    

DOI:10.1080/00221688909499243

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Experiments in an open channel were conducted to investigate the formation of ripples on an erodible sand bed by varying the roughness, the mass density of the uniform grain material and the history of the bed evolution. A first set ofexperiments was conducted by gradually increasing the slope in small increments from a value at which no transport occurred to one at which ripples started forming. In a supplementary set. the same slope change was achieved rapidly in a single step. Visualizations showed that two types of ripple formation exist, depending on how fast the slope rate was increased. A third type is observed for fine and heavy bed material (lead) at high bed load transport. The results can be interpreted by using a coherent structure model for the turbulent flow. In the framework of such a concept, the initial disturbances can be interpreted as transport relics of so-called sweep events, and the initial wave length is related to the sweep “periods”.

ISSN:0022-1686    

DOI:10.1080/00221688909499244

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Experiments in a flume with a compound section are described, in which lateral shear stress profiles were measured for various flow depths and inclinations of the main channel bank. General forms of bed shear stress profiles on the flood plain are described and the dependence of the turbulent interaction between channel and flood plain flows on flow depth and on the inclination of the main channel bank is examined. A dimensionless parameter is proposed for representing the intensity of turbulent interaction and is used as the independent variable to develop a model for predicting the shear stress profile on the bed of a flood plain. Equations are presented for predicting the value of this independent variable.

ISSN:0022-1686    

DOI:10.1080/00221688909499245

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The Darcy-Weisbach formula, used in the majority of mathematic models for calculating the head losses in the unsteady motion of water does not simulate with sufficient accuracy the damping of flow and pressure in the water hammer phenomenon. Taking into account the dynamic structure of water column motion in a pressurized pipe, for a compressible fluid, as well as the energy losses in the elastic walls of the pipe, we present for the calculation of the flow and pressure oscillation damping a formula based on the structural (hysteretic) friction forces [6, 13]. In the case of elastic bodies the structural damping forces are proportional to the elastic forces, but a quarter of a period phase out. By putting into practice the presented formula a good agreement between computations and experimental measurements is achieved.

ISSN:0022-1686    

DOI:10.1080/00221688909499246

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Spatial lag effects, which are viewed as the inability of an alluvial system to immediately overcome the presence of constrained sediment boundary conditions, are investigated under bed load sediment transport conditions. An equation which characterises spatial lag effects and two theoretical spatial lag coefficient relations are investigated experimentally. Values of the spatial lag coefficient obtained from experimental data are compared with the theoretical relations and one relation is recommended. A numerical model which incorporates the spatial lag equation is formulated. The performance of the model is tested against data measured by a previous investigator and the ability of the model to successfully predict the spatial and temporal variation of the mean bed elevation and bed load transport rate under steady flow, non-equilibrium conditions is verified.

ISSN:0022-1686    

DOI:10.1080/00221688909499247

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Aim of this paper is to present a mathematical description of the flow profile in a river of which the discharge decreases gradually due to percolation. Subject to assumptions (uncurved, prismatic channel with fixed, flat bottom and constant slope, uniform velocity distribution) two ordinary differential equations can be derived, one describing the depth and the other the discharge, both as a function of the place. In determining the boundary conditions the singular points of these equations play an important part. In order to verify the theoretical approach, model experiments were carried out in a laboratory flume. The main conclusion is that the theoretical results are very sensitive to the accuracy with which the permeability of the bottom is determined.

ISSN:0022-1686    

DOI:10.1080/00221688909499248

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor