Scale dependency of dynamic relative permeability- satuartion curves in relation with fluid viscosity and dynamic capillary pressure effect

Capillary pressure–saturation-relative permeability relationships (Pc–Sw–Kr) are functions of importance in modeling and simulations of the hydrodynamics of two-phase flow in porous media. These relationships are found to be affected by porous medium and fluid properties but the manner in which they are affected is a topic of intense discussion. For example, reported trends in fluid viscosity and boundary conditions effects have been found to be contrary to each other in different studies. In this work, we determine the dependency of dynamic Kr–Sw relationships (averaged data) on domain scale in addition to investigating the effects of fluid viscosity and boundary pressure using silicone oil (i.e. 200 and 1000 cSt) and water as the respective non-wetting and wetting fluids with a view to eliminating some of the uncertainties reported in the literature. Water relative permeability, Krw, was found to increase with increasing wetting phase saturation but decreases with the increase in viscosity ratio. On the other hand, the oil relative permeability, Krnw, was found to increase with the increasing non-wetting phase saturation in addition to the increase in viscosity ratio. Also, it was found that with the increasing boundary pressure Krw decreases while Krnw increases. The influence of scale on relative permeability was slightly indicated in the non-wetting phase with Krnw decreasing as domain size increases. Effect of measurement location on dynamic relative permeability was explored which is rarely found in the literature. Comparison was also made between Kr–Sw relationships obtained under static and dynamic condition. Finally, mobility ratio (m) and dynamic coefficient (s) were plotted as a function of water saturation (Sw), which showed that m decreases as s increases at a given saturation, or vice versa

Scale dependency of dynamic relative permeability curves in relation with fluid viscosity ratio and dynamic capillary pressure effect

Scale dependency of dynamic relative permeability curves in relation with fluid viscosity ratio and dynamic capillary pressure effec

Effects of cross-section on infiltration and seepage in permeable stormwater channels

Factors affecting the infiltration rate have been studied fairly well by many researches; however, the effects of the cross-section of a permeable stormwater channel on the surface water depth reduction due to infiltration and seepage have largely been neglected. In the present study, towards improving the efficiency of permeable channels, the effects of the three components of a trapezoidal section, namely, the water depth, side slope, and base width, on the infiltration and unsteady seepage rates were investigated. Laboratory studies using models of the channel with unsaturated soil were performed under ponding condition using various initial water levels, base widths, and side slopes for two soil textures, namely, sandy loam and loamy sand. The results showed that the rate of surface water depth reduction by infiltration and seepage increases with increasing water level irrespective of the base width and side slope. In addition, an increase of the side slope increases the infiltration rate, with the effect becoming more significant with increasing initial water level, while the effect of varying the base width is insignificant

SIMPLIFIED DESIGN METHOD OF A TRANSMISSION CANAL

ABSTRACT A transmission canal loses water through seepage and evaporation. For economy, it should be divided into sub-sections and the cross-section for each of the sub-sections must be designed separately. This adds cost of transition in between two sub-sections, but the transition cost is overcome by reduced cost of the cross-section. Optimal design parameters for transmission canal based on the Manning equation are not available yet. This paper presents design equations for the least cost transmission canal considering earthwork cost which may vary with depth of excavation, cost of lining, and cost of water lost as seepage and evaporation from irrigation canals of triangular, rectangular, and trapezoidal shapes. This optimization problem is some sort of a dynamic programming, which is complicated due to unknown number of subsections i.e. number of unknown constraints. The problem was expressed in dimensionless form and then solved numerically. The optimal design equations along with the tabulated section shape coefficients provide a convenient method for the optimal design of a transmission canal. These optimal design equations and coefficients have been obtained by analyzing a very large number of optimal sections resulted from application of optimization procedure in the wide application ranges of input variables. The analysis consists of conceiving an appropriate functional form and then minimizing errors between the optimal values and the computed values from the conceived function with coefficients. Using the proposed equations along with the tabulated section shape coefficients, the optimal number of subsections and corresponding cost of a transmission canal can be obtained in single step computations