Plume Behavior Research Articles

Modelling of Plasma Temperatures and Densities in Laser Ablation Plumes of Different Metals

Laser ablation has many uses in industry, including laser drilling and thin-film deposition. However, the underpinning physics of laser ablation has not been fully elucidated. In particular, the differences in the behaviour of plasma plumes ablated from different materials, and which material properties are related to plume characteristics, require further study. This paper presents results from modelling the laser ablation of different photocatalytic materials using the 2D hydrodynamic laser ablation code POLLUX. The evolution of key parameters such as plasma density and temperature is investigated when the target material is changed from titanium to tantalum, zinc, copper, aluminium and gold. It was found that the atomic number of the material significantly affected the electron temperature and mass density of the subsequent plasma plume, with both parameters increasing with atomic number, whilst other parameters including the mass density, thermal conductivity and melting temperature did not affect the electron temperature or particle density of the plumes. These results provide insights for future laser ablation experiments where the aim is to change the target material, but keep the plume parameters as constant as possible.

Analysis of dynamic characteristics of vapor plume of oscillating laser welding of SUS301L-HT stainless steel

Investigations had made much efforts on the vapor plume dynamic characteristics of laser beam welding (LBW) but only showed a little knowledge about the oscillating laser beam welding (OLBW). The velocity magnitude and direction of OLBW varied abidingly, resulting in complicated evolution process of vapor plume. Present research attempted to elucidate the effect of oscillation frequency on the dynamic behavior of vapor plume. The vapor plume morphology was uniform at 50 Hz and 100 Hz. The abrupt change in velocity direction easily led to the occurrence of attenuation and even annihilation of the vapor plume at the frequency less than 20 Hz or greater than 150 Hz. The vapor plume area less than 31.44 mm2 or the vapor plume orientation greater than −40° could be used as the judgment criterion of keyhole instability. The coefficient of variation of vapor plume area or orientation and the proportion of keyhole instability time showed similar trends of first decreasing and then increasing with the increase of oscillation frequency. The stability of vapor plume or keyhole was the best at 50 Hz.

LEACHATE TRANSPORT PHENOMENON ON GROUNDWATER QUALITY: MODELING USING MODFLOW AND MT3DMS TOOLS

<p>The dumping of solid waste in uncontrolled landfills can cause significant impacts on the environment and human health. The open dumps cause the formation of leachate which contaminated the groundwater; use of these groundwater reported danger to the human health. The goal of groundwater protection is necessary to control the release and migration of pollutants from the leachate in the subsurface. In this paper, the above-mentioned problems were dealt with the case study of Ariyamangalam open dumping site, Tiruchirappalli, Tamilnadu. The dump site receives 71% of organic waste. The groundwater flow and leachate transport model was developed using Visual MODFLOW and MT3DMS (Version 4.3), to study the leachate transport in the subsurface and to predict the plume behavior under different scenarios. The conceptual model of the system was derived from the information on geology, geo physical and geo hydrology of the study area. The total dissolved solids (TDS) were taken as a parameter, to study the extent of contaminant plume for the next nine years (2014-2022). From the groundwater flow model, it was found that the increase in water level by 2.5 m above MSL from December 2010 (70.9 m above MSL) to December 2022 (73.4 m above MSL) around the study area. From the leachate transport model, the predicted TDS plume movement was identified towards the west and south east directions of the open dumping area. As a conclusion, the developed groundwater flow and leachate transport model can be effectively used for studying the leachate migration from the open dumping site into subsurface system.</p>

Investigation on the maximum ceiling temperature of the weak plume impingement flow in tunnel fires under longitudinal ventilation

This paper numerically investigated the characteristics of the fire plume behavior and the ceiling maximum temperature with increasing fire source height, in the longitudinal ventilated tunnel fires. Results show that with the continued increase of the longitudinal velocity, the fire plume gradually tilts to the downstream of the tunnel, causing significantly decrease of the ceiling temperature. With the elevation of the fire source, a circulation area forms at the leeward side of the fire source, the pulling effect of the circulation area and the accumulated smoke layer can protect the fire plume from the effect of ventilation airflow, which can weaken the fire plume inclination. To quantify the influence of the longitudinal flow, the dimensionless velocity v* is adopted and divided into three regions, i.e., v*= 0, 0 < v*≤ 0.19 and v*> 0.19. When 0 < v*≤ 0.19, a velocity influence factor f (v) is added to the original equation to represent the effect of ventilation velocity for increasing fire source locations and the ceiling maximum excess temperature varies as the 2/3 power of the dimensionless heat release rate and linear function of dimensionless ventilation velocity. When v* > 0.19, a concept of virtual fire source is proposed to quantify the effects of the inclined fire plume on the maximum temperature and the ceiling maximum excess temperature varies as the 2/3 power of the dimensionless heat release rate and exponential function of dimensionless ventilation velocity. Besides, the applicability and reliability of the predictive correlations are further verified by comparing to the experimental data of different scales.

Electrical characteristics of a Hall effect thruster body in a vacuum facility testing environment

The operational characteristics of Hall effect thrusters are altered by conductive surfaces in vacuum facilities. Conductive surfaces alter charge distribution in the plume by providing pathways for electron-ion recombination that do not exist in the spaceflight environment. Charge recombination pathways impact thruster performance and plume behavior through mechanisms that are not entirely understood. The incomplete understanding of the relationship between charge recombination pathways and thruster behavior limits the ability to characterize thruster performance through ground testing. This paper quantifies the effect of polarity and magnitude of body-to-cathode voltage on coupling between the thruster body and the local plasma environment. The effort operates the T-140 Hall thruster at a single, fixed operating condition of 300 V, 3.5 kW, with anode and cathode xenon flow rates of 11.6 ± 0.03 mg/s and 1.61 ± 0.12 mg/s, respectively. During data collection, the chamber was maintained at a pressure of 8.7 × 10–6 Torr-Xe. The thruster body-to-ground voltage is manipulated by varying body-to-ground resistance. Results show the thruster pole face and body circumference couple to the local plasma environment through distinct sheaths. The polarity of the body-to-cathode voltage determines the characteristics of these sheaths. Therefore, the body-to-cathode voltage controls the interaction between the thruster body recombination pathway and the local plasma environment.

Mixing mechanisms at the strongly-stratified Magdalena River's estuary and plume

This study analyzed the hydrodynamic structure of the estuary and plume of a large, tropical, and strongly-stratified river, the Magdalena. The Magdalena River is the largest source of fresh water and sediment of the Caribbean Sea and drastically impacts the morphodynamics and ecosystems along the Colombian coast. The analyses are based on the results of a calibrated and validated numerical model. Three scenarios of low, mid, and high freshwater discharge were analyzed to consider the seasonal variability of the mixing processes. The relative importance of three mixing mechanisms in the system is investigated, and the estuary and plume are subdivided into sectors depending on the dominant hydrodynamic processes at each sector. The results show that mixing in this system is mainly controlled by turbulence at the pycnocline, especially at the lift-off point in the transition between the estuary and the plume's near-field. A hydraulic jump occurs in the transition between the near- and mid-fields of the plume, but the mixing produced here is comparatively low since the plume has been mostly diluted already in the estuary and the near-field. During low and mid discharge scenarios, saline intrusion in the river channel forms a strongly stratified estuary where bottom propagated turbulence generates instabilities producing minor mixing. Meanwhile, the saltwater is flushed out of the river during the high discharge scenario, and pycnocline instabilities produce mixing at least one order of magnitude larger than during low discharge conditions. Coriolis acceleration does not seem to be a relevant driver of the plume behavior, despite the larger extension of the plume during high discharges, given the low latitude of the system.

Applying a big data analysis to evaluate the suitability of shelter locations for the evacuation of residents in case of radiological emergencies

During a nuclear power plant (NPP) accident, radioactive material may be released into the surrounding environment in the form of a radioactive plume. The behavior of the radioactive plume is influenced by meteorological factors such as wind direction and speed. If the residents are evacuated to a shelter in the direction of the flow of the radioactive plume, the radiation exposure of the residents may increase, contrary to the purpose of the evacuation. To avoid such an undesirable outcome, this paper applies a big data analysis to evaluate the suitability of the shelter locations near 5 NPPs in the Republic of Korea in terms of the seasonal wind direction frequency in those areas. To this end, the wind data measured around the NPPs from 2016 to 2020 were analyzed to derive the seasonal wind direction frequency using a big data analysis. These analyses results were then used to determine how many shelters around NPPs locate in areas with prevailing wind direction per season. Then, suggestions were made on the direction for residents not to evacuate, if possible, that is, the prevailing seasonal wind directions for 5 NPPs, depending on the season in which the accident occurs.

Systematic shift in plume bending direction at Grotto Vent, Main Endeavour Field, Juan de Fuca Ridge implies changes in venting output along the Endeavour Segment

Analysis of the time-dependent behavior of the buoyant plume rising above Grotto Vent (Main Endeavour Field, Juan de Fuca Ridge) as imaged by the Cabled Observatory Vent Imaging Sonar (COVIS) between September 2010 and October of 2015 captures long term time-dependent changes in the direction of background bottom currents independent of broader oceanographic processes, indicating a systematic evolution in vent output along the Endeavour Segment of the Juan de Fuca Ridge. The behavior of buoyant plumes can be quantified by describing the volume, velocity, and orientation of the effluent relative to the seafloor, which are a convolved expression of hydrothermal flux from the seafloor and ocean bottom currents in the vicinity of the hydrothermal vent. We looked at the azimuth and inclination of the Grotto plume, which was captured in three-dimensional acoustic images by the COVIS system, at 3-h intervals during October 2010 and between October 2011 and December 2014. The distribution of plume azimuths shifts from bimodal NW and SW to SE in 2010, 2011, and 2012 to single mode NW in 2013 and 2014. Modeling of the distribution of azimuths for each year with a bimodal Gaussian indicates that the prominence of southward bottom currents decreased systematically between 2010 and 2014. Spectral analysis of the azimuthal data showed a strong semi-diurnal peak, a weak or missing diurnal peak, and some energy in the sub-inertial and weather bands. This suggests the dominant current generating processes are either not periodic (such as the entrainment fields generated by the hydrothermal plumes themselves) or are related to tidal processes. This prompted an investigation into the broader oceanographic current patterns. The surface wind patterns in buoy data at two sites in the Northeast Pacific and the incidence of sea-surface height changes related to mesoscale eddies show little systematic change over this time-period. The limited bottom current data for the Main Endeavour Field and other parts of the Endeavour Segment neither confirm nor refute our observation of a change in the bottom currents. We hypothesize that changes in venting either within the Main Endeavour Field or along the Endeavour Segment have resulted in the changes in background currents. Previous numerical simulations (Thomson et al., J. Geophys. Res., 2009, 114 (C9), C09020) showed that background bottom currents were more likely to be controlled by the local (segment-scale) venting than by outside ocean circulation or atmospheric patterns.

Coupling Warm Rain With an Eddy Diffusivity/Mass Flux Parameterization: 2. Sensitivities and Comparison to Observations

AbstractThis is the second part of the description and validation of the coupling of a warm‐rain microphysics scheme to a stochastic multi‐plume eddy‐diffusivity/mass‐flux parameterization. Part 1 provides the model description and initial validation of the parameterization in a single column model (SCM) against large eddy simulations. This manuscript provides additional comparisons against satellite observations of 500 unique simulation cases, an analysis of model parameter‐based sensitivities in those 500 cases, and an evaluation of the idealized LES case study paradigm for parameterization development. The SCM is forced by a weather reanalysis in the subtropical northeast Pacific region characterized by the stratocumulus‐to‐cumulus cloud transition. 18 scalar outputs are examined to identify the sensitivities to 22 of the model's parameters. The model is highly sensitive to parameters that determine the behavior of convective plumes, which collectively lead to the most sensitivity in 13 of the 18 outputs. Only a few parameters contribute sensitivities that are not highly correlated with those of other parameters. While forcing the model with two canonical field campaign cases results in similar picture of which parameters lead to high sensitivity in model outputs, the sensitivity magnitudes can be overestimated compared to when the model is forced by weather reanalyzes.

Numerical study of electric plume in viscoelastic fluids within a blade-plate structure

A two-dimensional numerical study on the behavior of electric plumes in viscoelastic fluids within a blade-plate structure is conducted herein. The Oldroyd-B constitutive equation is used to model the viscoelastic fluid. The effects of elasticity on the development processes of electric plumes and the heat transfer characteristics are mainly investigated. Moreover, the flow structure of the electric plume with self-similar characteristics which is similar to the thermal plume has been successfully characterized using the evolution of the charge distribution. Additionally, the results show that the elastic effect can promote electric plume development. The stronger the elastic effect is, the faster the electric plume rises. Furthermore, the influence of other dimensionless parameters on the electric plume is analyzed. When considering the impingement cooling effect of the electric plume, the elastic effect inhibits the heat transfer of the system after the plume fully develops.

Impact of the lower Jurassic Dunlin Group depositional elements on the Aurora CO2 storage site, EL001, northern North Sea, Norway

Northern Lights is the CO2 transport and storage component of Longship, the Norwegian full-scale CCS project. Injection is planned into an under-explored sloping saline aquifer in the northern North Sea, the Johansen and Cook formations of the Lower Jurassic Dunlin Group. To bridge the information gap, well 31/5-7 (Eos) was drilled. The comprehensive dataset acquired was fundamental to interpret the depositional environment and determine the scale and spatial distribution of heterogeneities, as input to 3-D models aimed at improving storage resource assessment and understanding the injected CO2 plume behaviour over time. The interpreted gross depositional environments of the storage units are marginal- to shallow-marine, arranged in three successive fining-upwards intervals. The lower interval includes coastal deposits with mixed wave- and river influence, correlatable over a large distance, dominated by meso-scale heterogeneities. The middle interval records paralic deposits with a wave- and tidal- interplay generating higher vertical and lateral variability. The upper interval is interpreted as tidal-dominated, predominantly with cm-scale heterogeneities. The repeated fining-upwards trends are ideal for plume redistribution and efficient CO2 storage, and the reconstructed lateral depositional trends associated with generally good properties indicate a high storage potential. The Eos well data enabled building the properties distribution model, highlighting the importance of well control for storage evaluation.

Investigation on Effect of Ceiling Vent Location on Fire Phenomena in Enclosure with Side and Ceiling Vents

In this study, the effect of ceiling vent location on the fire phenomena in the enclosure with side and ceiling vents was numerically investigated. As the ceiling vent location, Case F, Case F-M, Case M, Case M-B, and Case B were tested, and their distances from the side vent to the center of each vent were 0.265, 0.525, 0.750, 0.975, and 1.235 m, respectively. Among these cases, Case M-B showed the lowest temperature distribution in the enclosure and smoke layer temperature, the thinnest smoke layer, and the highest mass flow rate of outflow through the ceiling vent. One of possible reasons for these results is owing to the fact that the behavior of fire plume is changed by the inflow through the side vent. As the visualization result of temperature distribution, to determine the ceiling vent location for the improvement of smoke ventilation performance, it can be important to predict the amount of fire plume inclination by inflow through the side vent and the height of inclined fire plume region. To predict the amount of fire plume inclination by inflow through the side vent, the previous correlations of flame angle were assessed, which under-estimated the fire plume inclination of present numerical simulation.

Evaluation of a Revised AERMOD Treatment of Plume Dispersion in the Daytime Elevated Stable Layer

Advanced dispersion models such as AERMOD specifically address the portion of a plume emitted in convective conditions that is sufficiently buoyant to rise into the stable layer above the elevated inversion. This portion of the plume mass is often referred to as the “penetrated plume” because that plume component breaks through the elevated inversion and penetrates into the stable layer aloft. A pre-mature mixing of the penetrated plume to the ground has been identified in the current formulation of AERMOD, which is the USEPA-preferred short-range dispersion model and used in several other countries. This behavior has been observed based on data from field studies where the model is found to overpredict ground-level concentration events due to the penetrated plume component, with the timing of these peak predictions too early in the day. A proposed update to AERMOD to address the penetrated plume issue (referred to as “HBP” for modifications particularly important for “highly buoyant plume”) is documented and evaluated in this manuscript. The revised approach involves a check on the convective mixing height for the current hour as well as the next hour to determine how much of the penetrated plume has been captured by the convective boundary layer by the end of the current hour. The amount of the penetrated plume mass that is allowed to mix to the ground in the HBP modifications depends upon the result of this calculation. The HBP modification has been evaluated as an update to AERMOD for 3 databases along with a sensitivity analysis of the effects of the HBP changes on a variety of stack heights and buoyancy fluxes. The findings of the evaluation indicate that the HBP changes to AERMOD result in reduced overprediction tendencies. “Implications Statement” for the HBP paper being submitted to JAWMA A proposed enhancement to AERMOD to address a pre-mature mixing of penetrated plume material to the ground has been performed by implemented and evaluated by the authors. The enhancement, referred to as the highly buoyant plume (HBP) is based on work developed by Dr. Jeffrey Weil. HBP is designed to better characterize the penetrated plume behavior in the model such that it aligns more closely with observations based on data from field studies.

Technical note: Interpretation of field observations of point-source methane plume using observation-driven large-eddy simulations

Abstract. This study demonstrates the ability of large-eddy simulation (LES) forced by a large-scale model to reproduce plume dispersion in an actual field campaign. Our aim is to bring together field observations taken under non-ideal conditions and LES to show that this combination can help to derive point-source strengths from sparse observations. We analyze results from a single-day case study based on data collected near an oil well during the ROMEO campaign (ROmanian Methane Emissions from Oil and gas) that took place in October 2019. We set up our LES using boundary conditions derived from the meteorological reanalysis ERA5 and released a point source in line with the configuration in the field. The weather conditions produced by the LES show close agreement with field observations, although the observed wind field showed complex features due to the absence of synoptic forcing. In order to align the plume direction with field observations, we created a second simulation experiment with manipulated wind fields that better resemble the observations. Using these LESs, the estimated source strengths agree well with the emitted artificial tracer gas plume, indicating the suitability of LES to infer source strengths from observations under complex conditions. To further harvest the added value of LES, higher-order statistical moments of the simulated plume were analyzed. Here, we found good agreement with plumes from previous LES and laboratory experiments in channel flows. We derived a length scale of plume mixing from the boundary layer height, the mean wind speed and convective velocity scale. It was demonstrated that this length scale represents the distance from the source at which the predominant plume behavior transfers from meandering dispersion to relative dispersion.

Investigation on direct measurement method of particle velocity in the plume for intelligent laser welding-oriented

The dynamic plume behavior is one of the key features that allows one to obtain the required information for monitoring the process quality of the intelligent laser welding. This paper proposed a method of directly measuring particle velocities in plume induced in fiber laser keyhole welding based on the self-mixing interferometry (SMI) effect. This method was verified by measuring tiny metal objects with known sizes and velocities. The particle velocities can be calculated according to the number of SMI fringes induced by the particles, and the temporal data. To measure the diameters of particles, it is expedient to use a detection laser with a spot diameter larger than that of particles. A smaller diameter of the detection laser spot will result in more accurately measured values of particle velocities. A direct measurement was conducted to assess the particle velocities in the plume induced in fiber laser keyhole welding. These particles in plume had a velocity of 1.9–90 m/s, and more than 45% of these particles had a velocity of 10–60 m/s. Particles with larger diameters were more likely to have higher velocities.

Experimental and Numerical Investigation of Evaluation of Grain Size–Based Porosity Models for Solute Transport through Porous Medium

Uncertainties associated in tracer transport arising through various geological formations are often sorted by laboratory experiments on representative elementary volume (REV). To understand the effect of grain size and packing on plume behavior, tracer transport experiments were performed in fully saturated condition for four different geological materials (glass beads, sand, and coarse and fine natural soil). A mini-aquifer setup having inner dimensions of 150 × 10 × 50 cm was used with sodium chloride (NaCl) as a tracer. The materials were selected to gradually increase the heterogeneity from relatively homogeneous (glass beads) to heterogeneous (natural Himalayan foothill field soil). The aim of the experimental investigation was to study contaminant transport and to examine applicability of various porosity models for particles for a range of geological materials. Simulation of observed breakthrough curves (BTCs) were carried out using a mobile–immobile model (MIM) and continuous time random walk (CTRW) model. Observed experimental breakthrough curves demonstrated relatively symmetrical spreading in glass beads, while natural soil exhibited the presence of preferential flow (physical nonequilibrium). The estimation of porosity from empirical relations deviated significantly from in situ measured porosity. Comparing CTRW and MIM with various porosity model, it is concluded that MIM provided a better representation of observed BTCs.

Experiment and Simulation of One Deep Sewage Discharge Type: Transport of Low‐Salinity Sediment‐Laden Flow Discharged

AbstractDeep sewage discharge leads to inestimable damage to the ambient water (lakes, oceans and reservoirs), which has caused widespread social concern. In the current paper, a three‐dimensional (3D) buoyancy plume model for deep sewage discharge was developed. It simulates sediment‐laden flow with the effects of temperature and salinity differences. Taking the turbulent diffusion coefficient of salinity (αsal) as the calibration parameter, a comparison between the RNG k‐ε and the standard k‐ε models was performed. The proposed model was verified well and agreement with experiment, which proved that the RNG model with the αsal value of 0.4 was the optimal calibration. Then the model was applied to quantify the behavior of the buoyant plume in the ambient fluid (salt water) with respect to different contours of turbulent kinetic energy (k), temperature, salinity and sediment. The dimensionless centerline trajectory positions and boundary positions of them were determined. The results indicated that the discharge of low‐salinity sediment‐bearing water influenced the deep ambient water spatially, both near the free surface and in the vertical plane. Different diffusion and spreading shapes (butterfly, Ginkgo biloba, bean) can be observed on the surface. Accurately evaluating the impact of deep discharge on ambient water has great significance for maintaining healthy and sustainable environments in offshore areas, deep lakes and reservoirs.

Review on Vacuum Laser Beam Welding

Vacuum laser beam welding (VLBW) exhibits better welding characteristics, e.g., deep penetration, less pore, and spatter generation, compared with the conventional laser welding technique under atmospheric pressure. Low ambient pressure affects the vaporization temperature of the base material and the interaction between laser and plasma plume, which affects the behaviors of laser-induced plasma plume, keyhole, and weld pool flow. This review introduces improvements in welding characteristics such as penetration depth, pore, and spatter generation in the VLBW process. The effect of ambient pressure on welding characteristics was reviewed, and the behavior of laser-induced plume, keyhole, and molten pool under reduced ambient pressure was discussed to understand the mechanisms for enhanced weldability.

Effect of molten pool and vapor/plasma plume dynamic behavior of laser-induction hybrid welding on weld formation of S690QL steel

For overcoming the shortcomings of traditional welding methods, laser-induction hybrid welding (LIHW) was investigated. In this paper, high strength low alloy steel S690QL was selected to explore the improvement mechanism of LIHW on weld formation, mainly through high-speed photography, optical microscope and electron back-scattered diffraction (EBSD) techniques to compare the vapor/plasma plume and keyhole dynamic behaviors of laser beam welding (LBW) and LIHW. Both the characteristics of weld joint geometry and microstructure processed by LIHW technology were better than LBW. With increasing inductor output power, the changing period of vapor/plasma plume was accelerated, the spatter defects were inhibited, the molten pool length and width increased. At the same time, due to the better welding heat input absorption and utilization, most the LIHW weld joints contain more ferrite, lower bainite and martensite than LBW weld joint. Furthermore, the alternating magnetic field and the two eruption paths of upper keyhole and lower penetrated hole in LIHW processing could lead to the penetration of LIHW joints, while the LBW does not. Thus, the weld formation mechanism was revealed and compared with LBW, LIHW have better molten pool and vapor/plasma plume dynamic behaviors, which result in the improvement of weld formation.

Effect of longitudinal slope on the smoke propagation and ceiling temperature characterization in sloping tunnel fires under natural ventilation

In order to reduce risk and increase resilience of transportation tunnels, the early-phase detection and protection of fire are of great significance for the safety assessment of tunnel. In this work, numerical simulations are conducted to characterize the thermal plume propagation and ceiling temperature profile in a tunnel with longitudinal slope increasing from 0% to 15%. For the sloping tunnel, as there exists elevation difference between the tunnel ends, the longitudinal air flow will be induced from the lower end. Under such circumstances, the stack effect occurs and it becomes the primary driving force for the smoke movement in tunnel. Results show that the thermal plume behaviors in the sloping tunnel, including the thermal flow field and the temperature profile, show apparently different from those in the horizontal one. The induced air flow rate that directly related to the strength of stack effect is quantified, and on this basis, the predictive correlation of the temperature profile under the ceiling is proposed by considering the influence of the stack effect for different tunnel slopes. Besides, the accuracy and applicability of the obtained correlation are further verified by comparing to a total of four series of previous experimental data with a wider range of tunnel slopes, dimensions, and heat release rates.