Particle Lift Research Articles

Predictive modelling of drag, lift and torque coefficients of cylindrical biomass particles under artificial intelligence

The escalating threats of climate change and fossil fuel depletion have greatly spurred the widespread utilization of renewable energy sources. Biomass energy stands out as the most abundant renewable energy resource. Among all biomass conversion technologies, direct combustion of biomass for heating and power generation represents the most common and cost-effective approach. Suspended combustion technology is widely employed in existing biomass combustion power plants worldwide. However, conventional modeling procedures often fail to adequately address the differences between coal and biomass combustion, particularly the significant impact of large-sized and highly non-spherical cylindrical straw biomass particles on their trajectories. This study utilizes OpenFOAM-body-fitted mesh direct numerical simulation (DNS) to generate a Computational Fluid Dynamics (CFD) dataset consisting of 300 data points for cylindrical particles, aimed at constructing a prediction model based on machine learning (N+1) for key aerodynamic parameters (drag coefficient, lift coefficient, and torque coefficient). The proposed model enables precise prediction of aerodynamic parameters for a wider range of different cylindrical particles and flow conditions, thus extending the existing Euler-Lagrangian model for non-spherical biomass multiphase flow.

Drag, lift, and torque correlations for axi-symmetric rod-like non-spherical particles in linear wall-bounded shear flow

This paper presents novel correlations to predict the drag, lift, and torque coefficients of axi-symmetric non-spherical rod-like particles in a wall-bounded linear shear flow. The particle position and orientation relative to the wall are varied to systematically investigate the influence of the wall on the hydrodynamic forces. The newly derived correlations for drag, lift, and torque on the particle depend on various parameters, including the particle Reynolds number, the orientation angle between the major axis of the particle and the main local flow direction, the aspect ratio of the particle, and the dimensionless distance from the particle centre to the wall. The impact of the wall on the hydrodynamic forces is accounted for as a function of a multiplication factor on the drag force in case of locally uniform flow, and an additional force contribution for the lift and the torque, modifying the resultant forces experienced by a particle in a locally uniform flow. The changes in the hydrodynamic forces prove to be substantial, emphasizing the necessity of accounting for wall effects across all particle types and flow conditions investigated in this study. The coefficients of the correlations are determined through a fitting process utilizing the data generated from our previous study on the interaction forces between a locally uniform flow and an axi-symmetric non-spherical rod-like particles, as well as from data of novel direct numerical simulations (DNS) performed in this work of flow past axi-symmetric rod-like particles near a wall. The proposed correlations exhibit a good agreement compared to the DNS results, with median errors of 2.89%, 5.37%, and 11.00%, and correlation coefficients of 0.99, 0.99, and 0.96 for the correlations accounting for the drag, lift, and torque coefficients of a non-spherical particle in wall-bounded linear shear flow profile, respectively. These correlations can be used in large-scale simulations using an Eulerian–Lagrangian or a CFD/DEM framework to predict the behaviour of axi-symmetric rod-like non-spherical particles in wall-bounded shear flow to locally uniform flow conditions.

Finer Measurement Scales for Induced Hydrophobicity Using the Water Droplet Penetration Test

The Water Droplet Penetration Test (WDPT) is commonly used in most soil water repellency (SWR) research and is particularly prominent in field studies after wildfire events. Suppose a water droplet does not infiltrate the soil within the first five seconds. This soil is considered to contain some degree of water repellency, classified by the overall penetration time. Our results show an inflection point in the plot of the height of a droplet vs. droplet penetration time during a WDPT trial. This inflection point is indicative of a combination of two possible flow patterns influencing droplet penetration, one governing and the other—caused by particle lift—drastically impeding the infiltration rate. The reorganization of the intrinsic particle lift at the air–water interface leads to contact angles hindering the expected penetration, delaying the expected infiltration rate to degrees larger than a continuously flat porous hydrophobic surface would. The particle lift creates an instability that can create two competing regimes, leading to two sets of water droplet penetration times. The similarity among sorptivity values for coarse grains at higher hydrophobicity levels, medium grains at intermediate hydrophobicity levels, and fine grains at lower hydrophobicity levels suggests that interpretation of the WDPT needs to be adjusted based on grain size.

Anomalous electrohydrodynamic cross-stream particle migration

Particle cross-stream migration in electrohydrodynamic microfluidic systems exhibits intriguing behaviors, which makes it interesting when viewed from a fundamental perspective and promising for nanoparticle focusing and separation applications. So far, particle behavior in such systems has been explained with the slip-induced lift force model (Saffman model), which predicts particle central or side focusing based on the direction of electric field and fluid flow. However, in our previous work, we observed particle migration patterns that did not adhere to the prediction of the Saffman model. In this work, we further studied this novel particle lateral migration behavior, which we termed the “anti-Saffman” behavior. We experimentally investigated how changing the conductivity of the suspending medium influences particle behavior and quantitatively measured the net lateral force experienced by the particles. Then, we compared this net force with the prediction of the relevant lift force models in the literature. We concluded that the anti-Saffman behavior is positively correlated with medium conductivity and shear rate (∝γ̇2). Furthermore, the comparison with the existing force models revealed that none of them can predict the experimentally observed particle lift. The net lift predicted by hydrodynamic lift models indicated that the underlying mechanism behind our experiments also potentially has a hydrodynamic origin. We believe this phenomenon offers the possibility of manipulating and separating nanoparticles suspended in standard aqueous electrolyte solutions, which makes it applicable to various biological samples.

Drag, lift and torque correlations for axi-symmetric rod-like non-spherical particles in locally linear shear flows

This paper derives new correlations to predict the drag, lift and torque coefficients of axi-symmetric non-spherical rod-like particles for several fluid flow regimes and velocity profiles. The fluid velocity profiles considered are locally uniform flow and locally linear shear flow. The novel correlations for the drag, lift and torque coefficients depend on the particle Reynolds number Rep, the orientation of the particle with respect to the main fluid direction θ, the aspect ratio of the rod-like particle α, and the dimensionless local shear rate G̃. The effect of the linear shear flow on the hydrodynamic forces is modeled as an additional component for the resultant of forces acting on a particle in a locally uniform flow, hence the independent expressions for the drag, lift and torque coefficients of axi-symmetric particles in a locally uniform flow are also provided in this work. The data provided to fit the coefficient in the new correlation are generated using available analytical expressions in the viscous regime, and performing direct numerical simulations (DNS) of the flow past the axi-symmetric particles at finite particle Reynolds number. The DNS are performed using the direct-forcing immersed boundary method. The coefficients in the proposed drag, lift and torque correlations are determined with a high degree of accuracy, where the mean error in the prediction lies below 2% for the locally uniform flow correlations, and bwlow 1.67%, 5.35%, 6.78% for the correlation accounting for the change in the drag, lift, and torque coefficients in case of a linear shear flow, respectively. The proposed correlations for the drag, lift and torque coefficients can be used in large-scale simulations performed in the Eulerian-Lagrangian framework with locally uniform and non-uniform flows.

Side-by-Side Testing of Grit Separation Units

Two grit removal systems were tested side-by-side for the treatment of wastewater from a combined-sewer system. The two units were operated at constant flows and variable grit loads ranging from 1.2 to 745 Kg/m3 /h that covered the typical range of dry and wet weather conditions experienced at the treatment facility. The average mass grit removal for the multi-tray free vortex unit was 92.6% and it was 85.4% for the forced vortex system. Both units consistently failed to remove particles with sand equivalent sizes, which their respective overflow rates would otherwise predict. This observation can be explained by uneven force distributions over non-spherical grit particles with lumpy grease deposits and variable curvature that effect motion traverse to flow, increase buoyancy and cause particle lift.

Direct numerical simulation of the drag, lift, and torque coefficients of high aspect ratio biomass cylindrical particles

Biomass straw fuel has the advantage of low-carbon sustainability, and therefore, it has been widely used in recent years in coupled blending combustion with coal-fired utility boilers for power generation. At present, the drag force FD, the lift force FL, and the torque T evaluation model are very limited. In this study, within a wide range of Reynolds numbers (10 ≤ Re ≤ 2000) and incident angles (0° ≤ θ ≤ 90°), the computational fluid dynamics open source code OpenFOAM-body-fitted mesh method is used to carry out the direct numerical simulation of the flow characteristics of large cylindrical biomass particles with a high aspect ratio of L/D = 9:1. The results show that (1) the projected area of the cylinder begins to decrease after reaching the maximum at θ = 15°, while the change in the incident angle causes the formation of a smaller recirculation zone on the leeward side of the structure, and the effect of the pressure difference on the drag coefficient (CD) is reduced. (2) The lift coefficient (CL) displays a parabolic symmetric distribution when θ = 45°, and then the distribution becomes asymmetrical when Re > 100. The torque coefficient (CT) exhibits a similar trend. (3) Based on the simulation data and the literature data, new models for CD, CL, and CT for cylinders with L/D = 9:1, 10 ≤ Re ≤ 2000 and 0° ≤ θ ≤ 90° are obtained, and the mean square errors are 2.4 × 10−2, 1.4 × 10−2, and 6.4 × 10−2, respectively. This new model can improve the accuracy and adaptability of the universal model of gas–solid dynamics for biomass particles.

Concentration-polarization electroosmosis for particle fractionation.

Concentration-polarization electroosmosis (CPEO) refers to steady-state electroosmotic flows around charged dielectric micro-particles induced by low-frequency AC electric fields. Recently, these flows were shown to cause repulsion of colloidal particles from the wall of a microfluidic channel when an electric field is applied along the length of the channel. In this work, we exploit this mechanism to demonstrate fractionation of micron-sized polystyrene particles and bacteria in a flow-focusing device. The results are in agreement with predictions of the CPEO theory. The ease of implementation of CPEO-based fractionation in microfluidics makes it an ideal candidate for combining with current techniques commonly used to generate particle lift, such as inertial or viscoelastic focusing, requiring no extra fabrication steps other than inserting two electrodes.

Numerical investigation of three-dimensional flow over dual particles during settling

This study investigates three-dimensional flow over dual particles at various separation distances and Re, mainly focusing on the particle's lift behavior in close proximity. Minimal changes in separation distance can result in various unique flow patterns and a non-linear augmentation in lift coefficient. Additionally, quantifying flow blockage between two particles suggests that repulsion behavior and blockage phenomenon are not mutually inclusive. Transient simulations suggest that periodic vortex shedding is not only a function of Re and separation distance, but they also suggest the existence of multiple combinations of separation distance and Re at which the shedding mechanism is triggered. Evident periodic vortex shedding was quantified at 0.25D and Re = 250, while miniature periodic instabilities at the same Re but for a larger separation distance (0.5D). An observable inverse relationship between lift and separation distance exists, while different patterns were quantified for the variation of lift at different Re.

Uninterrupted lift of gas, water, and fines in unconventional gas wells using foam-assisted artificial lift

Sustainable and clean production of natural gas is of paramount importance in transitioning to a low-emission economy. Gas production in an unconventional well such as a coal seam gas (CSG) relies on continuous dewatering, commonly performed through a progressive cavity pump (PCP). PCPs are susceptible to failure for different reasons, primarily the interference of solid particles. This results in interruptions, pump replacement, well cleaning and recommissioning which pose long downtimes (i.e., reduced well deliverability), work-over at substantial costs, along with environmental impacts such as increased methane emissions to the atmosphere.This paper aims to demonstrate and assess the performance and suitability of a sustainable dewatering technique, referred to as foam-assisted gas lift (FAGL) which offers uninterrupted dewatering, minimal downtime and minimised environmental impacts. FAGL is capable of maintaining the gas well deliverability by replacing the downhole pump with a gas compressor at the surface and an engineered gas-liquid-solid flow dynamics by injecting foamers and a small amount of surplus gas into the wellbore.The performance of FAGL is evaluated in 45 vertical CSG wells in Australia under different operating conditions and depths ranging between 400 and 1050 m and is compared with well data using PCPs. The flowing bottomhole pressure (FBHP) is calculated to assess the suitability of FAGL under different operating conditions. The results from this study show that FAGL outperforms PCPs in more than 50% of the cases under this study, offering on average 34% lower FBHP. The FAGL's capability in lifting solid particles is demonstrated using solids taken from gas wells in Queensland, showing a reliable and continuous lift of particles. In addition, chemical defoaming of the foam at the surface is demonstrated to avoid re-foaming in the downstream and mitigate the risk of contamination of the surrounding area.

The study of the separation and deposition of dredging soil slurry under physical disturbance.

Most existing research uses experimental designs for testing, which cannot efficiently analyse the migration and sorting rules of particles in the disturbed slurry. Therefore, based on the fluidized bed flow film theory, a slurry flow film structure system is established according to the disturbance state of the fluid. On this basis, the particle size and distribution law of the disturbing force formed by slurry disturbance are analyzed, and the calculation model of single particle lift in the flowing film is also analyzed. On this basis, using Markov probability model, the probability of particle lifting and sorting between layers is theoretically deduced. Then, according to the particle ratio of the original mud, the settlement gradation of the particles in the disturbance is analyzed. It can also predict the separation degree of particle in natural turbulence, fluidized beds, and sludge mechanical dewatering. Finally, according to the particle flow software PFC (Particle Flow Code), the main influencing parameters (disturbing force and gradation) were verified and analyzed. The results show that the particle flow simulation results are in good agreement with the calculation results. The model of slurry membrane separation proposed in this paper can provide a basis for studying the mechanism of slurry disturbance separation and particle deposition.

Thermal Creep on Mars: Visualizing a Soil Layer under Tension

At low ambient pressure, temperature gradients in porous soil lead to a gas flow called thermal creep. In this regard, Mars is unique as the conditions for thermal creep to occur in natural soil only exist on this planet in the solar system. Known as a Knudsen compressor, thermal creep induces pressure variations. In the case of Mars, there might be a pressure maximum below the very top dust particle layers of the soil, which would support particle lift and might decrease threshold wind velocities necessary to trigger saltation or reduce angles of repose on certain slopes. In laboratory experiments, we applied diffusing wave spectroscopy (DWS) to trace minute motions of grains on the nanometer scale in an illuminated simulated soil. This way, DWS visualizes pressure variations. We observe a minimum of motion, which we attribute to the pressure maximum ∼2 mm below the surface. The motion above but especially below that depth characteristically depends on the ambient pressure with a peak at an ambient pressure of about 3 mbar for our sample. This is consistent with earlier work on the ejection of particle layers and is in agreement with a thermal creep origin. It underlines the supporting nature of thermal creep for particle lift, which might be especially important on Mars.

Numerical Investigation of Particle Focusing Patterns in Laminar Pipe Flow With High Reynolds Numbers

The inertial focusing characteristics of particles in laminar flow pipes with high <i>Re</i> numbers were studied based on the “relative motion model”. In order to solve the problem of long pipes with high <i>Re</i> number flow, periodic boundary conditions were imposed on the inlet and outlet of the pipe. The research results show that the use of periodic boundary conditions can effectively reduce the computational, and the mechanical properties of particles in high <i>Re</i> flow can be calculated by using <i>L</i>=4<i>D</i> pipe. The difference from the low <i>Re</i> number is that as the <i>Re</i> number continues to increase,the lift force of the particles in the radial direction is no longer distributed as a parabola. The lift curve has a concave area between <i>r</i>⁺ =0.5 ~ 0.7, and there is a tendency for a new inertial focus point to appear in this section. By means of particles of <i>a</i>⁺ =1/17 for <i>Re</i> &gt; 1 000, this new focus point position is solvable. In addition, in the analysis of the flow field, a secondary flow occurs around the particle, and its intensity gradually increases with the <i>Re</i> number and the closeness of the particle to the wall. The generation of the secondary flow affects the spatial distribution of the particle lift.

Determination of the lifting height of dust particles after a mass explosion in an iron ore open pit

Open pit mining is accompanied by emissions of fine dust and hazardous gases into the atmosphere. This is related to the operation of open pit transport, drilling and blasting operations. The release of harmful components into the quarry space and the increase in their concentrations has a negative impact on the health of working personnel and leads to pollution of the environment. In doing so, the nature of fine dust and gases pollution depends on the mining technology and meteorological factors. The problem of reduced effectiveness of dust suppression methods after mass explosions in open pits is relate to insufficient research into the formation of dust and gas cloud. Additional theoretical and experimental research into the dust dynamics of blasting operations is therefore need. The article discusses the stages of formation of the dust and gas cloud after a mass explosion in an iron ore open pit. The results of experimental studies of the evolution of the dust and gas cloud at different points in time after the detonation of borehole charges are presented. Relations for determination of density and dynamic viscosity of gases, gas mixture and gas-dust aerosol are given. A formula for determining the time and height of ascent of spherical dust particles at the dynamic stage of dust and gas cloud formation is obtain. In this case, the assumption is madid that there is no mutual influence of the dynamic and thermal factors after detonation of the charges. The elevation of dust particles due to temperature differences during the heat stage of dust and gas cloud formation is determined. Based on the analysis of the calculation results, the duration of the dynamic stage of cloud formation is determined. It is established that, following the release of solid and gaseous detonation products into the atmosphere, a height distribution of dust particles is observed as a function of their diameter. That said during, the dynamic stage of dust and gas cloud formation, the height of dust particle lift is directly proportional to their diameter, while during the heat stage the inverse relationship is observe. That at the beginning of the thermal stage the deposition of coarse dust particles takes place are established. In this process, fine dust particles rise to a maximum height and are then carried outside the open pit by the airflow.

Experimental study of particle lift initiation on roller-compacted sand–clay mixtures

Civil engineering works are sources of dust emissions, which can cause severe security, health and environmental damages to workers and neighbourhoods. This is particularly significant for implementation of earthwork sites. The present paper reports a study conducted to characterise the soil–atmosphere interaction above compacted soils where particle lift is initiated. Mixtures of kaolin clay and sand have been compacted using a laboratory roller compactor that reproduces near-field compaction conditions. Shear testing conducted at the interface confirms that the sand content affects the friction angle between the soil and the compaction roller. The experimental velocity profiles above the compacted samples have been obtained in a wind tunnel using a non-intrusive measurement technique (laser Doppler velocimetry). Results show that the sand fraction affects velocity profiles. Compaction, therefore, may not fully reduce the roughness of the soil surface. The airflow friction velocities at the sample surfaces have been determined from the boundary layer profiles. The results achieved demonstrate that all tested soils reach the threshold friction velocity required to initiate particle lift, and the higher the sand content of the soil, the more likely it is that particle lift occurs.

Analysis of particle dispersion in a turbulent flow considering particle rotation

Non-spherical particles exist widely in natural and industrial fluid systems and the motions of non-spherical particles are significantly different from that of spherical particles. In this paper, a simplified model of non-spherical particles considering particle drag correction, lift, and rotation was established. Based on the Eulerian–Lagrangian simulation, the dispersion characteristics of spherical and non-spherical particles with different Stokes numbers in a high-speed turbulent jet were analyzed and compared considering the effect of particle rotation. The results show that, the differences in particle dispersion and radial velocity fluctuation between non-spherical particles and spherical particles in the jet are significant, especially when Stokes number is large. Moreover, the effects of different type of forces on the dispersion of non-spherical particles and spherical particles were compared in detail, which revealed that the change of the Magnus force caused by the increase in the angular velocity of non-spherical particles plays a dominant role in the differences of particle dispersion.

Characterization of lift force and torque in prolate ellipsoid suspensions

The paper derives correlations for lift force and fluid torques acting on stationary prolate ellipsoid suspensions of aspect ratio (AR) 2.5, 5, and 10 subjected to uniform flow. Particle Resolved Simulations (PRS) are conducted on a suspension of infinite extent in two directions for Reynolds number 10 ≤ Re ≤ 200 and solid fractions (φ) between 0.1 ≤ φ ≤ 0.3.The suspension-mean lift-to-drag ratio varies between 7% to 14% at Re=10 which increases to 14% ~ 22% at Re=200. The torque-induced tip rotational acceleration can reach 38% ~ 85% of drag-induced translational acceleration at Re = 200. Single particle lift force and torque correlations of (Fröhlich et al., 2020) are modified and adapted to predict current angular-mean lift and torque data. The resulting lift correlation captures the PRS data within an average deviation below 7%. Torque exhibits a somewhat more complex dependency at AR = 10 than the assumed sinθ ∙ cosθ variation but nevertheless the correlations predict angular-mean values with mean relative deviations of 16.6% at AR = 10.

An Experimental Demonstration of the Effective Application of Thermal Energy Storage in a Particle-Based CSP System

Tests were performed at the particle-based CSP test facility at King Saud University to demonstrate a viable solution to overcome the limitations of using molten salt as a working medium in power plants. The KSU facility is composed of a heliostat field, particle heating receiver (PHR) at the top of a tower, thermal energy storage (TES) bin, a particle-to-working fluid heat exchanger (PWFHX), power cycle (microturbine), and a particle lift. During pre-commissioning, a substantial portion of the collected solar energy was lost during particle flow through the TES bin. The entrained air is shown to be the primary cause of such heat loss. The results show that the particle temperature at the PHR outlet can reach 720 °C after mitigating the entrained air issue. Additionally, during on-sun testing, a higher temperature of the air exiting the PWFHX than that of the air entering is observed, which indicates the effective solar contribution. Half-hour plant operation through stored energy was demonstrated after heliostat defocusing. Lastly, a sealable TES bin configuration for 1.3 MWe pre-commercial demonstration unit to be built in Saudi Arabia by Saudi Electric Company (SEC) is presented. This design modification has addressed the heat loss, pressure build-up, and contamination issues during TES charging.

Minimum Velocity of Impingement Fluidization for Parachute-Shaped Vegetables

Accurate calculation of the minimum fluidization velocity makes it possible to reduce raw material losses due to the use of excessively high or excessively low air velocities. This is particularly true for impingement fluidization, which is little studied, especially when treating parachute-shaped raw material. This paper focused on determining the drag coefficient for cauliflower florets, mushrooms, and broccoli. Analysis of the critical particle lift velocity showed that the lowest value of the drag coefficient was found for mushrooms (0.9). The parachute-shaped vegetables analyzed had a large scatter of drag coefficient values associated with their specific shape (standard deviation: mushrooms 0.10 broccoli 0.14, and for cauliflower 0.15). The measured mean values of the minimum fluidization velocity of the tested vegetables in the impingement fluidization method ranged from 6.9 m∙s−1 to 10.97 m∙s−1. Application of the procedure recommended by Shilton and Narajan for calculating the minimum fluidization velocity on the basis of the shape coefficient ε resulted in large discrepancies between the calculated and experimental values (from 2.4 m∙s−1 to 3.8 m∙s−1).

Sensitivity Analysis of the Levelized Cost of Electricity for a Particle-Based Concentrating Solar Power System

Abstract This study presents a sensitivity analysis of the levelized cost of electricity (LCOE) for a particle-based system with the costs of the most current components. New models for the primary heat exchanger, thermal energy storage, and tower are presented and used to establish lower and upper bounds for these three components. The rest of component costs such as particle cost, cavity cost, and lift cost are set to lower and upper bounds estimating an uncertainty between 25% and 50%. Other relevant parameters related to lift and storage performance are also included in the analysis with the same uncertainty. This study also includes an upgrade to the receiver model by including the wind effect in the efficiency, which was not included in previous publications and may have a big impact in the system design. A parametric analysis shows the optimum values of solar multiple, storage hours, tower height, and concentration ratio, and a probabilistic analysis provides a cumulative distribution function for a range of LCOE values. The results show that the LCOE could be below $0.06/kWh with a probability of between 80% and 90%, where the costs of primary heat exchanger, particles, and lifts have largest contribution to the variance of the LCOE.