Innovation in GIS Research UK     

Dr. Christine E. Dunn 《Transactions in GIS》2010,14(3):219-221

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DARCY'S COEFFICIENT OF PERMEABILITY AS SYMMETRIC TENSOR OF SECOND RANK     

A. C. LIAKOPOULOS Dr. Eng. 《水文科学杂志》2013,58(3):41-48

Synopsis

The dynamic equation of motion that governs the laminar flow of water through soils is the empirical equation of Darcy. According to Darcy's equation the velocity of the flowing water is proportional to the hydraulic gradient under which the water is flowing, with the constant of proportionality being the coefficient of permeability. The interesting question arising is whether or not the coefficient of permeability is a scalar quantity (having only a magnitude) or a vector (having both magnitude and direction). It is proved, in the present paper, that the permeability coefficient is neither a scalar nor a vector but a symmetric tensor of second rank. The fact that the permeability tensor is symmetric gives rise to great simplifications and permits a simple graphical construction of the tensor ellipsoid. Having the tensor ellipsoid, the determination of the direction at which the water will flow under a known imposed hydraulic gradient can be found graphically. In case of isotropic soils (the permeability coefficient has the same value along any direction) the ellipsoid reduces to a sphere and the tensor becomes a scalar. In the general case of anisotropic soils the permeability tensor is an entity with nine elements, six of which are independent representing pure extension or contraction along the three principal coordinate axes, thus transforming the permeability sphere into an ellipsoid and vice versa. It should be noted that in anisotropic soils the only directions along which the flow takes place in the direction of the hydraulic gradient are those of the principal axes of the tensor ellipsoid.

Permeability tests were conducted on anisotropic sandstone samples taken at different directions with respect to rectangular coordinates. The permeability coefficient values plotted on a two-dimensional polar coordinate graph paper give rise to an ellipse substantiating therefore the tensor concept of the permeability coefficient. The graphical construction of the tensor ellipse and the use of it in order to obtain the direction of flow by knowing the direction of the hydraulic gradient is also shown.  相似文献   

METEOROLOGICAL DATA REQUIRED IN THE HYDROLOGICAL SERVICE     

Dr. Eng. Julian LAMBOR 《水文科学杂志》2013,58(2):44-47

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A Review of the Symposium on Advanced Techniques in River Basin Management: the Trent Model Research Programme     

Dr. R. B. Painter 《水文科学杂志》2013,58(4):400-401

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TOWARDS WATER DEMAND MANAGEMENT     

Dr K. Szesztay 《水文科学杂志》2013,58(4):491-496

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Australia's great comet hunter     

Dr  Ragbir Bhathal 《Astronomy& Geophysics》2010,51(1):1.23-1.25

John Tebbutt was Australia's pre-eminent 19th-century astronomer who discovered two great comets of that century. Ragbir Bathal tells his story.  相似文献   

Ein Modell zur Bestimmung des Einflusses der klimatischen Bedingungen auf den Wärmehaushalt und das thermische Befinden des Menschen     

Doz. Dr. Karl Höschele 《Theoretical and Applied Climatology》1970,18(1):83-99

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SUJETS A TRAITER POUR L'ASSEMBLÉE DE 1960     

Dr.-Ing. Dieter LAUTERBACH  Eberhard GLOS 《水文科学杂志》2013,58(3):9-12

ABSTRACT

The present paper reports on some practical experiences gained in computing unit hydrographs (UH) according to the “classical” linear theory. The sizes of the drainage basins varied from 50 to 800 km² of hilly country.  相似文献   

SUR LES PROJECTS FUTURS DE L'AISH / ON THE FUTURE PLANS OF IAHS     

Dr. G. KOVACS 《水文科学杂志》2013,58(4):359-369

Abstract

The baseflow characteristics of some of the numerous small basins in southeastern Nigeria have been analysed to estimate the developable groundwater in the basins. It is shown that from 5.62 × 10⁴ to 1.59 × 10⁶ m³ of groundwater can be developed per square kilometre of basin per annum. The relationship between the baseflow characteristics and other attributes of the basins, such as geology and stream density, were studied statistically, leading to the development of empirical equations for predicting the hydrological features of the several ungauged streams in the region. It is shown, for example, that the basin geology (represented as the percentage of sands), the drainage density, the basin area, the baseflow depletion rate and the total groundwater stored in the basin, Q_tp, are related by the equation:

Q_tp = ?1.85 × 10⁹?7.96 × 10⁸ dd+4.18 × 10⁷ gf?2.01 × 10⁶ df+6.25 × 10⁵ wa

where dd is drainage density; gf geological factor; df depletion factor; and wa basin area.  相似文献   

ON TASKS AND INVESTIGATIONS IN MOUNTAIN REPRESENTATIVE BASINS     

Dr. T. S. ABALJAN 《水文科学杂志》2013,58(4):52-56

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