Damage Assessment of Concrete under Wind-Sand Load

In this paper, a numerical model of wind-sand flow is established to explore the influence of wind-sand flow parameters on the stress state of the concrete. According to the contact mechanics theory, the wind erosion critical pressure of concrete members and the corresponding stress state of concrete are analyzed. A wind erosion damage assessment index based on stress fatigue theory is proposed.

Research of the resistance process of casing column filters at their contact with rock

The analysis of theoretical solutions and experimental data given in numerous literatures to justify the choice of the ratio of the size of gravel in relation to the size of formation sand showed that with the development of experimental methods and the accumulation of laboratory and field data, this ratio tends to decrease. When installing filters in an open hole, pressure losses at the interface between gravel and the formation play a significant role, and it should be noted that the greatest productivity and efficiency of the filter in an open hole is achieved when there is a packing around it, which can be created by crushing the sandy massif of the formation by cyclical changes debit. When choosing a filter design, along with the ability to provide them with a reliable hydraulic connection in the reservoir-filter system, the main task is also solved - to prevent sand flow into the well. The study of the conditions for the removal of sand particles through the flow sections in perforated, mesh and slotted filters during their operation both in homogeneous and in sands of different size, made it possible to recommend empirical dependences for determining the size of the holes. Keywords: porous medium; coarse fraction; sand; particle; well.

Multiphase Flow in Circular and Triangular Pipes: Examining Flow Characteristics, Sand Erosion and Heat Transfer Via CFD and Experimental Work

Air-water two-phase flow in circular pipes has been studied by many investigators. However, investigations of multiphase flow in non-circular pipes are still very rare. Triangular pipes have found a number of applications, such as multiphase flow conditioning, erosion mitigation in elbows, compact heat exchanges, solar heat collectors, and electronic cooling systems. This work presents a survey of air-water and air-water-sand flow through circular and triangular pipes. The main objective of this investigation is to study the potential effects of triangular pipe geometry on flow patterns, slug frequency, sand erosion in elbows, and heat transfer in multiphase flow. Firstly, twenty-three experiments were performed for horizontal air-water flow. Detailed videos and slug frequency measurements were collected through circular and triangular clear pipes to identify flow patterns and create a database for these pipe configurations. The effect of corners of the triangular pipe on the liquid distribution was investigated using two different orientations of triangular pipe: apex upward and downward and results of triangular pipes were compared to round tubes. Secondly, ultrasonic wall thickness erosion measurements, paint removal studies, and CFD simulations were carried out to investigate the erosion patterns and magnitudes for liquid-sand and liquid-gas-sand flows in circular and triangular elbows with the same radius of curvature and cross-sectional area. Thirdly, heat transfer rates for liquid flows were also simulated for both circular and triangular pipe cross-sections. Although similar flow patterns are observed in circular and triangular pipe configurations, the orientation of the triangular pipes seems to have an effect on the liquid distribution and slug frequency. For higher liquid rates, slug frequencies are consistently lower in the triangular pipe as compared to the circular pipe. Similarly, the triangular elbow offers better flow behavior as compared to circular elbows when investigated numerically with similar flow rates for erosion patterns for both liquid-sand flow and liquid-gas-sand flows. Experimental and CFD results show that erosion in the circular elbow is about three times larger than in the triangular elbow. Paint studies results validated erosion patterns and their relations with particle impacts. Finally, heat transfer to/from triangular pipes is shown to be more efficient than in circular pipes, making them attractive for compact heat exchangers and heat collectors. This paper represents a novel experimental work and CFD simulations to examine the effects of pipe geometries on multiphase flow in pipes with several practical applications. The present results will help to determine the efficiency of utilizing triangular pipes as compared to circular pipes for several important applications and field operations such as reducing slug frequencies of multiphase flow in pipes, and reducing solid particle erosion of elbows, and also increasing the efficiency of heat exchangers.

Wind Tunnel Test on Windblown Sand Two-Phase Flow Characteristics in Arid Desert Regions

Windblown sand two-phase flow characteristics become an essential factor in evaluating the windblown sand load on infrastructures and civil structures. Based on the measured wind characteristics in arid desert regions, windblown sand flow fields with three kinds of sand beds are simulated in the wind tunnel, respectively. The results indicate that the characteristic saltation height of sand particles increases with the wind speed and particle size in the windblown sand flow field. As the sand concentration increases, the wind speed decreases, and the turbulence intensity increases. The concentration, energy, and impact pressure of sand particles increase with increasing wind speed and decrease exponentially with increasing height. At the same wind speed, the concentration, energy, and impact pressure of the coarse sand, fine sand, and mixed sand increases, in turn. Moreover, the variation of kinetic energy with height is similar to that of total energy with height and the proportion of potential energy to total energy is quite small.

Review of Research on Wind-sand Hazards in China Railway

China is the country with the longest mileage in the construction of sandstorms in the world. The railway system is often affected by wind sand flow, which seriously affects the operation safety of trains. Firstly, this article introduces the formation mechanism, movement state, monitoring method and structural characteristics of the wind-sand flow. Then the sand hazard formation mechanism of railway embankments, cuts, bridges and culverts is explained based on aerodynamic performance. Moreover, the sand prevention measures are classified, and the advantages and disadvantages of various measures are discussed. Finally, two kinds of sand prevention and control systems are proposed in combination with the topography and regional wind-sand flow characteristics, and the problems that need to be solved urgently in the prevention and treatment of railway sand and sand disasters in the future are prospected.