Upward Velocity Research Articles

Ionosphere response to geospace storm on 25 September 2016 over Kharkiv (Ukraine)

Instrumental observations of variations in the level of the geomagnetic field and ionospheric parameters were conducted during a weak geospace storm on September 25, 2016. It was found that a moderate magnetic storm was accompanied by variations in the level of the H component of the geomagnetic field up to 20–30 nT, as well as variations in the level of fluctuations of the horizontal components of the geomagnetic field up to ±(2–3) nT. It was revealed that the ionospheric storm was three-phase, mostly moderate. The decrease in the electron density reached a factor of 1.5, and its increase reached a factor of 2.2. The increase in the electron temperature during the negative phase of ionospheric storm did not exceed 200–300 K, while its increase during the positive phase of ionospheric storm reached 400–500 K. The ion temperature variations were within ±100 K. During the negative phases of the ionospheric storm, individual deviations in the vertical plasma drift velocity from those on a geomagnetically quiet day were observed both in the direction of decreasing the downward drift velocity (increasing the upward drift velocity at high altitudes) and vice versa. Significant (17–53 m/s) deviations in velocity variations towards positive values (decrease of downward and increase of upward drift velocity), accompanied by the rise of the F2 layer, after significant changing in the zonal component of the magnetospheric electric field (from –2 to 3.5 mV/m), contributed to the increase in the electron density and to the appearance of the positive phase of the ionospheric storm. During the positive phase, the increase in the velocity of downward plasma drift reached 9–20 m/s at altitudes above 450 km. The negative phases of the ionospheric storm were formed due to an increase in the electron and ion temperatures and a decrease in the O/N2 ratio during the storm. The generation of ionospheric storm positive phase at mid-latitudes apparently was caused by several mechanisms at once: a penetrating electric field, a meridional wind directed toward the equator, and downward plasma flows in the protonosphere. The phases of the ionospheric storm were accompanied by significant variations in the dynamic and thermal processes in the ionosphere.

Influence of waves on the three-dimensional distribution of plastic in the ocean

The world's oceans are facing plastic pollution, 80 % of which of terrestrial origin flowing from the mismanaged waste of coastal populations and from river discharge. To study the fate of this pollution, the three-dimensional trajectories of neutral plastic particles continuously released for 24 years according to realistic source scenarios are computed using currents from a global ocean-wave coupled model at 14∘ resolution and from a reference ocean-only model. These Lagrangian simulations show that neutral particles accumulate at the surface in the subtropical convergence zones from where they penetrate to about 250 m depth and strongly disperse over 40∘ of latitude. About 5.3 % of the particles remain at the surface with the wave-coupled model currents, whereas only 2 % for the uncoupled model, with some modulation in the location of the convergence zones. Increased surface retention results from upward vertical velocities induced by widespread divergence of waves-induced Stokes transport in the surface layers.

Numerical study of influence of mould width on freestanding adjustable combination electromagnetic brake in continuous casting mould

A mathematical model was developed to describe the behavior of liquid steel flow and the steel/slag interface at a constant casting throughput in moulds of different widths. The impact of mould width (MW) on the liquid steel flow and the steel/slag interface was analyzed. Further it was examined whether a freestanding adjustable combination electromagnetic brake (FAC-EMBr) was conducive to controlling and improving the liquid steel flow. The results indicate that increasing MW decreased impact strength of the jet, upward backflow, and surface velocity––this was beneficial for reducing the meniscus height. Adjustment of the current intensity would enable the control of the behaviour of the liquid steel flow and meniscus, as well as reduce the dependence on matching the electromagnetic parameters and process parameters. This simplifies the operational process. As the MW increased to 1600 mm, an excessive input current of the vertical pole (IV = 250 A) significantly decreased the upward backflow velocity; this was not conducive to melting the mould powder.

Numerical Simulations of the Thermal Effect on Flow and Dispersion around an Isolated Building

Abstract The effect of temperature on flow and pollutant dispersion around an isolated building was investigated by computational fluid dynamics. First, the accuracy of the standard k–ε turbulence model in simulating the thermal effect on the flow and dispersion was assessed. The results showed that the reattachment of the numerical simulation behind the building was longer than that in the experiment because it could not reproduce the periodic fluctuations in the wake region and that the momentum transfer in the lateral direction was underestimated. Despite this, the temperature and concentration of the numerical simulation were in good agreement with the experimental results. Then, the standard k–ε turbulence model was adopted to investigate the effect of the ground temperature on flow and dispersion. The result indicated that, with the increase in temperature, the reattachment length behind the building significantly decreased and the vertical upward velocity increased, suggesting that rising temperature changed the flow. As the flow changed, the pollutant dispersion also changed. The pollutant plume depth increased while its width decreased with increasing ground temperature. It can be seen from the pollutant flux analysis that both convective transport and turbulent transport play important roles in vertical dispersion. The influence of ground temperature on convective motion was more obvious than that on turbulent motion because of the changed airflow. Significance Statement (i) The accuracy of the standard k–ε turbulence model in simulating the thermal effect on the flow and dispersion was assessed. The results showed that the reattachment of the numerical simulation behind the building was longer than that in the experiment because it could not reproduce the periodic fluctuations in the wake region and that the momentum transfer in the lateral direction was underestimated. Despite this, the temperature and concentration of the numerical simulation were in good agreement with the experimental results. (ii) Rising temperature not only increases turbulent motion but also alters airflow and pollutant plume morphology.

Impact of transported dust aerosols on precipitation over the Nepal Himalayas using convection-permitting WRF-Chem simulation

In this study, we implemented a convection-permitting Weather Research and Forecasting model coupled with chemistry (WRF-Chem) to assess the impact of the long-range transported dust aerosols on the precipitation and convective processes over the Nepal Himalayas. A substantial amount of dust aerosol was transported to the Central Himalayan region during the dust storm event that occurred from 12 to 15 June, 2018 in the Thar desert, northwestern India. Two different sensitivity simulations, with and without transported dust aerosols, in a cloud-resolving scale of 3 km horizontal resolution was performed. We isolated the long-range transported dust aerosols by zeroing out dust aerosols from lateral boundary conditions and keeping all other locally emitted and remotely transported aerosols from anthropogenic, biogenic, and biomass burning sources. The simulation results show the noticeable impacts of transported dust aerosols on the cloud microphysical properties and regional precipitation over the southern slopes of the Nepal Himalayas. In comparison to the simulation without dust, precipitation is enhanced by 9.6% over the mountainous terrains (500–3000 m) in the presence of dust aerosols. An activation of dust aerosols as condensation nuclei significantly increased the droplet concentration resulting in enhanced convection and upward velocity with the release of latent heat of condensation. Though we simulated one event of long-range transported dust aerosols and some biases in simulation exist, this study highlights the discernible impact of remote dust aerosol on the convection and cloud microphysical properties, which can significantly influence the regional precipitation and Himalayan hydrology.

Lattice Boltzmann simulation of droplet impact dynamics on superhydrophobic surface decorated with triangular ridges

The rapid rebound of droplets impacting on superhydrophobic surfaces is used in a wide range of applications such as anti-icing, anti-forcing and self-cleaning. In this study, the droplet impacting a superhydrophobic surface equipped with macroscopic triangular ridges is simulated using the three-dimensional lattice Boltzmann method (LBM) and focus on the effects of Weber number (We) and the number of ridges on the dynamic behavior and contact time. For the single ridge, as We increase, the droplet gradually form a ring shape and the splits. The appearance of ring shape leads to a rapid decrease in contact time t * , which is because an opposite fluid movement in the inner and outer edges collides with each other and generate an upward velocity that facilitate the droplet bouncing. Base on the single ridge, the structure of cross ridges and quadruple ridges are proposed to research the effect of different number of ridges to the contact time. It can be found that the contact time and phenomenon between cross and quadruple ridges are similar, and the contact time decreases by about 50–66.7 % substantially and has a limited time compared to the single ridge, although there is no break or ring forming before they rebound. Therefore, the crossed ridges(collective name for cross and quadruple ridges) structure helps to reduce the contact time of droplets impacting the superhydrophobic surface, but an excessive number of ridges should be avoided.

Design and flow field analysis of impregnated diamond bit for seafloor drill in soft-hard interlaced strata

According to the seafloor drill working conditions and the complex formation characteristics of the seafloor, this paper aims to improve the adaptability of the diamond bit to the formation and the coring quality. The cutter tooth design scheme of the impregnated diamond bit is proposed, and Fluent analyzes the flow field of drilling fluid at the bottom hole. The results show that the cone cutting tooth bit with the primary and assistant nozzles can directly avoid 85.33% drilling fluid flushing core and reduce the disturbance of drilling fluid to the core samples. The water passage structure of the bit is reasonable, and the upward return velocity of the drilling fluid can be stabilized between 0.7 and 1.8 m/s, which meets the requirements of the upward return of cuttings in seabed strata, and has a good hole wall protection performance. Based on the bottom-jet diamond bit, the assistant nozzles are added. The drilling fluid of the assistant nozzles can better cover the bit crown, conductive to cooling the bit crown. The drilling fluid of the main nozzles can timely up-return along the outer annulus hole wall, conducive to the up-return of the cuttings with drilling fluid. This study can extend existing designs of a seafloor coring bits and bottom hole flow field analysis methods.

Spatio-temporal signature of surface biophysical parameters in response to extreme IOD events using remote sensing

The Indian Ocean (IO) evidenced significant effects on regional and global ocean-atmospheric coupling variability in recent decades. Anomalous negative (positive) Indian Ocean Dipole (IOD) events witnessed along tropical IO during 2016 (2019) are one of them. The spatial signature of anomalous IOD events was studied using sea surface temperature anomaly (SSTA), sea surface height, sea surface salinity, chlorophyll-a, zonal and meridional wind components obtained from remote sensing data. The strong easterly wind anomaly blowing along the Sumatra coast causes strong coastal upwelling pioneer for the positive IOD event in 2019. The westward horizontal advection of seawater leads to low (high) sea surface height anomaly along eastern (western) tropical IO. The eastern (western) tropical IO becomes gradually cold (warm) during the mature phase (September–October–November) of positive IOD. Due to strong upwelling high and low sea surface salinity were observed along the eastern and western tropical IO respectively. The prolonged stronger upward (downward) Ekman pumping velocity in east (west) results in divergence (convergence) of seawater responsible for the increase (decrease) of chlorophyll-a and marine primary productivity. The reverse phenomena were characterized by warmer (cooler) SSTA, higher (lower) sea surface height, low (high) sea surface salinity, and decrease (increase) of chlorophyll-a in the eastern (western) tropical IO in the 2016 negative IOD year. The westward (eastward) zonal Ekman mass transport is possible fueling the extreme condition of positive (negative) IOD events. A strong eastward propagating downwelling Kelvin wave was observed due to the reflection of the upwelling Rossby wave from the African coast. Dominated picoplankton (microplankton) to other phytoplankton size classes are responsible for the reoccurrence of open ocean bloom along western (eastern) tropical IO during positive IOD.

Investigating the Role of Gravity Waves on Equatorial Ionospheric Irregularities Using TIMED/SABER and C/NOFS Satellite Observations

In this paper, for the first time, simultaneous atmospheric temperature perturbation profiles obtained from the TIMED/SABER satellite and equatorial ion density and vertical plasma drift velocity observations with and without ESF activity obtained from the C/NOFS satellite are used to investigate the effect of gravity waves (GW) on ESF. The horizontal and vertical wavelengths of ionospheric oscillations and GWs are estimated by applying wavelet analysis techniques. In addition, vertically propagating GWs that dissipate energy in the ionosphere-thermosphere system are investigated using the spectral analysis technique. We find that the vertical wavelength of GW, corresponding to dominant wavelet power, ranges from 12 to 31 km regardless of the conditions of the ionosphere; however, GWs with vertical wavelengths between about 1 to 13 km are found every day, saturated between 90 and 110 km at different longitudinal sectors. Filtering out vertical wavelengths above 13 km from temperature perturbations, ranges of zonal wavelengths of GW (i.e., from about 290 to 950 km) are found corresponding to irregular and non-irregular ionosphere. Similarly, corresponding to dominant oscillations, the zonal wavelength of ion density perturbations is found within 16 to 1520 km. Moreover, we find an excellent agreement among the median zonal wavelengths of GW for the cases of irregular and non-irregular ionosphere and ion density perturbations that are 518, 495, and 491 km, respectively. The results imply that seed perturbations due to GW with a vertical wavelength from about 1 to 13 km evolve to ion density irregularity and may be amplified due to post-sunset vertical upward drift velocity.

Clean smoldering biowaste process: Effect of burning direction on smoke purification by self-sustained flame

Smoldering is an attractive biowaste removal technology, but its toxic pollutions are significant concerns. This work explores smoldering biowaste removal with the emissions purified by a self-sustained flame and the effect of smoldering direction. The smoldering direction and intensity are controlled by the ignition position and upward internal airflow velocity (5–24 mm/s). We found that the flame can be sustained above the smoldering fronts to purify the smoldering emissions in different burning directions, and the flame duration and burnt mass fraction are much larger for the opposed smoldering. To sustain a flame above an opposed smoldering front, the minimum airflow velocity is 6 mm/s, and the minimum smoldering burning flux is 10 ± 1 g/m2∙s. Comparatively, sustaining a flame above a forward smoldering requires a larger airflow velocity (~11 mm/s) and smoldering intensity (>16 g/m2∙s). Therefore, the flame is easier to remove more emissions from opposed smoldering which is recommended for the waste removal process. The critical smoldering burning flux at flame extinction is constant at 9 ± 1 g/m2∙s, regardless of the smoldering direction and airflow velocity. This work deepens the understanding of the co-existence of smoldering and flaming and enriches strategies for environmentally friendly smoldering waste removal technologies.

The spring–neap variability and mechanisms of long-term variations in the upwelling at the tip of Liaodong Peninsula, China

Upwelling is one of the important phenomena in oceans which plays a significant role in marine hydrology and marine ecological systems. During the summer stratified season, there are usually cold patches around the tip of Peninsula. Using the satellite sea surface temperature (SST) data from 1999 to 2018, this study showed that there was a pod-like cold water patch with two cold centers around the tip of Liaodong Peninsula, China. The range and the intensity of upwelling indicated an increasing trend during 1999–2018. We used a two-dimensional hydrodynamic model Mike21 to study the impact of the tidal current to the intra-month variations of upwelling (DHI 2009). The variability of tidal currents brought the significant spring–neap variations of the upwelling, showing that the SST of upwelling during the spring tide was lower about 1°C and the range of the cold water extended farther than that during the neap tide. The variations of upwelling area lagged behind the tide range about 4 days. The mechanisms of long-term variations of the upwelling were analyzed using the remote sensing wind data and the reanalysis ocean current data. Summer surface wind in the Bohai Sea suppressed the upwelling through the inshore Ekman transports and the effect of the wind curls could be ignored. The dispersion of geostrophic current around the Laotieshan Channel due to the bottom friction could drive the upward vertical velocities. Both of wind and current contributed to the multi-year variations of the upwelling around the tip of Liaodong Peninsula, China.

Hydrodynamic analysis of the energy dissipation of droplets on vibrating superhydrophobic surfaces

In this paper, experimental and numerical methods are presented to describe the hydrodynamic process of the vibration-induced detachment of a droplet from a superhydrophobic surface. We conduct the investigation of the droplet dynamics under various vibration and impact parameters, from an energy conversion perspective. In particular, the energy dissipation that occurs following the droplet impact is analyzed quantitatively. We identify three viewpoints on vibration-induced droplets. Firstly, the phase angle is the dominant factor in characterizing the droplet morphology evolution and energy dissipation on a vibrating surface. The law governing the initial phase angle is affected by the vibration frequency, while the intensity is affected by the vibration amplitude. Secondly, the energy dissipation is positively correlated with the maximum spreading diameter and impact velocity. A larger initial diameter tends to produce a longer contact time. Finally, the central jet formation depends heavily on the upward velocity of the concave liquid, under the peculiar morphology of a vibration-induced droplet. For all these effects, up to 60% of the total energy is squandered during impact, while the surface energy remains almost constant. Much of the droplet's kinetic energy is lost in resisting the viscous force of the substrate.

Three-Dimensional Flow Velocity Estimation of Mountain Glacier Based on SAR Interferometry and Offset-Tracking Technology: A Case of the Urumqi Glacier No.1

Remote sensing estimations of glacier flow velocity could provide effective methods for the long-term monitoring of glacier flow velocity. This paper calculated the velocity in the line-of-sight (LOS) direction by combining DInSAR and offset-tracking technology with ascending and descending Sentinel-1 images of the Urumqi Glacier No.1 from 2016 to 2017. Meanwhile, the velocity in the azimuthal direction was obtained by combining MAI and offset-tracking technology. Then, the eastward, northward, and upward flow velocities were retrieved using the Helmert variance component estimation method. Finally, the standard error of the mean and mean errors of surface velocity in non-glaciated areas of the Urumqi Glacier No.1 were calculated to evaluate the accuracy of the results generated by the proposed method. The results showed: (1) The ascending LOS velocity and the descending LOS velocity were 1.812 m/a and −1.558 m/a from 2016 to 2017. The ascending azimuthal and descending azimuthal velocities were 0.978 m/a and −2.542 m/a, respectively. (2) The glacier flow velocities were 2.571 m/a and 1.801 m/a, respectively, for the eastward and northward directions. In the vertical direction, the velocity was −0.554 m/a. (3) The accuracy of the results generated by the proposed method were 0.028 m/a, 0.085 m/a, and 0.063 m/a in the east, north, and vertical directions. Therefore, it is suitable to use ascending and descending Sentinel-1 images and the study method proposed in this paper to estimate the surface flow velocity of mountain glaciers.

Multi-level continuous monitoring of indoor radon activity

We present the results of an experiment taking place inside the geophysical museum of Rocca di Papa (Rome, Italy), where the high radon levels detected might pose a risk to the health of workers and of the public audience. As a first step towards the mitigation of potential exposure risk, four active sensors were installed at different floors of the building, in order to continuously monitor not only radon exhalation from the soil but also its transport from the ground up to elevated floors. Collecting more than three years of data of radon concentration enables us to identify fluctuations over both short and seasonal scales and to elucidate the relation between radon variations and changes of internal temperature and relative humidity. The analysis of such dataset reveals how the healthiness of indoor environments in terms of radon concentration is controlled by a number of factors, including the environmental conditions and the use of heating and ventilation systems. Finally, the continuous radon monitoring at different levels of the building provides a unique chance to trace the vertical radon diffusion, allowing to make a first-order estimate of upward radon velocity.

The Presence of a Substrate Strengthens The Jet Generated by Upside-Down Jellyfish

Upside-down jellyfish, Cassiopea, are prevalent in warm and shallow parts of the oceans throughout the world. They are unique among jellyfish in that they rest upside down against the substrate and extend their oral arms upwards. This configuration allows them to continually pull water along the substrate, through their oral arms, and up into the water column for feeding, nutrient and gas exchange, and waste removal. Although the hydrodynamics of the pulsation of jellyfish bells has been studied in many contexts, it is not clear how the presence or absence of the substrate alters the bulk flow patterns generated by Cassiopea medusae. In this paper, we use three-dimensional (3D) particle tracking velocimetry and 3D immersed boundary simulations to characterize the flow generated by upside-down jellyfish. In both cases, the oral arms are removed, which allows us to isolate the effect of the substrate. The experimental results are used to validate numerical simulations, and the numerical simulations show that the presence of the substrate enhances the generation of vortices, which in turn augments the upward velocities of the resulting jets. Furthermore, the presence of the substrate creates a flow pattern where the water volume within the bell is ejected with each pulse cycle. These results suggest that the positioning of the upside-down jellyfish such that its bell is pressed against the ocean floor is beneficial for augmenting vertical flow and increasing the volume of water sampled during each pulse.

Generation Mechanisms of Plasma Density Irregularity in the Equatorial Ionosphere During a Geomagnetic Storm on 21–22 December 2014

AbstractThe equatorial ionosphere endured plasma density irregularities during a geomagnetic storm on 21–22 December 2014. To understand the underlying mechanism, we analyzed the rate of the total electron content change (ROTI) data obtained from a global navigation satellite system, along with solar wind, interplanetary magnetic field (IMF), geomagnetic indices, Jicamarca incoherent scatter radar, and magnetometer data. The results indicate that the ROTI enhancement related to plasma density irregularities (plasma bubbles) occurred three times in the equatorial and low latitude regions of the American sector during the geomagnetic storm. The first, second, and third enhancements which have a longitudinal extent of ∼20° appeared in the post‐sunset, pre‐midnight, and post‐midnight sectors, respectively. The second enhancement occurred during the recovery phase of the storm‐time substorm even though the IMF remained southward. During this period, the direction of the dayside equatorial electrojet (EEJ) changed from eastward to westward, while the nightside upward plasma velocity at Jicamarca increased to 28.8 m/s. The response of the EEJ and upward ion drift implies that the westward and eastward electric fields were intensified on the dayside and nightside, respectively. Therefore, these results suggest that an over‐shielding electric field penetrates the dayside/nightside equator simultaneously in association with a substorm recovery phase, and that the electric field generates plasma bubbles by the Rayleigh‐Taylor instability mechanism. Plasma bubbles induced by the penetration of an over‐shielding electric field due to substorm activity have not previously been reported.

Effectiveness and Relationship between Biased and Unbiased Measures of Dopamine Release and Clearance.

Fast-scan cyclic voltammetry (FSCV) is an effective tool for measuring dopamine release and clearance throughout the brain, especially the striatum where dopamine terminals are abundant and signals are heavily regulated by release machinery and the dopamine transporter (DAT). Peak height measurement is perhaps the most common method for measuring dopamine release, but it is influenced by changes in clearance. Michaelis-Menten-based modeling has been a standard in measuring dopamine clearance, but it is problematic in that it requires experimenter fitted modeling subject to experimenter bias. This study presents the use of the first derivative (velocity) of evoked dopamine signals as an alternative approach for measuring and distinguishing dopamine release from clearance. Maximal upward velocity predicts reductions in dopamine peak height due to D2 and GABAB receptor stimulation and by alterations in calcium concentrations. The Michaelis-Menten maximal velocity (Vmax) measure, an approximation for DAT levels, predicts maximal downward velocity in slices and in vivo. Dopamine peak height and upward velocity were similar between wild-type and DAT knock-out (DATKO) mice. In contrast, downward velocity was lower and exponential decay (tau) was higher in DATKO mice, supporting the use of both measures for extreme changes in DAT activity. In slices, the competitive DAT inhibitors cocaine, PTT, and WF23 increased peak height and upward velocity differentially across increasing concentrations, with PTT and cocaine reducing these measures at high concentrations. Downward velocity and tau values decreased and increased respectively across concentrations, with greater potency and efficacy observed with WF23 and PTT. In vivo recordings demonstrated similar effects of WF23, PTT, and cocaine on measures of release and clearance. Tau was a more sensitive measure at low concentrations, supporting its use as a surrogate for the Michaelis-Menten measure of apparent affinity (Km). Together, these results inform on the use of these various measures for dopamine release and clearance.

The controlling mechanisms of horizontal flame spread over thick rods in upward cross flow

This work studies the flame spread over horizontal thick PMMA (polymethyl methacrylate) rods with three radii under different oxygen concentrations and upward cross flow velocities. The flame spread rate and the limit oxygen concentration are measured. Far away from the extinction limit, the flame spread rate increases with the flow velocity but decreases with radius. Near the extinction limit, the flame spread rate is insensitive to the flow velocity and radius. The flame spread rate can be correlated by the stretch rate, and it is found that the flame spread rates for different radii are close at the same stretch rate. A scaling analysis shows that the flame spread rates are approximately square-root dependent on the stretch rate. Prior to the extinction, the flame has entered the regressive burning regime where the flame leading edge will not spread forwardly but continuously retreat. The flame extinction is dependent on the local stretch rate and in-depth heat conduction. For a given radius, the limit oxygen concentration increases with the stretch rate. For a given stretch rate, the smaller cylinder can sustain at lower oxygen concentration due to the less solid-phase heat loss.

Unsteady nanofluid flow between two spinning expanding disks with continuous vertical motion under the influence of modified Hall effect

AbstractThe principle aim of this article is to detect the effects of externally applied magnetic force in the nanofluid flow, flowing between two co‐axially rotating and expanding disks where the upper disk is continuously moving vertically upward and downward. Also, the modified Hall Effect has been considered as an effective factor of the flow. The lower disk is vertically static. The rotation and vertical motion of the disks create a three‐dimensional flow of nanofluid. Heat and mass density along with the motion of the flow has been analyzed under the variation in magnetic and Hall parameters. The findings have been compared with the results in Von Karman flow of nanofluid between two rotating and stretching disks. The velocity components have been largely influenced by magnetic and Hall parameters in case of downward movement of the upper disk. The fluid temperature is detected higher in case of upward velocity and lower in case of the downward motion of the upper disk. The heat transferability of the disks is effected differently at two different disks with the influence of magnetic force and Hall effect.

CFD-DPTM-VOF numerical simulation of particle motion and entrainment under the action of single and double bubbles

In this paper, the three-phase flow, particle motion and entrainment process under the action of single and double bubbles were simulated through the use of computational fluid dynamics-deterministic particle track model-volume of fluid (CFD-DPTM-VOF). First, the physical model was established and the gas-liquid was regarded as a continuous phase. The gas-liquid flow was modeled as turbulent, described by the RNG k-ε model. The volume of fluid (VOF) was used for establishing the gas-liquid interface. Particles were regarded as a discrete phase. DPTM were used for tracking particle motion. Second, the simulation results were compared with the experimental results based on the analysis of grid independence. The simulation results were in good agreement with the experimental results. Third, the influence of bubble motion on particle distribution and entrainment was revealed through simulation and analysis. The entrainment law of 10, 50, 100, and 500 μm particles were described qualitatively and quantitatively. Numerical results showed that the vortex region formed by the rising bubbles had a notable entrainment effect on the 10, 50, and 100 μm particles, which caused the bottom of the bubbles to form upward velocity. The 10 μm particles were mostly suspended in the liquid pool, while the 500 μm particles were mostly unaffected by bubble entrainment and mainly concentrated at the bottom of the liquid pool. In addition, the height of entrainment and number of entrainment particles decreased as particle size increased under the action of single and double bubbles. Our findings indicate that, compared with single bubble, double bubbles have two entrainment processes, and particles can be carried to a higher height with an increased number of entrained particles at the same time. The work lays a foundation for further explorations on the gas-liquid-solid flows and possible industry applications.