摘要:

Turbulence measurements were made in water and in a polyethylene oxide aqueous solution, using hot-film anemometry. Mean velocities, turbulence intensities, energy spectra and energy-dissipation rates were measured in a turbulent smooth-pipe flow. Mean flow structure showed that the mean velocity follows Virk's interactive-layer profile, and that the wall shear velocity is the proper velocity scale for polymer flows. Using Lumley's concept of an effective viscosity, the polymer spectra were cast into universal form and compared with Newtonian spectra. Results coincide reasonably well with the universal equilibrium theory. The major effect of the polymer additive appears to be an increase of the dissipative scales of the turbulence without significantly altering the basic structure of the flow, except near the wall.

ISSN:0022-1686    

DOI:10.1080/00221687609499675

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

Characteristics of free surface flow over a bed consisting of hemispherical roughness elements have been studied experimentally. Theoretical bottom of the channel has been located at a distance of 35% of the diameter below the tops of hemispheres. Usual logarithmic laws are valid for velocity distribution and friction factor as long as flow depth is large relative to roughness height. Equivalent sand roughness of the bottom is equal to 2.5 times the diameter of hemispheres. At large values of relative roughness, on the other hand, lower velocities are observed than the logarithmic law predicts, and friction factor also increases by as much as 50%. Intensity of turbulence fluctuations decreases with the increase of relative roughness. Probability density function of velocity fluctuations near the rough bed tends away from the normal distribution.

ISSN:0022-1686    

DOI:10.1080/00221687609499676

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

Results are presented of a series of experiments in which were measured: the mean critical bed shear stress at SHIELDS' grain-movement condition and at the initiation of non-ceasing scour, the rate of bedload transport, the average particle velocity, the rate of deposition, and the average length of individual steps of saltating bed-load particles, in water, as a function of the time-mean bed shear stress. These experiments were performed in a closed rectangular flow channel at different slopes of the bed surface and using five different bed materials (two sands, gravel, magnetite and walnut grains). Comparing the threshold drag acting at different downward slopes of the bed surface (0°, 12°, 18° and 22°) a surprisingly large critical-drag angle of 47° was found. The initiation of non-ceasing scour of a loose granular bed was studied experimentally behind a consolidated bed of the same material as the loose bed. The corresponding instantaneous threshold drag was about three times larger than the threshold drag acting at SHIELDS' grain movement condition.

ISSN:0022-1686    

DOI:10.1080/00221687609499677

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

An experimental study of swirling circular wall jets, with the swirl number equal to 0.141 and 0.265, has shown that the axial velocity profiles in the center plane are similar and are well described by the curve of the simple plane wall jet. The axial velocity distribution in the transverse direction (parallel to the wall) is also similar (in the neighbourhood of the wall) and is well described by the Goertler-type solution for the circular jet. The velocity scale decreases inversely with the axial distance whereas the length scales grow linearly with the axial distance. The effect of swirl is to make the velocity scale decay faster and it also makes the jet spread more rapidly in the transverse direction. The swirl also reduces the centerline bed shear stress effectively. The distribution of the bed shear stress in the transverse direction has been found to be similar.

ISSN:0022-1686    

DOI:10.1080/00221687609499678

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

Results are presented of numerical and analytical solutions for the drag and lift forces exerted in laminar flow on a two-dimensionally rough bed by wave action. As far as is known there are no other results, either experimental or theoretical, for the lift forces under these conditions and only two measurements, both at very high Reynolds numbers, of the drag. The mean skin-friction coefficient is also calculated but the agreement with experimental results is poor. The reasons for this disagreement are discussed.

ISSN:0022-1686    

DOI:10.1080/00221687609499679

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

ISSN:0022-1686    

DOI:10.1080/00221687609499680

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

SEDIMENT TRANSPORT IN ALLUVIAL STREAMS J. BOGARDI, Akadémia Kiadó (Publ. House of the Hungarian Academy of Science) 826 pp., Budapest, 1974. Price US $ 50.—.

ISSN:0022-1686    

DOI:10.1080/00221687609499681

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

ISSN:0022-1686    

DOI:10.1080/00221687609499674

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor