Sand Velocity Research Articles

Experimental study and models of the settling of sand in heavy oil

In heavy crude oil, high viscosity exerts a large drag force on sand particles. In this paper, the influence of heavy oil viscosity on the natural settlement of sand is studied, and two models of settling velocity are established. These models have many practical applications such as calculating the time for sand to settle and designing separators and setting tanks. To visually observe and record the sand settlement process, transparent industrial white oil is used to simulate heavy oil in this study. The settling of individual particles of sand under the gravity force is experimentally studied, and drag coefficients are determined. Various models are used to predict drag coefficients of spherical and nonspherical particles, and predicted values are compared with experimental values. The results are analyzed to explore the influence of sand particle morphology on the prediction of drag coefficients. Two dimensionless settling velocity models are established and used to analyze the behavior of sand particles in heavy oil; the results prove the reliability and applicability of the settling velocity model. In this study, a nonspherical particle drag coefficient model has no advantage over a spherical particle drag coefficient model in terms of prediction accuracy. Thus, it is not necessary to consider the influence of sand particle morphology when making predictions of the characteristic parameters of sand sedimentation in heavy oil. An explicit settling velocity model is established on the basis of the Brown-Lawler drag coefficient model, and its prediction accuracy is greater than 90% for the settlement velocity of sand in heavy oil.

A comparative study on equilibrium scour volume around circular cylinders in clay–sand mixed cohesive beds, at near threshold velocity of sand – an experimental approach

Abstract Local scour around a bridge pier is a complex phenomenon resulting from the interaction of the three-dimensional turbulent flow field around hydraulic structures. An accurate estimation of scour depth below the stream-bed is important during design since it determines the foundation levels and the expansion of the bridge foundation structures. The present study reveals the results of flume experiments on equilibrium scour depth and scour volumes around circular bridge pier models in clay–sand sediment mixtures. The scouring process in a cohesive sediment mixture is a complex interaction between clay–sand network structure and bed shear stresses. The bed shear stress reduces inside the scour hole as scour depth increases, and this is related to the different modes of scouring in clay–sand mixtures. An exponential equation for the non-dimensional scour volume is proposed considering all the experimental runs to get a specific understanding of the surrounding volume of scour hole from maximum equilibrium scour depth in a clay–sand mixed cohesive bed, when the approach flow velocity is near to the critical velocity for mixed sand. The proposed equations are validated using the pre-existing data from the literature dealing with experimental investigations on bridge scour using clay–sand mixed cohesive sediment and show good agreement with observed data.

Numerical Simulation on the Evolution of Tailings Pond Dam Failure Based on GDEM Method

Because of the continuous exploitation of metal minerals and the limited availability of land resources, many tailings ponds have been expanded. It is of great importance to dynamically calculate the critical parameters of flooding and sand velocity after a collapse, and quickly determine the dangerous area downstream on reducing the hidden dangers for an accident. In view of the limitations of the single finite element and discrete element methods for the simulation of tailings pond instability, the authors use the finite element and discrete element coupling method (GDEM) for the first time to carry out a dynamical process for numerical simulation of the evolution of a tailings pond collapse. The sediment movement and submerged range were compared with the results of the Volume of Fluid (VOF) method. The comparison shows that the change in drainage flow at the dam foundation position and the depth change in the downstream sensitive point after the dam break are consistent with the VOF calculation results, which indicates that the GDEM can be used as an effective means for the analysis of tailings dam failure. The calculation results of this method can provide technical support for the determination of dangerous areas downstream of tailings ponds and the safety management of key areas.

Protective Clothing Reduces Lower Limb Injury Severity Against Propelled Sand Debris in a Laboratory Setting

The contribution of energised environmental debris to injury patterns of the blast casualty is not known. The extent to which personal protective equipment (PPE) limits the injuries sustained by energised environmental debris following an explosive event is also not known. In this study, a cadaveric model exposed to a gas-gun mediated sand blast was utilised which reproduced soft-tissue injuries representative of those seen clinically following blast. Mean sand velocity across experiments was 506 ± 80 ms−1. Cadaveric samples wearing standard-issue PPE were shown to have a reduced injury severity to sand blast compared to control: a statistically significant reduction was seen in the total surface area (143 mm2vs. 658 mm2, p = 0.004) and depth of injuries (0 vs. 23 deep injuries, odds ratio = 0.0074, 95% confidence intervals 0.0004–0.1379). This study is the first to recreate wounds from propelled sand in a human cadaveric model. These findings implicate environmental debris, such as sand ejected from a blast event, as a critical mechanism of injury in the blast casualty. Tier 1 pelvic PPE was shown to reduce markedly the severity of injury. This injury mechanism should be a key focus of future research and mitigation strategies.

Research of amber extraction technology by vibroclassifier

The article presents basic information about the method of hydromechanical extraction of amber from amber-containing rocks, water-sludge scheme and classification scheme. The constructive scheme of the vibroclassifier is also presented, which is based on the principle of using the influence – vibration and bubbling of the suspension by air bubbles. Studies of the separation process and distribution of fractions in multidisperse liquid on a vibroclassifier of complex action were performed. The obtained theoretical and graphical dependences allowed to establish changes in the parameters of the velocity of sand and amber particles in the bath of the vibroclassifier on the size of fractions and density of the suspension, focusing on the size of amber up to 5mm. At the same time, the problem of determining the dependence of the transition coefficient from the rate of free to the rate of compressed deposition on the density of the suspension and the size of the fractions was solved. Dependencies have been established that have a theoretical justification for the physical process and that describe the experimental data on the Rayleigh curve.

An airborne micro-TEM and physics deep learning solution to near-surface corrections in sand-covered areas

Sand-covered areas, such as desert environments, pose challenges to seismic imaging for resource exploration and monitoring. Aeolian sand dunes provide extreme variations of elastic parameters causing, among other effects, nonlinear velocity gradients proportional to compaction. Description and correction for sand velocities is typically performed through empirically derived sand curve functions. Shallow drilling with uphole traveltime measurements represents another established technique for characterizing the thickness of the sand layer. This defines a basal depositional surface across the investigated area to apply the sand correction for seismic processing operations. The accurate definition of the unconformable base of sand is crucial for the application of robust near-surface corrections. An airborne transient electromagnetic solution is proposed, where the acquisition instrumentation, acquisition parameters, and inversion strategies are tuned to the ultra-shallow depth of the target (2–20 m). The data inversion component makes extensive use of a recently introduced physics-driven DL inversion scheme. It enables boosted depth resolution in the resistivity model using all of the available data while achieving an acceptable data misfit to honor the propagation of the electromagnetic radiation. The imaged resistivity boundary provides an excellent match to the existing uphole data and indicates the presence of long-wavelength mismatch from the previously interpreted base of sand.

Effects of Particle Shape on the Shear Wave Velocity and Shear Modulus of 3D Printed Sand Analogs

Isolating the effects of individual particle properties (e.g. shape, size, mineralogy, surface roughness) on the mechanical behavior of naturally occurring coarse-grained soils is a significant challenge in experimental studies. This challenge can be addressed by recent advances in 3D printing technology which enable generation of artificial sand-sized particles with independent control over particle size and shape. In this study, bender element tests are conducted to examine the isolated effects of particle shape on the shear wave velocity and shear modulus of 3D printed sand analogs. The experimental results show that the shear wave velocity and shear modulus of the 3D printed sand specimens exhibit a relationship with mean effective stress that is in agreement to that reported for natural sands. The specimens composed of 3D printed sands with greater particle roundness and sphericity exhibit greater shear wave velocity and shear modulus for a given void ratio, relative density, and mean effective stress. The changes in shear wave velocity can be captured in terms of differences in individual particle shape parameters such as roundness and sphericity as well as combined particle shape parameters such as regularity. Regression analysis is used to develop relationships between shear wave velocity and particle shape parameters and void ratio, which are shown to be in agreement with previously-published relationships and to reliably predict the shear wave velocity of natural sands. The results presented herein highlight the usefulness of testing 3D printed soils to identify functional trends and dependencies between soil response parameters and intrinsic properties. However, this requires verification of the results against published trends and assessment of the possible effects of the differences in constituent material between the 3D printed and the natural soils.

A new flow velocity measurement method based on the ring electrostatic sensor

Gas-solid two phase flow widely lies in industry process, while its parameters measurement (flow velocity, the mass flowrate, particle sizes, et al.) is very difficult. This paper mainly studies the solid phase flow velocity measurement questions of gas-solid two phase flow with the ring electrostatic sensor. During the flow velocity measurement study, a new mathematical model of the electrostatic sensor is established, and by simulating the obtained model the spatial filter characteristics of the electrostatic sensor are obtained. By the spatial filter characteristics analysis of the ring electrostatic sensor, a new flow velocity measurement method is obtained in this paper. At last, some experiments are accomplished in the laboratory with line sand. The new method of measuring flow velocity is effective in these experiments. The flow velocity obtained with the new measuring method is calibrated with the cross-correlation velocity. When the line sand velocity is less than 7m/s, the repeatability error of the measured velocity is less than ± 10%.

Laboratory-Based Correlation between Liquefaction Resistance and Shear Wave Velocity of Sand with Fines

This paper presents the results of a laboratory investigation into the effect of non-plastic fines on the correlation between liquefaction resistance and the shear wave velocity of sand. For this purpose, undrained stress-controlled cyclic triaxial and bender element tests were performed on clean sand and its mixtures with non-plastic silt. It is shown that the correlation between liquefaction resistance and shear wave velocity depends on fines content and confining effective stress. Based on the test results, correlation curves between field liquefaction resistance and overburden stress corrected shear wave velocity for sand containing various contents of fines are derived. These curves are compared to other previously proposed by field and laboratory studies.

Velocity measurement of North Sea heavy oil sands under changing pressure and temperature

The factors of rock components and reservoir conditions have significant influences on the elastic properties of heavy oil sands. We investigate the effects of these factors on the velocities of heavy oil sands from North Sea through measuring the velocities under changing pressure and temperature conditions. To inspect the influences of heavy oil and gas in pore space, we clean the samples (remove oil) and measure the corresponding velocities under dry and water-saturated conditions, and perform the measurements under as-is and fully saturated conditions. Besides, we also compare the measurements under changing confining and pore pressures, revealing that the increase of water bulk modulus is nonnegligible when pore pressure is large. Our results show that the velocities of oil sands increase with pressure and decrease with temperature while the Vp/Vs ratios show the opposite trends. The comparison of dry and water-saturated measurements suggests that rock frame is weak and oil sands properties are mainly affected by heavy oil. The as-is and fully saturated measurements comparison reveals the strong gas effect on P-wave velocity. Overall, our results highlight the effects of pressure, temperature, frame, gas, and oil on the elastic properties of heavy oil sands. The findings of this study can help for better understanding of the elastic properties of North Sea heavy oil sands under various conditions, which can facilitate the future rock physics modeling and provide important information for seismic characterization of North Sea heavy oil reservoir.

Effects of velocity ratio on dynamics of sand-water coaxial jets

Detailed laboratory experiments were performed to study the dynamics and mixing properties of vertically discharged sand-water coaxial jets in stagnant water. The effects of velocity ratio on the fluid dynamics of two-phase coaxial jets were studied. The axial and radial distributions of sand concentration and velocity were measured with an advanced optical fiber probe (PV6), and sand concentration and velocity measurements were formulated based on flow characteristics. The experimental results demonstrated that the axial velocity and concentration decay rate along the mixing zone, a length approximately six times greater than the nozzle diameter, were independent of the velocity ratio, Ru. Beyond the initial mixing zone, the axial decay rate of sand concentration increased with increasing velocity ratio and became similar to the concentration decay rate of slurry jets. The axial velocity decay of sand-water coaxial jets indicated an inverse relationship with velocity ratio: velocity decay rates decreased with increasing Ru. Experimental observations of sand-water coaxial jets showed that the spreading rate of coaxial jets decreased with increasing velocity ratio; for the coaxial jet with the highest Ru, the spreading rate reached the spreading rate of slurry jets. The integral quantities of jets such as mass and momentum fluxes were calculated using sand concentration and velocity profiles. Average drag coefficients were calculated using momentum balance and proposed equations for sand velocity and concentration. The variations of drag coefficient and interparticle collision parameter indicated that the particle grouping effect reduced the drag coefficient in sand-water coaxial jets with lower velocity ratios. The axial variations of the interparticle collision parameter indicated a strong correlation with velocity ratio. The strong correlation between velocity ratio and the mixing properties of sand-water coaxial jets suggests the velocity ratio is an effective design parameter to control and optimize particle mixing in stagnant water.

Full Loop Numerical Simulation of Fluidization Characteristics at Cyclone and Furnace of 110 MW CFB

Circulating fluidized bed (CFB) boiler has strong points with its recognition when operating with low quality coal contrast to pulverized coal boiler. Boiler load could be improved by increasing coal input and air ratio combustion adjustment. That is why ratio combustion between secondary and primary air is one of valuable parameters influencing fluidization of CFB Boiler. CFB boiler is consist mainly of a furnace, two cyclones, and forced loop pipes, where cyclones are boiler parts that were indicated to have high velocity fluidization up to 30 m/s. Full loop 3D simulation of CFB with focusing on the furnace and cyclone by using computational fluid dynamic (CFD) program was implemented using Eulerian multiphase model to investigate sand volume of fraction, air, and sand velocity including pressure distribution around Cyclone. Several air ratio combustions between primary and secondary air were simulated such as 55%-45%, 50%-50% with 63%, and 100% load variations. It was shown that operation with air combustion ratio 50%-50% and 55%-45% leads to good fluidization at 63% load, while 100% and 110% fluidization will cause an abundant sand entered to inlet cyclone and induce higher sands and air velocity.

Effect of shearing history on stress wave velocities of sands observed in triaxial compression tests

For the accurate design of geotechnical structures subjected to static and dynamic loadings, precise estimation of elastic wave velocities and hence, small strain stiffness of soil is essential. However, the interpretation of elastic wave velocities propagating in deformed/sheared soil has not been comprehensively explored. In this research, shear (Vs) and compression wave velocity (Vp) measurements have been undertaken on three kinds of uniformly graded sands during drained triaxial compression by keeping minor principal stress constant. Planar piezoelectric transducers have been used to overcome the limitations associated with the more commonly used bender elements, such as distortion of transducers during specimen shearing. This technical note reveals that the increase of major principal stress in the wave propagation direction has a more significant influence on Vp in comparison to Vs. The axial strain (εa) at which peak Vs is noted is comparable to the εa at which specimen dilation or phase transformation takes place. The Vs values show a substantial drop after phase transformation, although there is an increase in the mean stress level. However, Vp increases even after specimen dilation takes place, and it is the major principal stress that dictates its evolution during triaxial compression. Moreover, for a given material and initial stress level, elastic wave velocities of specimens prepared at different initial densities approach one another during shearing and later merge at a large εa.

Effects of water saturation and distribution on small-strain stiffness

The purpose of this study is to investigate the role of the degree of saturation and water distribution patterns on small strain soil properties. First, we measure P- and S-wave velocities of fine sands mixed with varying degrees of water saturation Sw = 0, 5, 30, 60, and 100% during the vertical loading under zero-lateral strain conditions. Next, we use a simple geometry analysis combined together with soil index properties to provide the first-order approximation of capillary pressure. Then, we consider the effect of capillarity on soil skeleton stiffness to analyze the data in the context of Gassmann's framework. Finally, we investigate the effect of water distribution patterns on small strain soil properties. Results show that water distribution pattern is a critical factor to control the low perturbation soil properties. Furthermore, a specific surface appears to be a good indicator to predict the effective stress- and pore size-dependent capillary pressure in the determination of small strain geophysical properties.

Elastic wave velocities of hydrate-bearing sands containing methane gas bubbles: Insights from CT-acoustic observation and theoretical analysis

The elastic wave velocities of hydrate-bearing sediments (HBS) are considerably affected by the content of free gas and hydrate. Although several existing models relate the free gas and hydrate saturation to acoustic velocities, the accuracy of these models is still uncertain because of the difficulty in determining the gas content. In this study, we acquired the gas volume fraction and acoustic velocity data of the hydrate-bearing sands through a X-ray computed micro-tomography (CT) and an ultrasonic apparatus, respectively. The acoustic velocities increase slowly at low hydrate saturation (Sh < 33%), whereas they increase rapidly when hydrate saturation exceeds 33%. Using the measured data, we verified three commonly used velocity models, namely, the Biot-Gassmann theory by Lee (BGTL), effective media theory (EMT), and simplified three-phase equation (STPE). The results obtained using the BGTL are consistent with the experimental results when hydrate saturation exceeds 45%, while the EMT-B model is more suitable for predicting P-wave velocity (Vp) when the hydrate saturation varies from 15% to 55%. The value of Vp calculated by the STPE model, without considering the effects of gas on velocity, is higher than the experimental value. We further applied a new method combining the Wood and Domenico equations to calculate the bulk modulus of HBS containing methane gas, which can improve the precision and applicability of the STPE model. Compared with the EMT and BGTL models, the modified STPE model is more suitable for predicting Vp of unconsolidated reservoirs with high porosity and permeability. These results provide a new method for further experimental research and a theoretical reference for accurately estimating hydrate saturation through logging data during natural gas exploration and development.

Numerical simulation and experimental study of aeolian sand load under aeolian sand environment

Concrete structures in a sandstorm environment suffer from sandstorm erosion for a long time, which reduces the durability of concrete buildings, and then threatens the safety of buildings. Therefore, it is of great practical significance to study the aeolian sand load under the aeolian sand environment. In this paper, by numerical simulation of the sand load on the surface of bridge and simulation test of the sand load on the surface of the concrete in the sand environment, the variation law of the sand load under different sand parameters is studied. Through comparative analysis, it is concluded that the variation law of aeolian sand load in numerical simulation and test tends to be consistent with the variation of aeolian sand velocity and sand content ratio.

Electrical resistivity and elastic wave velocity of sand–cement–inorganic binder mixture

Cement-based grout has been used for ground improvement. Owing to environmental issues related to cement, its usage should be reduced. In this study, an inorganic binder is introduced to reduce the use of cement in grout. To evaluate the transient electrical and mechanical properties of the sand–cement admixture samples improved with the addition of inorganic binders, two non-destructive testing methods, the electrical resistivity and free–free resonant column tests, were adopted in addition to the unconfined compressive strength (UCS) test. Experimental tests were performed considering four different mixing ratios and three different cement contents, depending on the curing time. The results show that the mixing ratio and curing time have considerable effects on the electrical and mechanical properties of the mixture. The UCS decreases as the cement content decreases. However, sufficient UCS is expected to be obtained when the inorganic binder content is increased in the mixture. From the results, it is found that geotechnical properties of the mixture can be estimated in the field with proper non-destructive testing methods. It is expected that the data and trends proposed in this study can be used as a reference in predicting grouting quality in the field.

Experimental investigation of the performance of a shell-and-tube particle-to-air heat exchanger

The paper presents an experimental study of the heat characteristics of the bulk flow of red sand over diamond-shaped tubes in a particle-to-air heat exchanger (PAHX). The objective of this work is to demonstrate the suitability of solid particles as a working medium in applications such as concentrating solar power (CSP). The tests are conducted at the experimental central receiver facility at King Saud University in Riyadh, Saudi Arabia. The PAHX is a custom-made heat exchanger in which the particle flow rate can be controlled by a slide gate at the bottom. A custom-made (100 kWe) microturbine is used to heat the particles inside the PAHX as they are circulated inside a tower by a lifting system. Experiments are conducted to investigate the effect of the particle flow rate (particle velocity) on the heat transfer coefficient on the sand side. The results show that the particle velocity strongly affects hsand. Increasing the sand velocity by less than 20% can cause an increase of more than 100% in hsand. The maximum hsand value of 84 W/m2·°C is obtained at the maximum particle velocity of 0.71 mm/s. However, this value is expected to increase when slightly smaller particles with more uniform shapes are used.

A Numerical Study of Aeolian Sand Particle Flow Incorporating Granular Pseudofluid Optimization and Large Eddy Simulation

A numerical investigation of aeolian sand particle flow in atmospheric boundary layer is performed with a Eulerian–Eulerian granular pseudofluid model. In this model, the air turbulence is modelled with a large eddy simulation, and a kinetic–frictional constitutive model incorporating frictional stress and the kinetic theory of granular flow is applied to describe the interparticle movement. The simulated profiles of streamwise sand velocity and sand mass flux agree well with the reported experiments. The quantitative discrepancy between them occurs near the sand bed surface, which is due to the difference in sand sample, but also highlights the potential of the present model in addressing near-surface mass transport. The simulated profiles of turbulent root mean square (RMS) particle velocity suggest that the interparticle collision mainly account for the fluctuation of sand particle movement.

Multicomponent Water Effects on Rotating Machines Disk Erosion

When sand particles are entrained into carrier flow, such as liquid, a strong interaction occurs with the surface of the metallic material, resulting in serious erosion damage. However, the effect of the physical properties of particles and materials on erosion characteristics has not been well studied. In this paper, the erosion-wear behavior of a rotating disc surface under the action of solid–liquid two-phase flow was studied by using the discrete particle model (DPM). The wear effects on the surface of sample due to particle diameter (d = 0.1 mm, d = 0.2 mm, d = 0.3 mm, d = 0.4 mm), particle volume fraction (CV = 2%, CV = 3%, CV = 4%, CV = 5%), and particle inlet velocity (v = 1.05 m/s, v = 2.05 m/s, v = 3.05 m/s, v = 4.05 m/s) were analyzed using representative values of operating conditions of rotating machines. The results show that the wear amount increases exponentially with the radius, whilst the maximum wear amount increases faster than the average wear amount with the particle volume fraction. The surface wear grows inversely with the particle diameter but slightly with the particle inlet velocity. A case study of stainless steel samples at different radius positions on the surface of rotating disc is carried out using a mixed velocity of sand and water of 2.05 m/s, an average particle size of 0.1 mm, and a concentration of CV = 2.5%. The experiments show the wear amount increases with the radius on the surface of the rotating disc, just as predicted by the numerical simulation. Two important findings emerge from the study: (1) the wear morphology of the specimen surface develops from two to three regions; (2) when the basal body is rotating at high speed, the wear degree is influenced more by the circumferential than particle inlet velocity. The wear morphology was observed by using a scanning electron microscope (SEM). It exhibited a mixture of fine and coarse scratches and pits, and the distribution of these varied according to the radial distance of the disc.