The critical temperature gradient model of Rebut, Lallia and Watkins is compared with data from Alcator C. The predicted central electron temperature is derived from the model, and a simple analytic formula is given. It is found to be in quite good agreement with the observed temperatures on Alcator C under ohmic heating conditions. However, the thermal diffusivity postulated in the model for g...

Coordination of water movement among plant organs is important for understanding plant water use strategies. The hydraulic segmentation hypothesis (HSH) proposes that hydraulic conductance in shorter lived, 'expendable' organs such as leaves and longer lived, more 'expensive' organs such as stems may be decoupled, with resistance in leaves acting as a bottleneck or 'safety valve'. We tested the...

A large-scale, natural-gradient tracer test in a heterogeneous aquifer at a site near Columbus, Miss. is simulated using three-dimensional (3D) hydraulic conductivity distributions derived from the borehole flowmeter test data. The simulated plume is more sensitive to the way the hydraulic conductivity field is interpolated from the measured data than it is to the dispersivity value. The transp...

Sediment erosion not only reduces efficiency and life of hydropower turbines but also causes problems in operation and maintenance. Several factors are responsible for this erosion in hydro turbine components. This paper presents the sediment erosion types in hydraulic turbines and their components based upon an extensive literature review and the field observation at Cahua hydropower plant, Pe...

This research describes the goals, design and implementation of a quasi natural gradient, laboratory scale, sand tank (aquifer) model experiment. The model was used to study the transport of an inorganic tracer (Chloride) in groundwater, within a tropical aquifer (porous medium) material. Three-dimensional sand tank (1.8 m × 0.3 m × 0.8 m) experiments were conducted to investigate contaminant t...

The performance of an explicit algebraic stress model is assessed in predicting the turbulent ow and forced heat transfer in straight ducts, with square, rectangular, trapezoidal and triangular cross sections, under fully developed conditions over a range of Reynolds numbers. Iso-thermal conditions are imposed on the duct walls, and the turbulent heat uxes are modeled by gradient-di usion type ...

A variational formulation has been developed to solve a parabolic partial differential equation describing free-surface flows in a porous medium. The variational finite element method is used to obtain a discrete form of equations for a two-dimensional domain. The matrix characteristics and the stability criteria have been investigated to develop a stable numerical algorithm for solving the gov...

Sustainable, environmentally friendly and resource-saving water and nutrient management in horticulture requires knowledge of the hydraulic suitability of horticultural substrates for each specific application. The aim of this study was to develop methods and a rating framework to assess the hydraulic performance of horticultural substrates. The hydraulic criteria related to high-quality hortic...