Plume Behavior Research Articles

Large eddy simulation of natural convection heat transfer and fluid flow around a horizontal cylinder

Natural convection around a single horizontal cylinder has been extensively studied for heat transfer characteristics, but when coupled with fluid flow, the laminar-to-turbulent transition in buoyant plume poses severe challenge on modelling fidelity and physical interpretability. To address this challenge, this paper conducts detailed verification, validation and analysis of high-fidelity large eddy simulation (LES) for an unconfined horizontal cylinder in water with a Rayleigh number of 8 × 107, complemented by Reynolds-Averaged Navier-Stokes (RANS) computations. To the best of the authors' knowledge, this is the first LES study with acceptable accuracy as validate by experimental data for buoyant plume above a single horizontal cylinder. It is found that LES is far more sensitive to mesh resolution and boundary condition setting than RANS. An alarm is set for the use of periodic condition in LES on lateral boundaries of computational domain due to its inferior accuracy than RANS with transition SST model. The finely-tuned LES with pressure condition on lateral boundaries shows satisfactory agreement with experimental data in terms of heat transfer on cylinder surface and buoyant plume velocity, based on which new physical insight on transitional behavior of thermal plume is obtained. It is found that after leaving the cylinder, buoyant plume is laminar and accelerates, subject to work input from buoyancy force, while its temperature keep decreasing due to heat loss to atmosphere. Flow instability appears first in upward velocity at a streamwise Grashof number of 1.5 × 108, where transition to turbulence onsets. Thermal plume continues to accelerate until it begins to sway horizontally, where energy dissipation into turbulence becomes the major loss mechanism of mean flow energy. Thus, cross-stream diffusivity is augmented notably due to turbulent stresses, leading to smoothing of transverse velocity distribution and reduction of transversely-averaged mean kinetic energy. Transversely-averaged turbulent kinetic energy keeps increasing in transitional regime until the streamwise Grashof number reaches 7 × 109 and then declines to approach an asymptotic value, signifying the end of transition. Overall speaking, buoyancy work dominates the change in mean flow energy, while mean shear outweighs buoyancy in producing turbulent kinetic energy.

Plume analysis from field evaluations of a portable air quality monitoring system

ABSTRACT Near-road measurements in Rochester, NY with a Portable Air Quality Monitoring System indicate a significant plume control of PM2.5 black carbon (BC) concentrations. This study evaluates the performance of two portable air quality enclosures deployed at collocated research sites to determine their accuracy and usefulness in field deployments, and specifically in pollution plume analysis. One system deployed collocated sensors for measurement of particulate matter mass concentration (Thermo pDR 1500 against Tapered Element Oscillating Microbalance (TEOM) measurement) and the second system deployed sensors for measurement of black carbon (Magee AE33 aethalometer and Brechtel Tricolor Absorption Photometer) in ambient and near-road locations in Rochester, New York, respectively. While the optical PM2.5 sensors tended to be biased in their determination of concentration by ~15%, they followed changes and trends in concentration very well. The black carbon sensors in the portable systems agreed very well with each other and with the collocated sensor. As a case study to determine the contribution from statistically significant short-lived excursions of pollutant concentration, Morlet wavelet analysis was performed on data from the portable system sensors. Black carbon was found to be strongly influenced by plume behavior with significant plume excursions representing just over 12% of all data points and contributing on average 1 µg/m3 of black carbon above ambient concentrations. Implications: This paper first evaluates two air pollutant monitoring enclosures with wide applicability including near-road detection of pollutants. Then, we present a novel method to designate isolate statistically significant excursions in air pollution concentration which can be used to determine the impact of pollutant plumes as observed in PM and black carbon behavior near road.

The investigation of arc fluctuations in thermal plasma torch using 3D modeling approach

Two and three-dimensional transient models of a thermal plasma torch are presented to analyse the effect of operating conditions on arc root fluctuations for various types of anode configuations. The computational fluid dynamics code, OpenFOAM(c), is utilised in a modified form to model the arc and plasma flow inside the argon plasma torch. Modeling a thermal plasma requires a combination of mutually related fluid dynamics and electromagnetic phenomena which dictate the size and stability of the arc column. While the 2D axisymmetric model is effective in depicting the average energy and average velocity profiles of plasma gas, it fails to describe the fluctuations in arc behaviour and its mode of attachment on the anode. In a 3D model, the arc movement is captured in both axial and azimuthal directions wherein the arc-root attachment on anode surface seems to fluctuates in a periodic manner and the voltage fluctuations mirrors the arc-root attachment behaviour within the system. We have here investigated the effect of operating conditions on the frequency of this arc reattachment, finding that the input current and gas flow rate have a significant effect on arc behaviour. We have also reported the effect of arc voltage perturbations on the exit plume properties (velocity and average temperature) and finally the effect of anode nozzle geometry on the fluctuations and plume behavior is presented.

Understanding Contaminant Migration Within a Dynamic River Corridor Through Field Experiments and Reactive Transport Modeling

The behavior of a persistent uranium plume within an extended river corridor at the DOE Hanford site is dominantly controlled by river stage fluctuations in the adjacent Columbia River. The plume behavior is further complicated by substantial heterogeneity in physical and geochemical properties of the host aquifer sediments. Multi-scale field and laboratory experiments and reactive transport modeling were integrated to understand the complex plume behavior influenced by highly variable hydrologic and geochemical conditions in time and space. In this paper, we (1) describe multiple data sets from field-scale uranium adsorption and desorption experiments performed at our experimental well-field, (2) develop a reactive transport model that incorporates hydrologic and geochemical heterogeneities characterized from multi-scale and multi-type datasets and a surface complexation reaction network based on laboratory studies, and (3) compare the modeling and observation results to provide insights on how to refine the conceptual model and reduce prediction uncertainties. The experimental results revealed significant spatial variability in uranium adsorption/desorption behavior, while modeling demonstrated that ambient hydrologic and geochemical conditions and heterogeneities in sediment physical and chemical properties both contributed to complex plume behavior and its persistence. This research underscores the great challenges in adequately characterizing this type of site to model the reactive transport processes over scales of 10 m or more. Our analysis provides important insights into the characterization, understanding, modeling, and remediation of groundwater contaminant plumes influenced by dynamic surface water and groundwater interactions.

Wildfire Smoke Particle Properties and Evolution, From Space-Based Multi-Angle Imaging II: The Williams Flats Fire during the FIREX-AQ Campaign

Although the characteristics of biomass burning events and the ambient ecosystem determine emitted smoke composition, the conditions that modulate the partitioning of black carbon (BC) and brown carbon (BrC) formation are not well understood, nor are the spatial or temporal frequency of factors driving smoke particle evolution, such as hydration, coagulation, and oxidation, all of which impact smoke radiative forcing. In situ data from surface observation sites and aircraft field campaigns offer deep insight into the optical, chemical, and microphysical traits of biomass burning (BB) smoke aerosols, such as single scattering albedo (SSA) and size distribution, but cannot by themselves provide robust statistical characterization of both emitted and evolved particles. Data from the NASA Earth Observing System’s Multi-Angle Imaging SpectroRadiometer (MISR) instrument can provide at least a partial picture of BB particle properties and their evolution downwind, once properly validated. Here we use in situ data from the joint NOAA/NASA 2019 Fire Influence on Regional to Global Environments Experiment-Air Quality (FIREX-AQ) field campaign to assess the strengths and limitations of MISR-derived constraints on particle size, shape, light-absorption, and its spectral slope, as well as plume height and associated wind vectors. Based on the satellite observations, we also offer inferences about aging mechanisms effecting downwind particle evolution, such as gravitational settling, oxidation, secondary particle formation, and the combination of particle aggregation and condensational growth. This work builds upon our previous study, adding confidence to our interpretation of the remote-sensing data based on an expanded suite of in situ measurements for validation. The satellite and in situ measurements offer similar characterizations of particle property evolution as a function of smoke age for the 06 August Williams Flats Fire, and most of the key differences in particle size and absorption can be attributed to differences in sampling and changes in the plume geometry between sampling times. Whereas the aircraft data provide validation for the MISR retrievals, the satellite data offer a spatially continuous mapping of particle properties over the plume, which helps identify trends in particle property downwind evolution that are ambiguous in the sparsely sampled aircraft transects. The MISR data record is more than two decades long, offering future opportunities to study regional wildfire plume behavior statistically, where aircraft data are limited or entirely lacking.

Experimental and numerical study on gas release and dispersion from underwater soil

This paper focuses on the dispersion behavior of gas released from underwater soil by using experimental and numerical approaches. A small-scale experimental system is developed and a number of release scenarios are carried out. The results indicate that the released gas breaks through the sand layer after consuming a certain amount of initial energy and enters the water in the form of bubble plumes, which is similar to the theoretical model. The plume interacts intensely with the surface and forms a fountain with a periodic change in height. The effect of leak pressure, water depth and buried depth on plume behavior and critical parameters including plume diameter, fountain height and rise time are discussed. The experimental data are also utilized to verify the effectiveness of the presented numerical model using Eulerian-Eulerian volume of fluid (VOF) approach. The validated numerical model is subsequently employed to analyze three full-scale scenarios, and the results show good consistency with the experiments. Both the experiments and numerical models are of great value for evaluating the consequences of gas released from underwater buried pipelines and providing data and theoretical support for the subsequent risk assessment.

Analysis of vapor plume and keyhole dynamics in laser welding stainless steel with beam oscillation

The influence of laser welding with beam oscillation on dynamic behavior of vapor plume, melt pool and keyhole was investigated. The stability of plume morphology is improved with a little fluctuation, and the height and area of plasma plume are decreased as the oscillation frequencies increased. The melt pool morphologies and flowing feature under beam oscillation conditions are also regulated due to the resultant energy deposition, which has an influence on weld solidification process. The re-melting effect of circular beam oscillation can eliminate pores formation and improve weld quality.

Influence of volume blockage ratio on turbulent buoyant plume dispersion in mixed ventilated tunnel

The objective of this study is to numerically investigate the effects of volumetric blockage ratio on the thermal plume behavior in a mixed ventilated tunnel with heat source and vehicular blockage. The tunnel model consists of three naturally ventilated roof openings and longitudinal ventilation is provided by supplying forced air through the tunnel inlet port. The non-Boussinesq variable density approach is used to model the high thermo-buoyant flows with large eddy simulations (LES) turbulence model discretized by finite difference method (FDM). The investigation is performed by varying the Grashof number (Gr) in the range 108≤Gr≤ 1010 and the forced ventilation velocity (Uc) and volumetric blockage ratio (ξ) are varied between 0.05 ≤Uc≤ 0.5 and 0.012 ≤ ξ ≤ 0.05. The outcome of this study emphasizes that the longitudinal ventilation and volume blockage ratio significantly affects the thermal plume behavior and venting efficiency of the roof openings. It is found that inertial force from forced air increases the mass flow rate through downstream vent in comparison with the upstream vent. It is observed that the increase in Grashof number enhances the bidirectional exchange rate through roof vents and an increase in volume blockage ratio decreases the discharge rate through the roof openings.

Morphology and flow behavior of buoyant bubble plumes

The morphological and hydrodynamic behavior of bubbles in air–water plumes was studied by employing Particle Tracking Velocimetry (PTV) techniques. Individual bubbles were identified by analyzing the instantaneous high-speed camera images of the plume. The bubble velocities were then obtained by Lagrangian tracking of each bubble, based on its size and location. The nature of bubble coalescence and breakup was also investigated based on the change in the projected area of the parent and daughter bubbles. The effect of the bubble position and the air inflow rate on the bubble properties like diameter, aspect ratio, velocity, number flux, etc., and on the coalescence and breakup behavior was investigated. A novel correlation is proposed to estimate the bubble aspect ratio as a function of bubble Reynolds number and Eotvos number, for a wide range of flow conditions, and is compared with existing correlation from the literature.

Temporal flow variations interact with spatial physical heterogeneity to impact solute transport in managed river corridors

The interactions between surface water and groundwater in river corridors lead to temporal fluctuations in subsurface water fluxes which have a critical role on solute transport dynamics. In this work, we develop a framework to analyze the relative impacts of different temporal frequencies of the flow field in a spatially heterogeneous aquifer on solute transport. Our analysis indicates that the advection-dispersion equation behaves as a low-pass filter by wiping out the effect of high-frequency velocity fluctuations on the first two spatial moments of the solute plume, namely its center of mass and spreading. The concepts discussed in the theoretical analysis are then applied to understand solute transport dynamics at the 300 Area of the Hanford site (USA) adjacent to the Columbia River. We examine the temporal behavior of the solute plume's spatial moments for different temporal frequencies utilizing geostatistical parameters estimated in the 300 Area. Due to the proximity to the Columbia river, groundwater fluxes at the Hanford site are highly dynamic resulting in a large range of characteristic temporal frequencies. Nonetheless, similar to the theoretical analysis, our results show that the effect of high-frequency fluctuations is filtered, with most of the solute transport dynamics being controlled by fluctuations characterized by a large characteristic period.

Buoyant and countercurrent flow of CO2 with capillary dispersion

Analytical modeling of CO2 flow is essential for the rapid evaluation of CO2 plume evolution and possible leakage risk during geological carbon sequestration (GCS). Here we adapt the model of describing the secondary migration of oil proposed by Siddiqui and Lake (1992) to characterize CO2 upward migration and backfilling for buoyant and countercurrent flow in a saline aquifer. Both water- and CO2-wet reservoirs are examined under typical buoyant fluxes.We present self-similar solutions of CO2 saturation waves without capillary pressure and traveling wave solutions after adding capillarity. We demonstrate that saturation wave types, CO2 migration, and saturation profiles are influenced by buoyant flux, capillary pressure, wettability, and relative permeability. The stabilized zones resulting from capillary dispersion inside a CO2-wet reservoir generally extend wider than those for a water-wet reservoir. The presented model and results are potentially useful to understand field scale CO2 plume behaviors as well as to guide the design of corefloods for studying CO2 buoyant flow characteristics.

Fenômeno de meandro do vento e a função de autocorrelação calculada com base na concentração de poluentes simulada pelo modelo transiente 3D-GILTT

The aim of this work is to present a pollutants dispersion transient model in low wind conditions to simulate the behavior of the pollutants plume in the atmosphere, considering in the model the u e v horizontal wind components simulated by the LES-PALM model. The dispersion model is based in the advection-diffusion equation and represent by this methodology the wind meandering phenomenon. The Generalized Integral Laplace Transform Technique in three dimensions (3D- GILTT) solves the transient advection-diffusion equation. The data utilized to initialize the simulations are data of the low wind INEL (Idaho National Engineering Laboratory) experiment accomplished in EUA. The results show that the dispersion model reproduces the wind meandering phenomenon, in other words, the autocorrelation function of the concentration simulated over an hour presents the negative lobule, similarly to observed lobules in the u and v wind components. Therefore, the model simulates the pollutants plume in a satisfactory way and can be used to air quality regulatory applications in low wind and wind meandering conditions.

A Review on Multiphase Underwater Jets and Plumes: Droplets, Hydrodynamics, and Chemistry

AbstractJets and plumes have been the focus of quantitative investigations since the mid‐1950s. These investigations intensified following the Deepwater Horizon oil spill, in which thousands of tons of oil and natural gas were released into the Gulf of Mexico. This review focuses on plume dynamics that apply to both single‐phase and multiphase liquid‐in‐liquid and liquid plus gas into liquid plumes, including bubble and droplet formation, and heat and mass transfer. Broadly, our work highlights several previously unknown or overlooked aspects of multiphase flow in the deep oceans. Upstream of the jet release, multiphase hydraulics can significantly affect the turbulence, for instance, through churn flow that enhances the turbulence in the free jet, affecting the conditions where bubbles and droplets are formed. Droplet formation was a major focus recently, with experiments covering a range of scales and flow rates of oil and gas at low and high pressure. Detailed observations of droplet formation at the jet‐water boundary reveal the formation of compound droplets, which are emulsions of oil and water with implications for mass conservation and mass transfer. At the plume scale, integral models have been adapted to include the complex thermodynamics and chemistry of oil and gas plumes. In parallel, significant advances were made in numerical simulations of multiphase plumes through large eddy simulations by treating the oil and gas either a continuous or discrete phase. Through this work, a vivid picture of the complex droplet, chemical, and hydrodynamic behavior of multiphase plumes in the ocean is emerging.

Review of developments in air quality modelling and air quality dispersion models

Air dispersion models are mathematical tools used for simulating the physical and chemical processes governing the diffusion and transformation of pollutants in the atmosphere. The simplest dispersion models are steady-state Gaussian plume models. They are based on mathematical approximation of the plume behaviour and follow some basic assumptions that may not always present a realistic scenario. Despite having these limitations, they provide reasonable results when used aptly. More recently, advanced dispersion models are being developed, which are based on a more refined approach of simulating the dispersion phenomenon following the properties of the atmosphere rather than relying on general mathematical approximation. This has expanded the field of modelling to tackle difficult situations such as complex terrain and long-distance transport. In this review paper, the developments in air quality modelling, with emphasis on dispersion modelling, are presented. Further, a few models are selected representing different categories in dispersion modelling, which are Gaussian models – American Meteorological Society/Environmental Protection Agency Regulatory Model, Caline4, Airviro Gauss, Complex Terrain Dispersion Model and Fugitive Dust Model; Eulerian models – California Grid Model, Flexible Air Quality Regional Model and Panache; Lagrangian models – Graz Lagrangian Model, Flexible Particle Dispersion Model, Austal2000 and Hybrid Single Particle Lagrangian Integrated Trajectory Model; and advanced dispersion models – UK–Atmospheric Dispersion Modelling System 5, The Air Pollution Model and Calpuff. A comparison has been done based on certain characteristic features obtained from various publications.

Investigation of Plume Offset Characteristics in Bubble Columns by Euler–Euler Simulation

Based on low-cost and easy to enlarge, the bubble column device has been widely concerned in chemical industry. This paper focuses on bubble plumes in laboratory-scale three-dimensional rectangular air-water columns. Static behavior has been investigated in many experiments and simulations, and our present investigations consider the dynamic behavior of bubble plume offset in three dimensions. The investigations are conducted with a set of closure models by the Euler–Euler approach, and subsequently, literature data for rectangular bubble columns are analyzed for comparison purposes. Moreover, the transient evolution characteristics of the bubble plume in the bubble column and the gas phase distribution in sections are introduced, and the offset characteristics and the oscillation period of the plume are analyzed. In addition, the distributions of the vector diagram of velocity and vortex intensity in the domain are given. The effects of different fluxes and column aspect ratios on bubble plumes are studied, and the offset and plume oscillation period (POP) characteristics of bubbles are examined. The investigations reveal quantitative correlations of operating conditions (gas volume flux) and aspect ratios that have not been reported so far, and the simulated and experimental POP results agree well. An interesting phenomenon is that POP does not occur under conditions of a high flux and aspect ratio, and the corresponding prediction values for the conditions with and without POP are given as well. The results reported in this paper may open up a new way for further study of the mass transfer of bubble plumes and development of chemical equipment.

The Variation of the Salt Concentration at the Discharge of a River into a Saline Water

Abstract A plume model is used to describe the variation of the salt concentration at the discharge of a river into a saline water. The integral model of the plume behavior consists of a set of ordinary differential equations derived from conservation of mass, momentum and salt concentration. The temperatures of the plume and ambient saline water are considered equal. The concentration of the salt in the river water is null. The saline water is assumed motionless. After release from the river, the concentration of the salt in the plume increases by mixing with the ambient saline water. The rate of mixing depends upon the local plume and ambient fluid properties such as velocity and salt concentration.

Application of temporal moments to interpret solute transport with time-dependent dispersion

Temporal moments of solute transport through porous media are calculated to analyze the time average spatial distribution of solute plume. Simulation of spatially and temporally distributed breakthrough curves (BTCs) is computationally rigorous and lacking the explanation about overall plume evolution within porous media. However, temporal moment provides an attractive and simple solution to study the plume behavior. In this study, temporal moments are presented to interpret solute plume behavior in heterogeneous porous media such as hydraulically coupled stratified porous media with different time-dependent dispersion models. Governing equations of solute transport have been solved numerically using Crank-Nicolson scheme, and further solute concentration data has been utilized to calculate moments of solute concentration using numerical integration. The effect of various parameters such as mass-transfer coefficient, pore-water velocity, time-dependent dispersion coefficients, and porosity of mobile region on the transport of solute has been studied through sensitivity analyses. Temporal moment analysis revealed that the mass recovery, mean residence time, and variance are sensitive to the estimated parameters. Numerical results suggested that the asymptotic time-dependent dispersion function with mobile–immobile model represents the plume spreading through heterogeneous porous media in a more realistic manner.

Plume simulation of liquid apogee engine for GEO satellite using parallel DSMC method

For satellite design engineers, an exhaust plume from a liquid rocket engine has been classified as a potential source of local heat load and surface contamination on payload sensors or equipment because several kinds of chemical species at relatively high temperatures can severely impact on the performance of optically-sensitive components. Hence, an accurate prediction of plume influence on a given satellite configuration is an essential task for the satellite development process. In this sense, the objective of the present study was to focus on a numerical investigation of the detailed plume behavior of a liquid apogee engine (LAE) and its influence on a geostationary orbit (GEO) satellite. To deal with different continuum and rarefied flow regimes for the inside and outside of an engine nozzle during LAE operation, a combined approach of computational fluid dynamics (CFD) and parallelized Direct Simulation Monte Carlo (DSMC) was used to simulate the plume flow efficiently. Using the simulation results of the present study, the detailed plume behavior of the LAE and its influence were evaluated and analyzed on a three-dimensional satellite configuration during the early orbit raising phase condition.

The Use of a Numerical Weather Prediction Model to Simulate Near-Field Volcanic Plumes

In this paper, a state-of the art numerical weather prediction (NWP) model is used to simulate the near-field plume of a Plinian-type volcanic eruption. The NWP model is run at very high resolution (of the order of 100 m) and includes a representation of physical processes, including turbulence and buoyancy, that are essential components of eruption column dynamics. Results are shown that illustrate buoyant gas plume dynamics in an atmosphere at rest and in an atmosphere with background wind, and we show that these results agree well with those from theoretical models in the quiescent atmosphere. For wind-blown plumes, we show that features observed in experimental and natural settings are reproduced in our model. However, when comparing with predictions from an integral model using existing entrainment closures there are marked differences. We speculate that these are signatures of a difference in turbulent mixing for uniform and shear flow profiles in a stratified atmosphere. A more complex implementation is given to show that the model may also be used to examine the dispersion of heavy volcanic gases such as sulphur dioxide. Starting from the standard version of the weather research and forecasting (WRF) model, we show that minimal modifications are needed in order to model volcanic plumes. This suggests that the modified NWP model can be used in the forecasting of plume evolution during future volcanic events, in addition to providing a virtual laboratory for the testing of hypotheses regarding plume behaviour.

Minimizing the scrubbed flue gas concentration near ground by appropriate selection of sources in a tandem arrangement of cooling towers

The wet scrubbing is one of the effective techniques to reduce the pollutant concentration in the power plants. The low temperature scrubbed flue gas can be added to the outlet buoyant plume of a cooling tower to reach the desired altitude. In large power plants, there are a number of cooling towers located in different arrangements with respect to the wind direction. A tandem layout of the towers leads to a more complicated flow geometry to analyze as the flow outlet from each source is highly affected by others. In this study, the behavior of outlet plumes from single cooling tower, as well as tandem arrangements of sources with two, three and four towers are investigated to discover the more appropriate towers for the scrubbed flue gas to be released from. An additional species transport equation is included to the set of governing equations per each added cooling tower in order to recognize the contribution of each tower in the pollutant concentration at any point in the flow. This innovative numerical modeling technique makes it possible to clearly distinguish the details of the outflow from each cooling tower in the course of the flow. The interactions between the outlet plumes are explained by analyzing the vortex behavior and pressure distribution which are strongly affected by the number of the cooling towers in the wind direction.