摘要:

Laboratory experiments on mixed-layer deepening in a density-stratified fluid are known to be affected by side-wall friction, in particular when the overall Richardson number Ri*= B/u*2is large where B is the total mixed-layer buoyancy and u*the friction velocity. Finite aspect (depth to width)-ratio effects are calculated starting from a simple mathematical model based on the gradienttransport hypothesis. An asymptotic expansion for large Ri*, which covers almost the whole range of practical interest, yields good agreement with the entrainment rates observed by Kantha, Phillips and Azad (1977) and Deardorff and Willis (1982). At zero aspect-ratio the dimensionless entrainment rate E*= We/u*, where we is the entrainment rate, is found to vary as Ri*-1/2for both two-layer fluid and an initial density distribution according to a power law, which result is in agreement with the Pollard, Rhines and Thompson (1973) model. A similar analysis of the experiments of Moore and Long (1971) shows that most of these experiments were controlled by side-wall friction.

ISSN:0022-1686    

DOI:10.1080/00221688309499439

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Turbulent mixing flow in open (or closed) conduit sudden expansions (single or double step with no strong eddy interference) are analyzed. The flow is found to be self-preserving in character after an original normalization procedure transformed streamwise velocity profiles into single profiles invariant with streamwise distance. Hence, a simplified form of the Navier-Stokes equations to describe the expansion mixing flow, is transformed into an ordinary differential equation by similarity considerations. Analytical and numerical solutions to the reduced problem are sought, the former from a linearized form of the ordinary differential equation, and the latter from the complete third-order non-linear differential equation. The computed results are in good agreement with experimental data.

ISSN:0022-1686    

DOI:10.1080/00221688309499440

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The paper presents a mathematical model of vertical circulation in a density-stratified reservoir for the case of axially symmetric flow. An analytical solution of the present problem is given in terms of Fourier series. The solution comprehends two special cases, of gradually and continuously converging channels, for which a mechanism of formation of the surface circulation region is described. The method takes account of additional horizontal density changes in a reservoir. Those appear to have significant influence upon the extent of the region of circulation.

ISSN:0022-1686    

DOI:10.1080/00221688309499441

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Soil properties have profound effects on overland flows over porous media. These effects are investigated by using a surface-subsurface flow conjunctive simulation model which solves the Saint- Venant equations for the overland flow and Richards' equation for the two-dimensional unsaturated and saturated porous medium flow. Guided by a dimensional analysis, four soil properties are studied, namely, porosity, vertical and horizontal saturated hydraulic conductivities, and unsaturated soil hydraulic characteristics which is expressed in two pairs of parameters describing the relationships between the degree of saturation and suction pressure, and between the relative conductivity and suction pressure, respectively. The results confirm the common belief that overland flow increases for decreasing soil porosity or saturated conductivity while the infiltration into the soil decreases. The effect of the ratio between horizontal and vertical saturated conductivity is insignificant, indicating the soil anisotropic effect is unimportant. Moreover, the overland flow decreases and infiltration increases for soils having small suction pressure head in the saturation and relative conductivity vs. suction pressure relationships, corresponding to, e.g., increasing soil particle sizes, than for soils having large suction pressure head.

ISSN:0022-1686    

DOI:10.1080/00221688309499442

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

SEEPAGE AND GROUNDWATER (Developments in Water Sciences, 13)by: M.A. MARINO AND J.N. LUTHIN Elsevier Scientific Publishers, P.O. Box 211, 1000 AE Amsterdam, The Netherlands (1982). 489 pages, US$ U6.50/Dfl. 250,–, ISBN 0-444-41975-6.

ISSN:0022-1686    

DOI:10.1080/00221688309499443

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

ISSN:0022-1686    

DOI:10.1080/00221688309499438

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor