Movement Of Sand Particles Research Articles

Analysis and Application of Particle Backtracking Algorithm in Wind–Sand Two-Phase Flow Using SPH Method

Due to the high sensitivity of grid-based micro-scale wind–sand flow models to deformation and distortion, this study employs the Smooth Particle Hydrodynamics (SPH) method for numerical simulations. The advantage of the SPH method is that it can dynamically analyze the entire trajectory of the particles, thus allowing the initial positional distribution of sand-buried particles to be traced. This study utilizes the advantages of the SPH method. It develops particle backtracking algorithms based on the SPH method using the C language. It analyses the initial location distribution, concentration, velocity, and particle size distribution of sand-buried particles to formulate targeted measures to cope with wind–sand disasters. Meanwhile, this paper improves a particle modeling algorithm to realize arbitrary mixing particle size and mixing ratio by programming in C language and combining it with pixel recognition technology. In addition, this paper will use the particle backtracking algorithm to analyze the classical embankment wind and sand flow field and then propose adequate measures for embankment wind and sand disaster management by investigating sand particle movement characteristics.

Modeling and Simulation of Sand Particle Trajectories and Erosion in a Transonic Fan Stage

Abstract In desert regions, the high concentrations of dust and sand particles carried by storms are sucked into aircraft engines, leading to severe erosion. This numerical study analyses the movement of sand particles and the erosion process in the front components of a high-bypass turbofan engine (HBTFE). The components include the Pitot intake, spinner, fan, core flow inlet guide vanes (IGVs), and secondary flow outlet guide vanes (OGVs). The study focuses on the engine operating conditions during takeoff from a Saharan airfield. The flow field data is obtained separately, and exported to an in-house particle tracking code based on the Lagrangian approach. The finite element method (FEM) is used to track the particles as they move through the mesh cells and determine the precise impacts and conditions to calculate the local erosion rates and material removal. Obtained results indicate large numbers of sand particles impacting the fan blade at high frequency from the hub up to approximately 80% of the span, due to their deflection by the Pitot intake lip and outer contour. The pressure side (PS) of the fan blade experiences extreme erosion rates, while the highest erosion rates occur at the leading edge (LE) and towards the trailing edge (TE). At the exit of the fan blade, a significant amount of particles pass through the OGVs and typically erode its PS, while fewer particles from the lower sections of the fan pass through the IGVs. These findings reveal the erosion-prone areas that need special coating protection.

Erosion and Deposition Patterns Over a Wind‐Blown Sand Dune Behind a High Vertical‐Type Sand Fence

ABSTRACTSand dunes are the primary factor influencing wind‐sand disasters. To explore the evolution law of wind‐blown sand dunes surrounding high vertical‐type sand fences along desert railways, numerical simulation analyses based on computational fluid dynamics coupled with a discreet element method of the wind‐sand flow field and sand particles trajectories around sand fences were conducted. The focus of this study was the Yandun section of the Lanzhou‐Xinjiang Railway in Xinjiang, China (42.38°N, 93.95°E). By combining ERA5 wind data with field measurements and monitoring, a three‐dimensional coupling model was established. According to the results of L9 (33) orthogonal tests, the sensitivity of the three factors to the evolution of sand dunes can be ordered as wind speed > porosity > height, indicating that wind speed is closely related to sand dune evolution (p < 0.05). The results of single‐factor tests indicate that the structure of wind‐sand flow fields, sand accumulation patterns, and sand particle movement trajectories vary significantly under different wind speeds. The sand accumulation rates on the windward slope of the sand dune are 29.67%, 25.91%, and 20.04%, while on the leeward slope, these rates are 40.33%, 34.09%, and 29.96%, respectively. The obtained information on the evolution law of sand dunes surrounding high vertical‐type sand fences provides a scientific basis for wind‐sand prevention measures along railways in desert regions.

Sand improvement by microbial-induced carbonate precipitation with casein micelles

This study explores the incorporation of casein micelles to improve the conventional microbial-induced carbonate precipitation technique used for soil improvement. With a single application of the proposed biocementing agent containing casein micelles, a mixed slurry of natural sand solidified to self-sustaining strength within 48 h at 37°C was obtained. The stress–strain curves of the biocemented specimens obtained from a consolidated drained triaxial compression test exhibited sharp peaks at less than 1% strain. Under effective confining pressures of 30, 50 and 100 kPa, the peak deviatoric stress registered 415, 479 and 536 kPa, respectively – representing 1·8–4·1 times the maximum strength of the original sand. Vaterite calcium carbonate crystals formed by the biocementing agent ensured bridging between sand particles, resulting in the improved cohesion. The cohesion-derived residual strength tended to increase at the critical state in biocemented sand under the lowest confining stress. The localised shear band formed by the crystals may control the movement of sand particles, resulting in a change in volumetric strain behaviour. The formation of casein micelles induced the nucleation and growth of spherical crystals, acting as a casein-mediated vaterite. This formation likely contributed to the improved cohesion of sand observed in this study.

Effectiveness of Three Turbulence Modeling Approaches in a Crosswind–Sedan–Dune Computational Fluid Dynamics Framework

The aerodynamic loads of a sedan experience significant fluctuations when passing by a sand dune at the roadside under crosswinds, which can easily cause yawing and overturning. Computational fluid dynamics (CFD) methods, based on different turbulence modeling approaches, yield different aerodynamic results for sedans. This study aims to investigate the effects of three prevailing turbulence modeling approaches (renormalization group (RNG) k-ε, large eddy simulation (LES), and improved delayed detached eddy simulation (IDDES)) on the aerodynamic characteristics of a sedan passing by a sand dune under crosswinds. The CFD dynamic mesh models are constructed using the “mosaic” mesh technique to account for the dune–air–sedan interaction. The reliability of the CFD prediction method is verified by comparing it with field test results. The predictive capabilities of the three turbulence modeling approaches are compared in terms of aerodynamic loads and flow field characteristics. The simulation of sand particle movement is conducted through the discrete phase model, aiming to assess the impact of wind–sand flow on the aerodynamic properties of sedans. Corresponding results show that the aerodynamic loads predicted by the LES model closely match (within 4.4–7.5%) the corresponding data obtained from field tests. While the IDDES and LES models demonstrate similar abilities in characterizing the wind field details, and their results exhibit maximum differences of 8.3–15.7%. Meanwhile, the maximum difference between the results obtained by the RNG k-ε and LES models ranges from 14.8% to 18.4%, attributed to its inability to capture subtle changes in the vortex structure within the flow field. This work will provide a numerical modeling reference for studies on the wind–sand flow and the aerodynamic characteristics of sedans running through the desert, and it has implications for the safe driving of sedans under extreme conditions.

Study of turbulence intermittency in unstable atmospheric surface layer and its effect on saltation sand motion based on wavelet transform

Turbulence in the atmospheric surface layer, especially in deserts and semi-arid regions, significantly affects sand movement. In unstable stratification, turbulence exhibits complex intermittency, complicating its impact on saltation. This study uses wavelet transform analysis to examine the effects of turbulence intermittency in unstable stratification on saltation. Our analysis reveals that in unstable stratification, the energy distribution of turbulence is more dispersed, the intermittent characteristics are more significant, and the intermittent burst duration of streamwise turbulence is longer, while the vertical intermittent burst duration is shorter. The fitting formulas of the energy ratio and stratification stability of the streamwise wind speed, vertical wind speed, and temperature at different frequencies are given. In addition, there is a complex nonlinear relationship between stratification stability and friction velocity on saltation. In unstable stratification, the critical wind speed required for saltation is higher than that of near-neutral, and the jumping speed and horizontal transport are weakened. Moreover, the coherence between wind speed and saltation flux increases significantly at low frequency with the increase in instability, indicating that large-scale motion plays a key role in saltation under these conditions. The more unstable the stratification is, the more obvious the phase difference fluctuation of the low frequency part is, and the more unfavorable the formation of stable saltation sand conditions. This study reveals the turbulence intermittently and its complex effects on sand particle movement in unstable stratification, which is of great significance for predicting and controlling dust storms, land desertification, and soil erosion.

Measurement of sand particle motion speed in multiphase wind-sand flow based on piezoelectric ceramic sensors

Abstract Utilizing Pb(ZrTi)O3-5A piezoelectric ceramic (hereafter referred to as PZT-5A) as sensors, we studied the movement speed of sand particles in multiphase wind-sand flows. We developed a mathematical model that effectively links the impact force of sand grains with the output voltage of PZT-5A, incorporating factors such as the piezoelectric coefficient and sand particle characteristics. Additionally, we proposed a new method to accurately determine the elastic recovery coefficient of sand particles using PZT-5A sensor measurements and experimental setups, which is significant for the field of material science. Wind tunnel experiments revealed that at heights ranging from 0.1 to 1.0m, sand particle speeds range from 52.8% to 91.4% of wind speeds. As wind speed increases to 15m/s, sand particle speed nears 91.4% of wind speed. Yet, at a constant wind speed, sand speed drops as sediment discharge rises. This research offers fresh insights into sand particle dynamics in wind-sand contexts.

Research on optimizing the drilling rate for through-tubing drilling and sand pumping tools

The efficient, cost-effective removal of sand in low-pressure and prone-to-leakage oil and gas wells poses a significant challenge that is currently being researched. The limited size of the newly developed through-tubing drilling and sand pumping tool leads to sand plugging when the drilling rate is too fast and low sand cleaning efficiency when the drilling rate is too slow. To address this issue, this paper utilizes FLUENT to simulate the migration behavior of sand-laden fluid within the drilling and sand extraction tool. The DDPM discrete phase model is employed to examine the trajectory and motion of sand particles within the fluid. Through theoretical calculations, it is determined that when the average particle size of the sand solution is 0.05 mm and the inner diameter of the tubing is 50.3 mm, the drilling rate should be kept below 687 mm/min to prevent sand plugging. The validity of the theoretical analysis is confirmed through the construction of a testing platform. This study offers practical guidance for the implementation of the new through-tubing drilling and sand pumping tool in engineering applications. To provide a new solution for addressing the problem of low pressure and easily leaking oil and gas wells.

Local Similarity Between Aeolian Barchan Dunes and Their Downsized Subaqueous Counterparts

AbstractAeolian barchan dunes on Earth and other planets have been widely investigated. Much of the understanding of barchan dune morphodynamics comes from field observations, numerical simulations, and downsized water‐tunnel experiments as well. Many of the evolution of barchan dunes in water‐tunnel experiments are similar to those of aeolian cases, although they have notable differences in scale, sand particle motion and hydrodynamic characteristics. Here, we first review the literature on the local similarities between aeolian and downsized subaqueous barchan dunes, focusing on (a) dune formation, (b) dune morphology, (c) particle‐scale characteristics, and (d) sand/dune emission at horns. A comprehensive description of double‐dune interaction modes is then presented to illustrate the local similarity of barchan dune morphodynamics. Specifically, as the interaction mode undergoes a process of “merging‐splitting‐chasing,” the similarity between the interaction modes of aeolian and downsized subaqueous dunes continuously decreases. Furthermore, we summarize the significance and limitations of downsized water‐tunnel experiments for barchan dunes, and highlight the focus for future investigation.

Attempts to apply fiber optic sensing technology to desert research: laboratory measurement and field observation on the movement of desert sand particles.

Sand particle movement can lead to sand collision, which may even generate large amounts of sand dust and finally trigger a sandstorm. However, there is a lack of effective observation methods for sand particle scale at present due to the harsh environment of the desert. In this article, we attempt to use fiber optic sensing technology to address the above issues. Based on that, laboratory measurement and field observation of sand particle motion are carried out. In the laboratory, the sand particle vibration is detected. In the field observation, the results we obtained are consistent with the actual movement of sand particles. The proposed technique exhibits high resolution and good repeatability for sand particle motion measurement and observation. This work will promote the application of optical fiber sensing technology as a new means for desert research.

Transient phase in shear zone formation in sands

An experimental study has been made to study the emergence of narrow shear zones (“shear bands”), in uniformly graded quartzitic sand under dry conditions using the model setup of orthogonal cutting. A fixed region of interest around the stationary tool is imaged using a high-resolution and high-speed camera and further analyzed using Particle Image Velocimetry (PIV) algorithm to obtain the flow (velocity) fields. The velocity field maps of the near tool tip region demonstrate sharp change in the motion of sand particles along with the formation of a “dead zone” – a region of material stagnation or no flow. This extent of the dead zone was found to fluctuate in time for a given cutting speed, and no significant effect of the cutting speed (or strain rate) is observed in the propagation of dead zone size. The dynamic repose angle of the evolving sand pile in front of the tool increases initially and then attains a steady value of around 40°. The regions of intense straining in the sands were revealed in the effective strain rate fields. The shear localization was seen to emerge from the tooltip and propagate toward the free surface. The inclination angle of these bands evolves periodically with time and showed a decreasing trend due to an increase in the surcharge. The oscillatory force signatures suggested that every undisturbed ensemble of sands, on reaching the tool vicinity, undergoes material softening (dilation) followed by hardening(compaction), which is also reflected in the periodic formation and destruction of shear bands.

The Study of Structural Optimization on Hydraulic Performance and Anti-Clogging Performance of Labyrinth Drip Irrigation Emitters

The core component of a properly functioning drip irrigation system is the drip irrigation emitter. Irrigation water containing impurities and sand particles can easily lead to clogging of the drip irrigation emitter, reducing the efficiency of the drip irrigation system. In this paper, orthogonal tests were used to optimize the flow channel structure, combined with the computational fluid dynamics–discrete element method (CFD-DEM) to analyze the flow index and sand particle motion characteristics. Clear water tests and short-cycle anticlogging tests were used to validate the results of the numerical simulation, and the relationship between the hydraulic performance and anti-clogging performance was revealed via linear regression. The results showed that the structural parameters of drip irrigation emitters were important factors affecting the flow index and sand movement characteristics. The order from largest to smallest was the turning angle, amount of interdental reference, flow channel depth, flow channel width, and width of the top base. The sand passage rate and the percentage decrease in velocity can be used as important indicators of anti-clogging performance, and there was a negative correlation between the two indicators. The flow channel with a 65° turning angle had the lowest flow index, and the sand passage rate can reach up to 91.48%; the reason was that the main flow region velocity was higher, the vortex region and the sand energy loss were small, which was not easy to clog. The equation for the relationship between flow index and sand passage rate was a negative correlation for drip irrigation emitters between a 65° and 75° turning angle. The drip irrigation emitter with a 65° turning angle had better hydraulic performance and anti-clogging performance.

The influences of boundary layer thickness on the characteristics of saltation sand flow – A large eddy simulation study

In this paper, Large Eddy Simulation (LES) of turbulence and Lagrangian model of sand particle motion are adopted to study the characteristics of wind-blown sand flow for different boundary layer thickness. The simulations are conducted within computational domain height (boundary layer thickness) of δ = 0.5 m, 1 m, 5 m and 12 m, respectively. It is found by comparing the computational results that the mass flux and sand transport rate increase with the increase of boundary layer thickness for the same frictional wind velocity, and the fluctuation of particle velocity and sand transport rate increase significantly too. The spatial scales of particle structure, defined by the correlation of sand particle concentration, significantly increase with δ, so does the time scale of statistical stability of sand transport rate. For two computational domains of δ = 1 m and 12 m, the statistical relative error of sand transport rate reduce to less than 5 % only when the average time goes higher than 45 δ/Ub, where Ub is the bulk fluid velocity. In the context of turbulence, it might take about 10 mins to obtain reliable sand statistics in the neutral atmospheric boundary layer whose boundary layer thickness is about 100–200 m.

Sedimentation motion of sand particles in moving water (I): The resistance on a small sphere moving in non-uniform flow

In hydraulics, when we deal with the problem of sand particles moving relative to the surrounding water, Stokes’ formula of resistance has usually been used to render the velocity of sedimentation of the particles. But such an approach has not been proved rigorously, and its accuracy must be carefully considered. In this paper, we discuss the problem of a sphere moving in a non-uniform flow field, on the basis of the fundamental theory of hydrodynamics. We introduce two assumptions: i) the diameter of the sphere is much smaller than the linear dimension of the flow field, and ii) the velocity of the sphere relative to the surrounding water is very small. Using these two assumptions, we solve the linearized Navier-Stokes equations and equations of continuity by the method of Laplace transform, and finally we obtain a formula for the resistance acting on a sphere moving in a non-uniform flow field.

Effects of Covering Layer of Sand Particles on Particle‐Bed Collision and Aeolian Sand Transport

AbstractThe movement of sand particles on the desert is the primary mechanism resulting in the development of sandstorms. Scientists have found that the physicochemical environments of terrestrial planets can cause the surface of sand particles to form a peelable covering layer, which may shed gradually during the movement of sand particles and affect the collision process between sand particles and bed surface, and finally affect aeolian sand transport itself. However, only a few studies have investigated these microscopic physical processes and conducted quantitative analysis of the relationship between covering layer mass and its coefficient of restitution (COR) when a particle impact desert surface. In this study, we collected four types of natural sand particles from the Badain Jaran, Mu Us, and Taklimakan deserts and the shoreside of the Yellow River respectively. A hydrochloric acid solution was used to dissolve the surface‐covering layer of sand particles, and high‐speed photography was used to capture the process of particle‐bed collision. The motion characteristics of the sand particles under different covering layers were analyzed using statistical analysis, and the quantitative formula between the COR and the covering layer mass was provided. This calculation result was further incorporated into an aeolian sand transport model to evaluate the effect of the covering layer on sand flux. Considering the ubiquity of covering layer on sand particle, the methodology proposed in this study can be used to simulate sand drift on Earth, Mars, and other terrestrial planets more accurately.

Estimation of Bed Shear Stress in Shallow Transitional Flows under Condition of Incipient Motion of Sand Particles Using Turbulence Characteristics

In this experimental study, using an ADV, experiments were performed in three different shallow water flows under hydraulically transitional flow condition to estimate the bed shear stress using turbulence characteristics. Vertical distributions of all shear and normal Reynolds stresses as well as TKE were evaluated and simplified in order to estimate bed shear stress under incipient motion of four groups of sand particles. To determine bed shear stress, as the main approach, the linear portion of the −u′w′ profiles were extended towards the channel bed. The necessity of the approach of the vector addition of −u′w′ and −v′w′ in this experimental study was examined. It was found that the bed shear stress can be effectively estimated by multiplying the values of u′20, v′20, w′20 and TKE0 by 0.17, 0.33, 1.24 and 0.2, respectively. However, it was found that these values were slightly proportional to the shear Reynolds number. Additionally, the one-point measurement approach was assessed. The TKE method which applies all three components of Reynolds normal stresses was preferred to the u′2, v′2 and w′2 methods. Results showed that, u′20, v′20 and w′20 have values of 60.5, 31.3 and 8.2 percent of the total, respectively.

Influence of Fiber Type and Length on Mechanical Properties of MICP-Treated Sand.

Fibers are applied in construction work to improve the strength and avoid brittle failure of soil. In this paper, we analyze the impact mechanism of fiber type and length on the immobilization of microorganisms from macroscopic and microscopic perspectives with fibers of 0.2% volume fraction added to microbial-induced calcite precipitation (MICP)-treated sand. Results show the following: (1) The unconfined compressive strength (UCS) of MICP-treated sand first increases and then decreases with increasing fiber length because short fiber reinforcement can promote the precipitation of calcium carbonate, and the network formed between the fibers limits the movement of sand particles and enhances the strength of the microbial solidified sand. However, the agglomeration caused by overlong fibers leads to uneven distribution of calcium carbonate and a reduction in strength. The optimal fiber length of polypropylene, glass, and polyvinyl alcohol fiber is 9 mm, and that of basalt fiber is 12 mm. (2) The UCS of the different fiber types, from small to large, is basalt fiber < polypropylene fiber < glass fiber < polyvinyl alcohol fiber because the quality of the fiber monofilament differs. More fibers result in more a evident effect of interlacing and bending on sand and higher strength in consolidated sand.

Permeability Analysis of Hydrate-Bearing Porous Media Considering the Effect of Phase Transition and Mechanical Strain during the Shear Process

Summary The permeability characteristics of hydrate-bearing reservoirs are critical factors governing gas and water flow during gas hydrate exploitation. Herein, X-ray microcomputed tomography (CT) and the pore network model (PNM) are applied to study the dynamic gas and water relative permeabilities (krg and krw) of hydrate-bearing porous media during the shear process. As such, the dynamic region extraction method of hydrate-bearing porous media under continuous shear is adopted by considering deformation in the vertical direction. The results show that krw and krg of hydrate-bearing porous media are influenced by the effect of disordered sand particle movement under axial strain. Declines in the critical pore structure factors (pore space connectivity, pore size, and throat size) contribute to the reduction in krw and the increase in krg. However, krg decreases during the shear process at a high water saturation (Sw) because of the high threshold pressure and flow channel blockage. In addition, the connate water saturation (Swc) continuously increases during the shear process. Swc is influenced by pore size, throat size, and flow channel blockage. Moreover, the preferential flow direction of krg and krw changes during the continuous shear process. The results of dynamic permeability evolution during the continuous shear process under triaxial stress provide a reference for pore-scale gas and water flow regulation analysis.

Characteristics of the Wind Distribution Using Automatic Weather System Observation Data over the Doyo-deung Barrier Islands off the Coast of the Nakdong River Estuary, Busan, South Korea

Lee, J.-H.; Woo, H.J.; Jung, H.-S.; Park, H.N.; Jeong, E.-Y., and Jeong, J.B., 2021. Characteristics of the wind distribution using automatic weather system observation data over the Doyo-deung barrier islands off the coast of the Nakdong River estuary, Busan, South Korea. In: Lee, J.L.; Suh, K.-S.; Lee, B.; Shin, S., and Lee, J. (eds.), Crisis and Integrated Management for Coastal and Marine Safety. Journal of Coastal Research, Special Issue No. 114, pp. 36–40. Coconut Creek (Florida), ISSN 0749-0208. This study was conducted to the Nakdong marine environmental information system (N-MEIS) using automatic weather station (AWS) observation data to elucidate the characteristics of the wind distribution, focusing on and land and sea breezes, over the Doyo-deung barrier islands in the brackish water zone off the coast of the Nakdong River Estuary, Busan, South Korea. From May 2015 to the present, the N-MEIS was run in real-time using 4th Generation (4G) long term evolution (LTE) communication, with a coverage rate of approximately 98% from AWS, along with periodic marine observations recorded one to four times per year. From April 2016 to August 2020, the average monthly wind speed over the Doyo-deung barrier islands was 3.82 m/s (range, 2.10–5.10 m/s) and the maximum wind speed, recorded in February 2019, was 46.80 m/s. These values are generally influenced by low-pressure cyclones or gusty winds. However, the maximum monthly mean velocity may be influenced by typhoons occurring in early autumn, from August to September. Based on the percentage of each wind direction, the prevailing winds are from the N, NNE, SSW, and NNW. The distribution of wind directions in summer was similar to that in spring, while that in autumn tended to be similar to that in winter. However, considering only wind speeds of 5.00 m/s or more, which can cause the movement of sand particles, N, SSW, and NNW winds are overwhelmingly dominant, at 38.7%. Research into the dynamic wind distribution is essential to effectively managing erosion and sedimentation around barrier islands, beach pollution from floating materials transported overland, coastal sand dune activity, changes in migratory bird habitats, and impacts on ecosystem health. The evolution and development of the N-MEIS will facilitate this process. Future studies should integrate real-time data with periodic marine observations and predictions and environmental sensitivity index maps.

Evaluation of Incipient Motion of Sand Particles by Different Indirect Methods in Erosion Function Apparatus

An experiment was carried out in an acrylic glass-sided re-circulating closed conduit with a rectangular cross section, which is similar in construction to an erosion function apparatus. An adjustable sand box, made of acrylic glass, was attached to the bottom of the conduit as the sand zone or the test section. The hydraulics of the flow in the erosion function apparatus is complicated due to the limited part of the non-smooth and erodible soil surface attached to the closed conduit. As the bed shear stress changes with the bed roughness, even though the flow velocity does not change, establishing a method to estimate the incipient motion is an important challenge for an erosion function apparatus. The present study was conducted to explore the incipient motion of sands from bed shear stress estimated by four different indirect methods on both the sand bed and the smooth bed installed in the erosion function apparatus. In the experiment, particle image velocimetry (PIV) was used to investigate flow dynamics and incipient motion in terms of dimensionless critical bed shear stress. The experimental results show that the bed shear stress estimated from the log-law profiles in the sand zone and the smooth zones are relatively higher than those of the other indirect methods. The dimensionless critical bed shear stress of threshold condition evaluated by all indirect methods was found in good agreement with those of previous results in both zones. The Manning roughness and Darcy–Weisbach friction coefficients were evaluated based on the critical shear velocity at the incipient motion. Although these coefficients were found slightly greater in the smooth zone than in the sand zone, in both zones, they showed good agreement with previous studies.