摘要:

The methods and advantages of the experimental approach to hydraulic problems are examined on the basis of three examples from environmental fluid mechanics: saltwater intrusion control in estuaries, gas transfer at the air-water interface and coherent structures in shallow water flows.

ISSN:0022-1686    

DOI:10.1080/00221689209498919

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A system analogous to a hydropower plant with a slender cylindrical body floating vertically in the surge shaft is studied. This is done in the context of a general study to see whether a throttled surge shaft can dampen oscillations.

ISSN:0022-1686    

DOI:10.1080/00221689209498920

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The governing equations for surge oscillations in a closed surge chamber yield a second-order nonlinear differential equation for constant power. The surge stability is investigated by the direct method of Liapunov, which introduces the Liapunov function from the energy consideration. The nonlinear terms arising from large surges are included. The resulting stability criterion is demonstrated on a phase plane. For the equilibrium point of practical interest, the stability diagram specifies domains of asymptotic stability as a function of the safety factor of the surge-chamber. The diagram indicates that large-amplitude surges necessitate larger chamber size than that laid down by Svee for damping and the surge stability deteriorates with downward oscillations. By postulating sinusoidal surge motion, the critical chamber area is equal to the product of the critical area in case of small oscillations (Svee's formula) and a factor greater than 1.0. The factor is a function of surge amplitude and air cushion parameters for given turbine head. Stability criteria for open surge tanks can be obtained as special cases of those for closed ones.

ISSN:0022-1686    

DOI:10.1080/00221689209498921

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Air entrainment in secondary (brook) intake shafts creates two types of problems in the waterways of hydro electric power plants; blowouts and supersaturation of dissolved air. Blowouts may damage structures and supersaturation may cause gas-bubble disease in fish. Several preventive measures have been suggested to avoid supersaturation. At Driva hydroelectric plant a so-called vacuum gate was chosen. The present article describes prototype measurement of air entrainment and formation of supersaturation both under atmospheric conditions and under reduced air pressure in the shaft.

ISSN:0022-1686    

DOI:10.1080/00221689209498922

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

An efficient mathematical model for calculation of the boundary shear stress field induced by raindrop impact is developed and tested using numerical and experimental data. The model comprises a series of dimensionally consistent, closed-form, algebraic equations, written in terms of physically meaningful parameters describing the fluid properties and initial conditions at the instant of drop impact. The relationships in the model are derived from the analysis of data generated by a computer code which numerically solves the Navier-Stokes equations for two-dimensional flow of a viscous, incompressible fluid with a free surface. The resulting simplified, algebraic model is validated using data from laboratory experiments which employ hot-film anemometry to measure drop induced boundary shear stresses. Substantial agreement is found between model and experimental results with regard to the boundary shear stress magnitudes and sensitivity of magnitudes to different water layer depths, drops sizes, drop velocities and distances from the center of drop impact.

ISSN:0022-1686    

DOI:10.1080/00221689209498923

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The results of a preliminary experimental investigation into the merging of buoyant discharges in an ambient current are presented. Trajectory and dilution data from the merging buoyant flows are reported. The investigation shows that the conditions at the point of merging have an important effect on the behaviour of such flows. It is also shown that if there is an ambient current there may be some advantage in designing an outfall such that the buoyant flows merge.

ISSN:0022-1686    

DOI:10.1080/00221689209498924

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

This paper presents the results of an experimental study on intersecting circular turbulent jets of equal momentum flux, with the angle of intersection increasing from 30 to 120 degrees. The resulting flow has been divided into region 1 from the nozzle to the intersection point (IP) and region 2 downstream of the IP. In both these regions, observations have been made on the axial velocity and pressure fields. Using these results and dimensional considerations, the main features of this flow configuration have been predicted.

ISSN:0022-1686    

DOI:10.1080/00221689209498925

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

This paper describes an experimental study of the drag force experienced by a stationary smooth sphere placed in a boundary layer type gradient flow. The test sphere was kept close to as well as away from the boundary. Both smooth and rough boundary conditions were studied. The Reynolds number varied in the range of 3.62 x 103to 6.45 x 104while the relative size defined as the ratio of sphere diameter to the nominal thickness of the boundary layer varied from 0.29 to 1.0. Notwithstanding its variation with the relative size, the drag coefficient-Reynolds number function in the present study is closer to that of a sphere falling freely through infinite fluid and appreciably below that for a sphere rolling allong smooth and rough boundaries.

ISSN:0022-1686    

DOI:10.1080/00221689209498926

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The depth-integrated model for suspended sediment transport based on the asymptotic solution of the convection-diffusion equation developed by Galappatti (Galappatti and Vreugdenhil, 1985) is generalized. The validity and applicability of the generalised model is studied by analysing the convergence of the asymptotic solution and the morphological behaviour of the model.

ISSN:0022-1686    

DOI:10.1080/00221689209498927

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

ISSN:0022-1686    

DOI:10.1080/00221689209498928

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor