Plume Behavior Research Articles

Thyroid equivalent doses for evacuees and radiological impact from the Fukushima nuclear accident

The present paper summarizes the scientific activities of the authors which have been focused on environmental monitoring and estimating thyroid dose for evacuees of the Fukushima Nuclear Power Plant accident. The radionuclide components of the absorbed dose rates in air obtained by a gamma-ray spectrometer depend on the radioactive plume behavior. Furthermore, continuous measurements by a car-borne survey are important to know the radioactive plume behavior. A few thyroid dose estimations have been obtained by different techniques. Direct measurements by the authors were in agreement with these published estimations. However, the dose from 132I was not taken into account in the previously published thyroid dose estimation due to the lack of information. After a nuclear accident, prompt thyroid measurements are required, and a standard technique for the measurement of activity in thyroid should be established.

Buoyancy driven turbulent plume induced by protruding heat source in vented enclosure

The buoyancy driven thermal plume behavior inside a partial square enclosure with protruding isothermal heat source block is numerically investigated. The turbulent flow is modeled by using unsteady Favre-averaged Navier-Stokes (UFANS) equation with buoyancy modified Lam Bremhorst low Reynolds number k−ϵ model. A Simplified Marker and Cell algorithm (SMAC) is used to solve the governing equations and the computations are performed using an in-house code based on Finite difference method. The heat transfer characteristics and the bidirectional exchange across the vent are analyzed for different Grashof number 108 ≤ Gr ≤ 1011. Further, the thermal plume patterns are investigated by mounting the heat source block at five different locations δ = 0.25 H, 0.35 H, 0.5 H, 0.65 H and 0.75 H. A significant enhancement in the net mass flow rate and average Nusselt number is observed by increasing the Grashof number. It is found that the heat source location has strong influence on the vent bidirectional exchange rate, thermal mixing and heat transfer characteristics inside the enclosure. The present model is validated with the experimental and numerical benchmark results available in literature.

Effects of mesoscale eddies on behavior of an oil spill resulting from an accidental deepwater blowout in the Black Sea: an assessment of the environmental impacts.

Because of the environmental sensitivity of the Black Sea, as a semi-enclosed sea, any subsea oil spill can cause destructive impacts on the marine environment and beaches. Employing numerical modeling as a prediction tool is one of the most efficient methods to understand oil spill behavior under various environmental forces. In this regard, a coupled circulation/deepsea oil spill model has been applied to the Black Sea to address the behavior of the oil plume resulting from a representative hypothetical deepwater blowout. With climatological forcing, the hydrodynamic module based on DieCAST ocean circulation model realistically reproduces seasonally-varying circulation from basin-scale dominant structures to meso- and sub-mesoscale elements. The oil spill model utilizes pre-calculated DieCAST thermo-hydrodynamic fields and uses a Lagrangian tracking algorithm for predicting the displacement of a large number of seeded oil droplets, the sum of which forms the rising oil plume resulting from a deepwater blowout. Basic processes affecting the transport, dispersal of oil and its fate in the water column are included in the coupled model. A hypothetical oil source was set at the bottom, at the northwestern edge of the Shatsky Ridge in the area east of the Crimea Peninsula where the oil exploration/development is likely to be planned. Goals of the study are to elucidate the behavior of the subsea oil plume and assess scales of contamination of marine environment and coastlines resulting from potential blowouts. The two 20-day scenarios with the oil released by a hypothetical blowout were examined to reveal combined effects of the basin-scale current, near-shore eddies, and winds on the behavior of the rising oil plume and its spreading on the surface. Special attention is paid to the Caucasian near-shore anticyclonic eddy which is able to trap surfacing oil, detain it and deliver it to shores. The length of contaminated coastlines of vulnerable Crimean and Caucasian coasts are assessed along with amounts of oil beached and deposited.

Simulation and assessment of underwater gas release and dispersion from subsea gas pipelines leak

Abstract Subsea gas release and dispersion can cause safety concerns such as fire, explosion or stability loss of floating installations. This paper presents a Computational Fluid Dynamics (CFD) based approach to describe the behavior of underwater gas release and dispersion from subsea gas pipelines leak. The uniqueness of the present study is the integration of estimating subsea gas release rate and predicting rising gas plume. The proposed approach is comprised of two submodels. An equivalent short pipeline model is established to calculate the subsea gas release rate, considering the change of hole size and environmental pressure. A 3D model based on Eulerian-Lagrangian modeling concept is built to predict the rising gas plume, in which bubbles are treated as discrete particles. The validation is carried out by comparing CFD results against experimental data. The underwater gas dispersion simulations include a matrix of scenarios for different gas release rates, water depths, ocean current speeds and leak positions, to study their effects on the behavior of underwater gas plume. The developed CFD model can provide some valuable outputs, e.g., gas release rate, rise time, horizontal dispersion distance and surfacing area size. These results could help to conduct the risk assessment and the emergency planning for accidental leakage of subsea gas pipelines.

The Role of Capillary Hysteresis and Pore‐Scale Heterogeneity in Limiting the Migration of Buoyant Immiscible Fluids in Porous Media

AbstractUnderstanding the main mechanisms affecting long‐term migration and redistribution of injected CO2 in geological carbon storage is needed for developing predictive models to assess environmental risks and designing monitoring schemes. Preparation of a postinjection site care plan is required for CO2 injection wells, including monitoring of pressure changes and injected CO2 plume. Knowledge gaps exist regarding assessment of postinjection monitoring timeframes for the CO2 plume because the processes driving long‐term CO2 plume migration and trapping are not fully understood. In the postinjection stage of geological carbon storage, redistribution of CO2 occurs mainly due to buoyancy and capillary forces. This work presents experimental and modeling studies to investigate processes contributing to postinjection plume distribution and stabilization. We conducted a flow cell experiments (0.5 m × 0.05 m × 0.01 m) with two immiscible fluid phases in a glass bead porous medium to study postinjection plume behavior. We employed a hysteretic macroscopic two‐phase flow model to interpret the experimental results and to understand main processes leading to plume stabilization. Our findings show that capillary pressure hysteresis explains the experimentally observed plume shape and redistribution at early postinjection stages; however, the long‐term plume migration and eventual plume stabilization can only be represented when in addition microscale heterogeneity is accounted for. Results also show that plume stabilization can be extremely slow and that the migration of the plume front can occur through multiple intermittent bursts over long times. Further studies are needed to understand implications of the results for more realistic porous media and large‐scale storage reservoirs.

A Laboratory Study of Iceberg Side Melting in Vertically Sheared Flows

AbstractAn earlier study indicates that the side melting of icebergs subject to vertically homogeneous horizontal velocities is controlled by two distinct regimes, which depend on the melt plume behavior and produce a nonlinear dependence of side melt rate on velocity. Here, we extend this study to consider ice blocks melting in a two-layer vertically sheared flow in a laboratory setting. It is found that the use of the vertically averaged flow speed in current melt parameterizations gives an underestimate of the submarine side melt rate, in part because of the nonlinearity of the dependence of the side melt rate on flow speed but also because vertical shear in the horizontal velocity profile fundamentally changes the flow splitting around the ice block and consequently the velocity felt by the ice surface. An observational record of 90 icebergs in a Greenland fjord suggests that this effect could produce an average underestimate of iceberg side melt rates of 21%.

Characteristics of chiral plasma plumes generated in the absence of external magnetic field

A chiral plasma plume has recently been generated inside a dielectric tube without the use of an external magnetic field. In this paper, we seek to further study the key properties of such a chiral plume to improve our understanding of how this interesting structure is generated and controlled. The chiral plume is generated by externally mounting a stainless steel helical coil or a ring onto the dielectric tube. By changing the pitch of the helical coil, the pitch of the plasma plume can be controlled, with the shape of the plume following the shape of the helical coil. The addition of the helical coil significantly expands the range of parameters under which the chiral plasma plume appears. When the frequency of the applied voltage increases, additional stable discharge channels appear between the adjacent helices. The addition of two helical coils results in the formation of two chiral plasma plumes, which follow the shape of the helical coils. When a metal ring is placed on the outside of the tube, there is no chiral plasma plume between the high voltage electrode and the ring; however, a chiral plasma plume appears on the right side of the ring if the distance between the ring and the high voltage electrode is small. These findings suggest that the chiral plasma can be effectively modulated and guided using an externally mounted helical coil, which acts as the floating/actual ground to reduce the impedance of the discharge and as such contributes to the emergence of the chiral plasma plume behavior.

A Practical Modeling Framework for Non-Fickian Transport and Multi-Species Sequential First-Order Reaction.

Many studies indicate that small-scale heterogeneity and/or mobile-immobile mass exchange produce transient non-Fickian plume behavior that is not well captured by the use of the standard, deterministic advection-dispersion equation (ADE). An extended ADE modeling framework is presented here that is based on continuous time random walk theory. It can be used to characterize non-Fickian transport coupled with simultaneous sequential first-order reactions (e.g., biodegradation or radioactive decay) for multiple degrading contaminants such as chlorinated solvents, royal demolition explosive, pesticides, and radionuclides. To demonstrate this modeling framework, new transient analytical solutions are derived and are inverted in Laplace space. Closed-form, steady-state, multi-species analytical solutions are also derived for non-Fickian transport in highly heterogeneous aquifers with linear sorption-desorption and matrix diffusion for use in spreadsheets. The solutions are general enough to allow different degradation rates for the mobile and immobile zones. The transient solutions for multi-species transport are applied to examine the effects of source remediation on the natural attenuation of downgradient plumes of both parent and degradation products in highly heterogeneous aquifers. Results for representative settings show that the use of the standard, deterministic ADE can over-estimate cleanup rates and under-predict the cleanup timeframe in comparison to the extended ADE analytical model. The modeling framework and calculations introduced here are also applied for a 30 year groundwater cleanup program at a site in Palm Bay, Florida. The simulated plume concentrations using the extended ADE exhibited agreement with observed long concentration tails of trichloroethene, cis 1,2 DCE, and VC that remained above cleanup goals.

Behaviors of Bubble-Entrained Plumes in Air-Injection Artificial Upwelling

AbstractThis paper studies bubble-entrained plume (BEP) behaviors in a crossflow and proposes a theoretical approach for predicting BEP trajectories and the separation points from the bubble swarm....

Numerical simulation of natural convection in a horizontal enclosure: Part I. On the effect of adiabatic obstacle in middle

In this study, an effect of a three-dimensional obstacle of natural convection in a horizontal enclosure was discussed. Geometry which was taken into account was horizontal enclosure with unit aspect ratio and length of π along spanwise direction. The enclosure was heated from the bottom wall, and then was cooled down from above. An obstacle was located in the middle of the enclosure to examine its effect. A three-dimensional solution was obtained using Chebyshev spectral multi-domain methodology for different Rayleigh number at which the thermal behavior was evolved from a steady state to a chaotic pattern. As the geometry was elongated in conjunction with periodic boundary conditions to allow lateral freedom for the convection cells, longitudinal geometry along spanwise direction was discretized through a Fourier series expansion with a uniform mesh configuration. An adiabatic obstacle played a different role in determining the thermal behavior: No-slip condition of the surface of the obstacle disturbed the overall plume behavior in terms of the momentum transfer, whereas the adiabatic boundary condition did not influence significantly in terms of energy transfer. At a low Rayleigh number, thermal behavior in three-dimensional enclosure showed steady invariant solution along spanwise direction which is identical to two-dimensional result. With increasing buoyant force, spanwise invariance of longitudinal roll cell was collapsed and three-dimensional mode was obtained following flow regime transition. After undergoing periodically oscillatory phase, a chaotic flow transition occurred. At a high Rayleigh number, three-dimensional thermal plume oscillates freely in elongated geometry and consequently yields higher heat transfer rate. In addition, the thermal flow field was captured by visualizing the three-dimensional vortical structure. The chaotic three-dimensional flow behavior was quantitatively examined by obtaining the turbulent statistics.

The Implications of Oil Exploration off the Gulf Coast of Florida

In the United States (U.S.), oil exploration and production remain critical economic engines for local, state, and federal economies. Recently, the U.S. Department of the Interior expressed interest in expanding offshore oil production by making available lease areas in the U.S. Gulf of Mexico, the U.S. West Coast and East Coast, as well as offshore Alaska. With the promise of aiding in energy independence, these new lease areas could help solidify the U.S. as one of the world’s largest oil-producing countries, while at the same time bolstering the local and regional energy job sectors. Of all the newly proposed lease areas, the Gulf Coast of Florida is particularly contentious. Opponents of drilling in the area cite the sensitive ecosystems and the local and state tourism economy that depends heavily on the numerous beaches lining Florida’s coast. In this analysis, we use a data-driven spatial analytic approach combined with advanced oil spill modeling to determine the potential impact of oil exploration off of Florida’s Gulf Coast given a loss-of-control event. It is determined that plume behavior varies drastically depending on the location of the spill but that overall impacts are comparable across all spill scenario sites, highlighting the necessity of contingency-type analyses. Implications for spill response are also discussed.

Motion of a Spherical Particle in Microbubble Plume and Bubble Behavior around the Particle

Motion of a Spherical Particle in Microbubble Plume and Bubble Behavior around the Particle

Falling of a Spherical Particle in Microbubble Plume and Microbubble Behavior around the Particle

Falling of a Spherical Particle in Microbubble Plume and Microbubble Behavior around the Particle

CO2 Leakage-Induced Contamination in Shallow Potable Aquifer and Associated Health Risk Assessment

Leakage of stored CO2 from a designated deep reservoir could contaminate overlying shallow potable aquifers by dissolution of arsenic-bearing minerals. To elucidate CO2 leakage-induced arsenic contamination, 2D multispecies reactive transport models were developed and CO2 leakage processes were simulated in the shallow groundwater aquifer. Throughout a series of numerical simulations, it was revealed that the movement of leaked CO2 was primarily governed by local flow fields within the shallow potable aquifer. The induced low-pH plume caused dissolution of aquifer minerals and sequentially increased permeabilities of the aquifer; in particular, the most drastic increase in permeability appeared at the rear margin of CO2 plume where two different types of groundwater mixed. The distribution of total arsenic (∑As) plume was similar to the one for the arsenopyrite dissolution. The breakthrough curve of ∑As monitored at the municipal well was utilized to quantify the human health risk. In addition, sensitivity studies were conducted with different sorption rates of arsenic species, CO2 leakage rates, and horizontal permeability in the aquifer. In conclusion, the human health risk was influenced by the shape of ∑As plume, which was, in turn, affected by the characteristics of CO2 plume behavior such as horizontal permeability and CO2 leakage rate.

Chaotic behavior of human thermal plumes in an aircraft cabin mockup

The human thermal plume induced by body heat loss has a significantly impact on human thermal comfort, contaminant transport and indoor air quality. Few studies focused on the temporal unsteady characteristics of human thermal plume. In this study, the human thermal plume generated by a heated manikin was measured in a 7-row cabin mockup by mini particle image velocimetry (mini-PIV) system; and its unsteady and chaotic behavior was determined out of statistical and chaotic method. Probability density distributions of velocity time series of human thermal plumes presented Gaussian mixture models with two peaks, which substantiated the oscillating characteristics of human thermal plumes. The energy region of the human thermal plume was concentrated between 0.1 Hz and 10 Hz determined out of the power spectrum analysis, and the power spectrum exponent of the human thermal plume above the head ranged from 0.9 to 1.2. Evolution of phase space reconstruction of velocity time series from single-spindle to double-spindle revealed the human thermal plume presents obvious autocorrelation and oscillating behavior qualitatively. In addition, the fractal dimension of human thermal plumes overhead ranged from 6 and 12 without integers and Kolmogorov entropies of analyzed points were all larger than zero indicating the human thermal plume was kind chaotic airflow quantitatively.

Simulation of river plume behaviors in a tropical region: Case study of the Upper Gulf of Thailand

River plumes are a general phenomenon in coastal regions. Most previous studies focus on river plumes in middle and high latitudes with few studies examining those in low latitude regions. Here, we apply a numerical model to the Upper Gulf of Thailand (UGoT) to examine a river plume in low latitudes. Consistent with observational data, the modeled plume has seasonal variation dependent on monsoon conditions. During southwesterly monsoons, the plume extends northeastward to the head of the gulf; during northeasterly monsoons, it extends southwestward to the mouth of the gulf. To examine the effects of latitude, wind and river discharge on the river plume, we designed several numerical experiments. Using a middle latitude for the UGoT, the bulge close to the river mouth becomes smaller, the downstream current flows closer to the coast, and the salinity in the northern UGoT becomes lower. The reduction in the size of the bulge is consistent with the relationship between the offshore distance of a bulge and the Coriolis parameter. Momentum balance of the coastal current is maintained by advection, the Coriolis force, pressure gradient and internal stresses in both low and middle latitudes, with the Coriolis force and pressure gradient enlarged in the middle latitude. The larger pressure gradient in the middle latitude is induced by more offshore freshwater flowing with the coastal current, which induces lower salinity. The influence of wind on the river plume not only has the advection effects of changing the surface current direction and increasing the surface current speed, but also decreases the current speed due to enhanced vertical mixing. Changes in river discharge influence stratification in the UGoT but have little effect on the behavior of the river plume.

Influence of hydrodynamic behavior of laser ablation plume on cluster formation

We conducted fast-photography of the ablation plume and mass analysis of generated clusters. Time-resolved observation of the ablation plumes showed that the behavior of the plume drastically changes depending on the background helium gas pressure. Particularly when the pressure was more than 100 Pa, a strong light emission from the front edge of the plume was observed, indicating that the strong compression of the plume vapor occurs and the kinetic energy of the drifting plume may be converted into the thermal energy of the compressed vapor. We found that this plume compression process could be enhanced by introducing an ellipsoidal cavity, which is due probably to converging waves in the background gas towards the focal point of the ellipsoid. A TOF mass spectroscopy indicated that clusters having a mass corresponding to Al, AlO, Al2, and Al2O were generated in the laser ablation cavity and transported downstream. However, large aluminum clusters consisting of more than a few tens of atoms were not observed in the present experimental condition.

Physical and mathematical modeling of bubbles plume behaviour in one strand tundish

Moving through the liquid steel, argon bubbles intensify the chemical and thermal homogenisation processes and liquid metal refining. The present study reports the physical and mathematical modeling of bubbles behaviour in the tundish with argon injection system. The 210 litre–capacity one strand slab tundish model was made on a scale of 2:5. The laboratory water model experiments have demonstrated that the identical porous material used in gas-permeable barrier may generate gas bubbles varying in size and shape. This fact will also affect both vertical and horizontal velocities attained by the bubbles. From numerical simulations influence of argon flow rate on liquid steel velocity for free surface in the tundish was obtained. The results from numerical simulations indicate that argon create increasing of liquid steel velocity and vortex structures.

Opto-Electron Eng, 2017, 44(10)] Research status and development prospects of laser welding under vacuum

Compared with conventional laser welding, the welding quality was improved significantly while the laser welding was conducted under vacuum. The penetration depth of the weld seam increased sharply. The welding formation was improved and the porosity defects were suppressed effectively. In recent years, numerous researches on the mechanism of welding process, low vacuum and local subatmospheric pressure laser welding equipments have been undertaken. The laser welding under vacuum exhibits the wonderful application prospects to weld the thick plates in the shipbuilding, nuclear instrument and pressure vessel industries. The influences of ambient pressure on the laser welding penetration depth, surface formation and porosity defect were summarized. The domestic and overseas research findings on mechanism of laser welding under vacuum were elaborated from the aspects of plasma plume, keyhole and molten pool behaviors. In addition, the applications of laser welding under vacuum in the industry were introduced. Finally, the problems of reported researches were analyzed and the prospects of the technology were discussed.

On the evolution of the plume function and entrainment in the near-source region of lazy plumes

Plumes occur in many natural and industrial settings, such as chimney smoke, volcanic eruptions and deep water oil spills. A plume function, $\unicode[STIX]{x1D6E4}$, is used to characterize plumes and jets. The far-field behaviour of these flows has been studied in great detail while the near-field behaviour has not quite received the same attention. We examine near-field phenomena such as radial constriction, termed necking, and vortex structure formations with new high resolution direct numerical simulations. Four lazy plumes with increasing values of the source plume parameter, $\unicode[STIX]{x1D6E4}_{0}$, are simulated. We study the evolution of entrainment and the plume function. The original assumptions, that Reynolds stresses dominate viscous shear stresses, do not hold for lazy plumes in the near field. Due to this, a deviation from self-similarity occurs initially and is corrected by a large entrainment coefficient caused by vortex stretching and compression. After correcting for the virtual origin, comparison between theory and simulations shows a monotonic decay of $\unicode[STIX]{x1D6E4}$ towards pure plume behaviour. The entrainment coefficient asymptotes to a widely accepted constant value for plumes.