Numerical Analysis of Rainfall Infiltration in the Slope with a Fracture

With the finite volume method, a 2D numerical model for seepage in unsaturated soil has been established to study the rainfall infiltration in the fractured slope.The result shows that more rain may infiltrate into the slope due to existing fracture and then the pore pressure rises correspondingly. Very probably, it is one of the crucial factors accounting for slope failure. Furthermore a preliminary study has been conducted to investigate the influence of various fracture and rainfall factors such as the depth, width and location of a crack, surface condition, rainfall intensity and duration. Pore pressure and water volumetric content during the transient seepage are carefully examined to reveal the intrinsic mechanism.

Numerical Study on Rainfall Infiltration in Rock-Soil Blocks

A mathematical model for the rain infiltration in the rock-soil slop has been established and solved by using the finite element method. The unsteady water infiltrating process has been simulated to get water content both in the homogeneous and heterogeneous media. The simulated results show that the rock blocks in the rock-soil slop can cause the wetting front moving fast. If the rain intensity is increased, the saturated region will be formed quickly while other conditions are the same. If the rain intensity keeps a constant, it is possible to accelerate the generation of the saturated region by properly increasing the vertical filtration rate of the rock-soil slop. However, if the vertical filtration rate is so far greater than the rain intensity, it will be difficult to form the saturated region in the rock-soil slop. The numerical method was verified by comparing the calculation results with the field test data.

Steady Patterns of Microparticles Formed by Optical Tweezers

In this paper, we propose a method for forming steady patterns of microparticles in a dispersion using optical tweezers. We demonstrate how to control the congregation of particles in a dispersion and to manually fabricate a pattern, The steady pattern (nay be useful for in-depth research, and the method will have applications in biology and nanotechnology.

Study on Flow Patterns of Oscillatory Thermocapillary Convection In Floating Half Zone by PIV

The velocity fields of oscillatory convection have been measured using the techniques of Particle Image Velocimetry (PIV) in a liquid bridge of half floating zone with small typical scales of a few millimeters for emphasizing the thermocapillary effect in comparison with the effect of buoyancy. The flow patterns of the oscillatory flow have been studied experimentally in a liquid bridge. The flow patterns in the liquid bridge are classified with mode numbers according to oscillatory flow characteristics. Results of the experiment show that the mode depends on the aspect ratio as well as the volume ratio of the liquid bridge. The experimental results are helpful for studying the structure of flow at the onset of oscillatory thermocapillary convection in a liquid bridge.

Experimental study on two-phase gas-liquid flow patterns at normal and reduced gravity conditions

Experimental studies have been performed for horizontal two-phase air-water flows at normal and reduced gravity conditions in a square cross-section channel. The experiments at reduced gravity are conducted on board the Russian IL-76 reduced gravity airplane. Four flow patterns, namely bubble, slug, slug-annular transition and annular flows, are observed depending on the liquid and gas superficial velocities at both conditions. Semi-theoretical Weber number model is developed to include the shape influence on the slug-annular transition. It is shown that its prediction is in reasonable agreement with the experimental slug-annular transition under both conditions. For the case of two-phase gas-liquid flow with large value of the Froude number, the drift-flux model can predict well the observed boundary between bubble and slug flows.

Microgravity experiments of two-phase flow patterns aboard Mir Space Station

A first experimental study on two-phase how patterns at a long-term, steady microgravity condition was conducted on board the Russian Space Station "MIR" in August 1999. Carbogal and air are used as the liquid and the gas phase, respectively. Bubble, slug, slug-annular transitional, and annular hows are observed. A new region of annular how with lower liquid superficial velocity is discovered, and the region of the slug-annular transitional flow is wider than that observed by experiments on board the parabolic aircraft. The main patterns are bubble, slug-annular transitional and annular flows based on the experiments on board MIR space station. Some influences on the two-phase how patterns in the present experiments are discussed.

Modeling on Runoff Concentration Caused by Rainfall on Hillslopes and Application in Maoping Slope

Based on the fact that the concentration flowlines of overland flow depend on the surface landform of hillslope, a kinematic wave model was developed for simulating runoff generation and flow concentration caused by rainfall on hillslopes. The model-simulated results agree well with experimental observations. Applying the model to the practical case of Maoping slope, we obtained the characteristics of runoff generation and infiltration on the slope. Especially, the simulated results adequately reflected the confluent pattern of surface runoff, which offers a scientific foundation for designing the drainage engineering on the Maoping slope.

Two-phase flow patterns in a 90 degrees bend at microgravity

Bends are widely used in pipelines carrying single- and two-phase fluids in both ground and space applications. In particular, they play more important role in space applications due to the extreme spatial constraints. In the present study, a set of experimental data of two-phase flow patterns and their transitions in a 90degrees bend with inner diameter of 12.7 mm. and curvature radius of 76.5 mm at microgravity conditions are reported. Gas and liquid superficial velocities are found to range from (1.0 similar to 23.6) m/s for gas and (0.09 similar to 0.5) m/s for liquid, respectively. Three major flow patterns, namely slug, slug-annular transitional, and annular flows, are observed in this study. Focusing on the differences between flow patterns in bends and their counterparts in straight pipes, detailed analyses of their characteristics are made. The transitions between adjoining flow patterns are found to be more or less the same as those in straight pipes, and can be predicted using Weber number models satisfactorily. The reasons for such agreement are carefully examined.

Numerical study on rainfall infiltration in rock-soil slop

A mathematical model for the rain infiltration in the rock-soil slop has been established and solved by using the finite element method. The unsteady water infiltrating process has been simulated to get water content both in the homogeneous and heterogeneous media. The simulated results show that the rock blocks in the rock-soil slop can cause the wetting front moving fast. If the rain intensity is increased, the saturated region will be formed quickly while other conditions are the same. If the rain intensity keeps a constant, it is possible to accelerate the generation of the saturated region by properly increasing the vertical filtration rate of the rock-soil slop. However, if the vertical filtration rate is so far greater than the rain intensity, it will be difficult to form the saturated region in the rock-soil slop. The numerical method was verified by comparing the calculation results with the field test data.

Wavelike patterns in one-dimensional coupled map lattices

We investigate the existence of wavelike solution for the logistic coupled map lattices for which the spatiotemporal periodic patterns can be predicted by a simple two-dimensional mapping. The existence of such wavelike solutions is proved by the implicit function theorem with constraints. We also examine the stabilities of these wave solutions under perturbations of uniform small deformation type. We show that in some specific cases these perturbations are completely general. The technique used in this paper is also applicable to investigate other space-time regular patterns.

Measurements of Flow Patterns and Velocities of Gas -Water Two -Phase Flows Using Electrical Resistance Imaging

This paper presents a measurement of flow patterns and flow velocities of gas-water two-phase flows based on the technique of electrical resistance tomography (ERT) in a 40m horizontal flow loop. A single-plane and dual-plane ERT sensor on conductive ring technique were used to gather sufficient information for the implementation of flow characteristics particularly flow pattern recognition and air cavity velocity measurement. A fast data collection strategy was applied to the dual-plane ERT sensor and an iterative algorithm was used for image reconstruction. Results, in respect to flow patterns and velocity maps, are reported.

Effects of rainfall infiltration on the stability of soil slopes

Slope failure due to rainfall is a common geotechnical problem. The mechanics of rainfall induced landslides involves the interaction of a number of complex hydrologic and geotechnical factors. This study attempts to identify the influence of some of these factors on the stability of soil slope including rainfall intensity, hydraulic conductivity and the strength parameters of soil.

Effects of rainfall infiltration on deep slope failure

With the finite element method and the limit equilibrium method, a numerical model has been estab-lished for examining the effects of rainfall infiltration on the stability of slopes. This model is able to reflect the variations in pore water pressure field in slopes, dead weight of the soil, and soil softening caused by rainfall infiltration. As a case study, an actual landslide located at the Nongji Jixiao in Chongqing was studied to analyze the effects of rainfall infiltration on the seepage field and slope sta-bility. The simulated results showed that a deep slope failure is prone to occur when rainfall infiltration leads to a remarkable variation in the seepage field, especially when the pore water pressure in slopes increases in a large range.

Conical Emission Patterns by Femtosecond Pulses with Different Spectral Bandwidths

Different conical emission (CE) patterns are obtained experimentally at various incident powers and beam sizes of pump laser pulses with pulse durations of 7 fs, 44 fs and 100 fs. The results show that it is the incident power but not the incident power density that determines a certain CE pattern. In addition, the critical powers for similar CE patterns are nearly the same for the laser pulses with the same spectral bandwidth. Furthermore, as far as a certain CE pattern is concerned, the wider the spectral bandwidth of pump laser pulse is, the higher the critical power is. This will hopefully provide new insights for the generation of CE pattern in optical medium.