Search

Assuming time-averaged normalized velocity as a random variable, the present work developed a Renyi entropy-based model for deriving one-dimensional and two-dimensional velocity distributions in seepage-affected alluvial channels. The model requires the maximization of Renyi entropy using the principle of maximum entropy, subject to specified constraints. The derived velocity distributions can have maximum velocity on or below the free surface. The velocity distributions were evaluated with laboratory observations and were also compared with theoretical velocity distributions reported in the literature. The Renyi entropy-based 2D velocity distributions satisfactorily agreed with experimental data, and compared well with reported distributions. Also, the Renyi entropy provided more accurate 2D velocity distribution in the near-bed flow of seepage experiments than the other technique. The present paper concluded that the Renyi entropy model can be used to predict the velocity distribution in seepage flows. [ABSTRACT FROM AUTHOR]

A tractable analytical solution for steady-state two-dimensional seepage from a trapezoidal channel in a homogeneous, isotropic porous medium of considerable depth is presented. The analysis is performed by applying the method of inversion and the Schwarz-Christoffel transformation accounting for the capillary action. Because the right half-seepage domain is a mirror image of the left half-seepage domain about the vertical axis (on either side of the channel central plane) owing to the axisymmetric channel, a solution is sought for the right half-seepage domain. The results show that an increase in channel bottom width boosts seepage flux. On the other hand, an increase in channel side slope also amplifies seepage flux. In addition, capillarity plays a subtle role in augmenting the seepage flux from a channel. The analysis suggests that the dynamic capillary rise (i.e., the vertical rise of seepage water along the side slope owing to capillary action) is always less than the static capillary rise. The analysis also presents the relation for the seepage velocity distribution along a channel perimeter. The equations of seepage line coordinates yield the seepage line initially curving downward with a significant lateral shift and eventually becoming vertical at a great depth. Particular solutions for the triangular and rectangular channels and the vertical slit, which is a channel with vertical sides and negligible top width, can be obtained from the generalized solution for the trapezoidal channel. Therefore, this study provides insight into the hydraulics of seepage from a trapezoidal channel, including its particular cases, revealing some new features. [ABSTRACT FROM AUTHOR]

High groundwater flow velocity is a major challenge in many artificial ground freezing (AGF) projects, especially in groundwater control projects. That condition may be unfavorable for the formation of a frozen body. This study aims to understand the effect of seepage flow on the heat transfer behavior and hydraulic conductivity variation of sand during the freezing process in AGF projects by using a vertically buried freezing pipe. The authors conducted a small-scale laboratory experiment that combined a flow test, freezing process, and infrared thermograph observations of thermal distribution. The authors prepared saturated Toyoura sand and a Toyoura-silica sand layer combination as the heat-transfer medium. The thermal distribution and hydraulic conductivity behavior were investigated by two series of freezing experiments with different sand layers and flow scenarios. Infrared thermograph observation results showed how water affects the thermal distribution characteristic, whereas flow test results showed the relation between hydraulic conductivity and frozen-body development. [ABSTRACT FROM AUTHOR]

The authors introduce an experimental method that focuses on the flowthermal relation and the visual observation of heat distribution around a cooling pipe in sand under the flow condition. This experiment aims to understand the effect of seepage flow on the heat transfer behavior of sand under cooling and freezing conditions due to a vertically buried heat exchanger pipe. This method combines a flow test, cooling or freezing processes, and the visual observations of temperature profiles with saturated Toyoura sand as the heat transfer medium. Avertical copper pipe inserted into the sand medium is used as the thermal exchanger, while an infrared thermograph is used to measure and visualize the surface-temperature profile of the specimen. The heat transfer distribution behavior is investigated by conducting a series of cooling and freezing experiments on the specimens with variation of the flow rate condition, initial condition, and pipe depth. The thermograph observation results show how water flow obviously affects the shape and intensity of the heat distribution. [ABSTRACT FROM AUTHOR]

On a gabion stepped chute, the steps contribute to the dissipation of turbulent kinetic energy, free-surface aeration may be intense, and there are complex interactions between the free-surface flow and seepage motion. Detailed measurements were conducted in a relatively large gabion stepped spillway model. Using a combination of high-speed movies and phase-detection probe measurements, the air--water flow properties in the step cavities and in the gabions were documented. Strong air--water exchanges between seepage and stepped cavity flows were observed. The data showed a complex bubbly seepage motion in the gabions associated with a high level of interactions between seepage and free-surface flows, leading to a modification of the step cavity recirculation and lesser flow resistance. [ABSTRACT FROM AUTHOR]