Plume Velocity Research Articles

North Polar Spur: Gaseous plume(s) from star-forming regions ~3-5 kpc from the Galactic Center?

We argue that the North Polar Spur (NPS) and many less prominent structures are formed by gaseous metal-rich plumes associated with star-forming regions (SFRs). The SFRs located at the tangent to the 3-5 kpc rings might be particularly relevant to the NPS. A multi-temperature mixture of gaseous components and cosmic rays rises above the Galactic disk under the action of their initial momentum and buoyancy. Eventually, the plume velocity becomes equal to that of the ambient gas, which rotates with different angular speeds than the stars in the disk. As a result, the plumes acquire characteristic bent shapes. An ad hoc model of plumes' trajectories shows an interesting resemblance to the morphology of structures seen in the radio continuum and X-rays.

Self-correction of the optical distortion effect of thermal plumes in particle image velocimetry

Optical distortion caused by changes in the refractive index of fluid flow is a common issue in flow visualization using techniques, such as particle image velocimetry (PIV). In thermally driven convection, this distortion can severely interfere with PIV results due to the ubiquitous density and, therefore, refractive index heterogeneity in the fluid. The distortion also varies spatially and temporally, adding to the challenge. We propose a composite filter, the shadow-affected PIV region filter, which combines a series of conventional image filters to address this issue, focusing on optical distortion of thermal plumes in laminar flow. We verify the effectiveness of the filter using both synthetic particle images created from ray tracing and real particle images from the laboratory. For the first time, we effectively mitigate the optical distortion from plumes while preserving the in-plane plume velocity and overall flow pattern, with the PIV data alone. Our filter is efficient and does not require additional measurements, expensive ray tracing, or a large dataset to begin with. It can be extended to separate the flow field and the effect of optical distortion in other fluid experiments when the two components are visually distinct. Additionally, this filter can serve as a baseline algorithm for comparison when developing more advanced methods like neural networks.

Bерифікація алгоритму методу пробних частинок на задачі осьового обтікання конуса розрідженим газовим струменем

This paper is concerned with an aerodynamic calculation of supersonic gas plume flows and the determination of the forces they exert on obstacles. The paper presents a development of the test particle statistical method (TPSM) to numerically simulate supersonic gas plumes over a wide range of flow conditions. The work is based on the idea of a combined approach, i.e., the use of the gas-dynamic parameter distribution at the nozzle exit or on the conventional boundary of the dense core of the plume as input data for a TPSM algorithm adapted from homogeneous flows to plume ones. Combining methods of continual aerodynamics (inside or near the nozzle, where a continuum flow takes place) and the TPSM (where the motion is described on a molecular-kinetic level) allows one to solve supersonic plume efflux problems for arbitrarily rarefied plumes. The TPSM plume algorithm was tested to verify its reliability on the problem of axial flow past a cone. At the initial stage of the use of the combined approach, consideration was given to a rather rarefied gas flow, for which the gas-dynamic parameters at the nozzle exit can be used as TPSM input data. The force distribution over the cone surface and the static pressure upstream of the cone were calculated. The TPSM results were found to be in satisfactory agreement with the available direct simulation Monte-Carlo and experimental data. It was concluded that using the plume velocity and density distributions at the continual zone exit found from the Navier–Stokes equations as TPSM input data would significantly improve the expected results. This use of the TPSM in an aerodynamic calculation of gas plumes is the first in Ukraine. The TPM offers saving in computational resources: the TPSM running time depends on a variety of factors, but it is many times shorter than that of the direct simulation Monte Carlo method.

Correlation Between Dynamic Spray Plume and Drug Deposition of Solution-Based Pressurized Metered-Dose Inhalers.

Background: The lack of visual dynamic spray characterization has made the understanding of the physical processes governing atomization and drug particle formation difficult. This study aimed to investigate the changes in the spray plume morphology and aerodynamic particle size of solution-based pressurized metered-dose inhalers (pMDIs) under different conditions to achieve better drug deposition. Methods: Solution-based pMDIs were studied, and the effects of various factors, such as propellant concentration, orifice diameters, and atomization chamber volume, on drug deposition were examined by analyzing the characteristics of spray plume and aerodynamic particle size. Results: Reducing the actuator orifice and spray area led to a concentrated spray plume and increased duration and speed. Moreover, the aerodynamic particle sizes D50 and D90 decreased, whereas D10 remained relatively unchanged. Decreasing the atomization chamber volume of the actuator led to reduced spray area and an increased duration but a decreased plume velocity. D90 exhibited a decreasing trend, whereas D10 and D50 remained relatively unchanged. Reducing the propellant concentration in the prescription, the spray area and the plume velocity first decreased and then increased. The duration initially increased and then decreased. The values of D50 and D90 showed an initial decreasing followed by an increasing trend, whereas D10 remained relatively unchanged. Conclusions: During the development process, attention should be paid to the changes in the spray area, spray angle, duration, and speed of the spray plume. This study recommended analyzing the characteristics of the spray plume and combining the data of two or more aerodynamic particle size detection methods to verify the deposition in vitro to achieve rapid screening and obtain high lung deposition invivo.

Study on the plume flow behavior and air entrainment characteristics of co-burning fires

In most of the fire accidents, there is large oil layer leaking into the fire dike and multiple fire points burning simultaneously. A series of numerical simulations for co-burning of a dike and double tanks (co-burning) with different spacing S have been conducted to study the plume flow behavior and air entrainment characteristics. The simulation results show that there is a conical fuel-rich region on the upper rim of the tank which results in the entrained air to flow circularly along the surface of the conical region. With the increase of S, the restriction effect of tank sidewall on air entrainment from environment enhances, while the restriction degree of air entrainment in the middle area of the double tanks decreases, affecting the distribution of plume velocity field and temperature field. And under the coupling effect of them, the tilt degree of tank flame decreases with the increase of S (from 0.3 m to 0.7 m). The air entrainment restriction coefficient αB, αS are introduced to characterize the restriction effect of air entrainment between the external dike fire and the double tank fires. Based on this, a co-burning plume entrainment model has been established, which can be applicable to different spacing S.

Flow-field characteristics of the thermal plume above an elliptical high-temperature heat source surface

The thermal plume formed by the high-temperature elliptical heat source surface during the smelting process is often captured and removed by the local exhaust system. Accurately mastering the flow-field characteristics of such high-temperature elliptical heat plumes is helpful for efficient design of local exhaust systems. In this paper, the effects of the ratio of long and short axes (5/4 ≤ ξ ≤ 5/1) and the intensity of heat source (80 ≤ F ≤ 160 W) on the axial and radial velocity distribution of thermal plume in an elliptical heat source are investigated by numerical simulation combined with experimental validation. The results show that in the range of ξ ≤ 5/1, the axial dimensionless velocity distribution of the elliptical plume field and the spreading range of the plume field are mainly affected by ξ instead of F. For 5/4 ≤ ξ ≤ 5/1, the maximum axial velocity Um appears at 1.7 to 2.7 times Z/L (plume height to heat source long axis ratio). For ξ ≤ 5/2, the height at which the cross-sectional velocity field transitions to a circular distribution aligns with the height of Um. It is found that the plume velocity field is characterized by applying the point source model for ξ ≤ 5/3, and vice versa for the linear source model. The plume flow rate formulation obtained by modifying the linear source model for ξ > 5/3 has a better predictive ability in the Z/L ≤ 5 region. This study provides a reference for the design of ventilation systems for elliptical surface heat sources.

Multi-Height and Heterogeneous Sensor Fusion Discriminant with LSTM for Weak Fire Signal Detection in Large Spaces with High Ceilings

Fire is a significant cause of fatalities and property loss. In tall spaces, early smoke dispersion is hindered by thermal barriers, and initial flames with limited smoke production may be obscured by ground-level structures. Consequently, smoke, temperature, and other fire sensor signals are weakened, leading to delays in fire detection by sensor networks. This paper proposes a multi-height and heterogeneous fusion discriminant model with a multilayered LSTM structure for the robust detection of weak fire signals in such challenging situations. The model employs three LSTM structures with cross inputs in the first layer and an input-weighted LSTM structure in the second layer to capture the temporal and cross-correlation features of smoke concentration, temperature, and plume velocity sensor data. The third LSTM layer further aggregates these features to extract the spatial correlation patterns among different heights. The experimental results demonstrate that the proposed algorithm can effectively expedite alarm response during sparse smoke conditions and mitigate false alarms caused by weak signals.

Circulation and Retention of River Plumes Around Capes

AbstractRiver plumes often interact with capes in the coastal ocean, impacting local hydrodynamics and the transport of scalars. However, our current knowledge on how capes affect river plume separation, mixing, and retention is limited. Here, we conducted idealized numerical experiments with Gaussian‐shaped capes of varying curvature radii, constant river discharge, a sloping bottom, and scenarios with and without downwelling winds. We found that river plumes separate from capes when the Rossby number is above 1, a criterion that had not been tested for plume separation. This Rossby number is based on the plume velocity, the Coriolis factor, and the radius of curvature of the cape. Freshwater accumulation is greatest at the lee of narrow (i.e., pointy) capes under calm winds, but decreases significantly in downwelling winds or around broader capes.

Aerosol Plumes of Inhalers Used in COPD.

The selection of inhaler device is of critical importance in chronic obstructive pulmonary disease (COPD) as the interaction between a patient's inhalation profile and the aerosol characteristics of an inhaler can affect drug delivery and lung deposition. This study assessed the in vitro aerosol characteristics of inhaler devices approved for the treatment of COPD, including a soft mist inhaler (SMI), pressurized metered-dose inhalers (pMDIs), and dry powder inhalers (DPIs). High-speed video recording was used to visualize and measure aerosol velocity and spray duration for nine different inhalers (one SMI, three pMDIs, and five DPIs), each containing dual or triple fixed-dose combinations of long-acting muscarinic receptor antagonists and long-acting β2-agonists, with or without an inhaled corticosteroid. Measurements were taken in triplicate at experimental flow rates of 30, 60, and 90 l/min. Optimal flow rates were defined based on pharmacopoeial testing requirements: 30 l/min for pMDIs and SMIs, and the rate achieving a 4-kPa pressure drop against internal inhaler resistance for DPIs. Comparison of aerosol plumes was based on the experimental flow rates closest to the optimal flow rates. The Respimat SMI had the slowest plume velocity (0.99 m/s) and longest spray duration (1447 ms) compared with pMDIs (velocity: 3.65-5.09 m/s; duration: 227-270 ms) and DPIs (velocity: 1.43-4.60 m/s; duration: 60-757 ms). With increasing flow rates, SMI aerosol duration was unaffected, but velocity increased (maximum 2.63 m/s), pMDI aerosol velocity and duration were unaffected, and DPI aerosol velocity tended to increase, with a more variable impact on duration. Aerosol characteristics (velocity and duration of aerosol plume) vary by inhaler type. Plume velocity was lower and spray duration longer for the SMI compared with pMDIs and DPIs. Increasing experimental flow rate was associated with faster plume velocity for DPIs and the SMI, with no or variable impact on plume duration, whereas pMDI aerosol velocity and duration were unaffected by increasing flow rate.

Improved Olfactory Deposition of Theophylline Using a Nanotech Soft Mist Nozzle Chip.

Currently, nasal administration of active pharmaceutical ingredients is most commonly performed using swirl-nozzle-based pump devices or pressurized syringes. However, they lead to limited deposition in the more active regions of the nasal cavity, especially the olfactory region, which is crucial for nose-to-brain drug delivery. This research proposes to improve deposition in the olfactory region by replacing the swirl nozzle with a nanoengineered nozzle chip containing micrometer-sized holes, which generates smaller droplets of 10-50 μm travelling at a lower plume velocity. Two nanotech nozzle chips with different hole sizes were tested at different inhalation flow rates to examine the deposition patterns of theophylline, a hyposmia treatment formulation, using a nasal cavity model. A user study was also conducted and showed that the patient instructions influenced the inhalation flow rate characteristics. Targeted flow rates of between 0 and 25 L/min were used for the in vitro deposition study, yielding 21.5-31.5% olfactory coverage. In contrast, the traditional swirl nozzle provided only 10.8% coverage at a similar flow rate. This work highlights the potential of the nanotech soft mist nozzle for improved intranasal drug delivery, particularly to the olfactory region.

Chinese expert consensus on standardized inhaler device application in stable chronic airway diseases (2023)

Chinese expert consensus on standardized inhaler device application in stable chronic airway diseases (2023)

Increased Melting of Marine‐Terminating Glaciers by Sediment‐Laden Plumes

AbstractThis paper summarizes the results of the first investigation into the effect of particle‐laden plumes on glacier melting using laboratory experiments. We find that the melt rate, when the ice is exposed to a particle‐laden plume, can be larger than when exposed to an equivalent plume without particles. The increased melt rate is linked to an increase in the plume velocity in response to the presence of suspended particles. Including this increased velocity in a plume model improves melt rate predictions from the “three‐equation model” by approximately 45% for the range of particle concentrations used in this study.

Numerical study of the convective heat transfer coefficient for steel column surrounded by localized fires

The convective heat transfer coefficient hc characterizes the heat transfer capacity between the fluid-solid interface in a thermal convection phenomenon. At present, values adopted from specifications are mostly used to define the hc coefficients in localized fire researches. In this paper, the specific scenario of the steel column surrounded by fire plume is selected as a typical case to explore the surface hc change rules of the steel column under the action of the fire source at the bottom. Different from the application of the concept of adiabatic surface temperature (AST) to achieve fluid-solid thermal coupling, this paper takes the scenario with the fire source heat release rate (HRR) being 81 kW as an example and conducts a two-way coupling simulation analysis of the fire and the thermal models by means of CFD codes. First, the validity of this simulation methodology is verified by comparing the results of the numerical model and the experiment. Following this, the distribution laws of the spatial velocity and temperature fields are analyzed, and the hc coefficient of the steel column surface is explored in detail using theoretical formula and traditional empirical formula respectively. It is noted that the hc results obtained based on theoretical formula can comprehensively consider the velocity boundary layer and temperature boundary layer situations above the column surface, which is a direct result of the definition of the convective heat transfer coefficient. It is found that the hc‾ is lower at the bottom of the column and increases with height, with relative maximum value in the lower and middle parts of the column, reaching around 40 W/m2 K. The hc‾ results decrease along the axial direction, with the value of upper part of the column being about 20 W/m2 K. In contrast, the hc‾ distributions along the height obtained by the empirical formulas are similar to the distribution of fire plume velocity along the height. In other words, it considers only the effect of the velocity boundary layer, while the effect of significant changes in fluid temperature on convective heat transfer behavior is less considered. Compared to the results based on the theoretical definition, the hc‾ results obtained by empirical formulas are significantly smaller in the lower and middle parts of the column, and higher at the top of the column. Finally, a new hc‾ practical formula for the column surfaces surrounded by fire plume is proposed, which agrees well with the results based on the theoretical definition in several cases.

Steady-state sound propagation through hot exhaust jets in cooler cross-flow: A computational study

An analysis has been carried out to investigate the sound radiation through a heated jet in cooler cross-flow, which is representative of many industrial exhaust systems, using a hybrid steady-state computational fluid dynamics and computational acoustic model. The mean flow and temperature fields are modelled using steady-state computational fluid dynamics, with the turbulence modelled using Reynolds Averaged Navier-Stokes equations. The corresponding mean flow and temperature fields are used in the computational sound propagation model using linearised acoustic wave equation with mean flow based on a scalar flow potential. The results obtained from the computational simulations show that the flow significantly changes the sound propagation path and that the sound levels downstream of the duct outlet are higher than expected from using an acoustic monopole radiation pattern. The dominant mechanism affecting the propagation of sound is the refraction arising from the plume's temperature and velocity gradients. The sound propagation is highly dependent on the proximity from the duct outlet, normalised wavenumber, temperature and the jet to cross-flow mean velocity ratio. This computational study builds upon previous experimental work to analyse the fluid-acoustic interaction for heated jets in cooler cross-flow to understand the complex radiation pattern that leads to higher-than-expected sound levels downstream of the duct outlet.

An analytical model for the velocity and gas fraction profiles near gas-evolving electrodes

Understanding multiphase flow close to the electrode surface is crucial to the design of electrolyzers, such as alkaline water electrolyzers for the production of green hydrogen. Vertical electrodes develop a narrow gas plume near their surface. We apply the integral method to the mixture model. Considering both exponentially varying and step-function gas fraction profiles, we derive analytical relations for plume thickness, velocity profile, and gas fraction near the electrode as a function of height and current density. We verify these analytical relations with the numerical solutions obtained using two-dimensional mixture model simulations. We find that for low gas fractions, the plume thickness decreases with an increase in current density for an exponentially varying gas fraction profile. In contrast, the plume thickness increases with increasing current density at high gas fractions for an approximately step-function-shaped gas fraction profile, in agreement with experiments from the literature.

Adaptive diagnosis and non-fragile predictive control for HFV engine with non-Gaussian uncertain output

This study presents an adaptive fault estimation and model predictive fault-tolerant control (FTC) for the hypersonic vehicle engine with non-Gaussian uncertain output jet plume. The non-Gaussian probability density function (PDF) describing the plume velocity in a stochastic system is approximated by Type II fuzzy radial basis functions. In the fault observer, the novel prey adaptive estimation method is designed for the valve faults with different amplitudes. Ultimately, this fuzzy-prey fusion adaptive observer shields perturbation and accurately estimates complex faults including incipient and intermittent faults. A predictive tolerant controller compensates for all the faults effects and non-fragile compensation factors of FTC eliminate the perturbation interference, thence the output PDF matches with the expected value. Finally, the more refined internal structure of plume output distribution replaces the local and rough valve position variables, helping this study realizes the hypersonic vehicle engine integrated refine control. Simulation result verifies the effectiveness of the proposed approaches and the superiority compared with the existing method.

Transverse mixing zone under dispersion in porous media: Effects of medium heterogeneity and fluid rheology

The addition of an environmental remediation modifier—polymer solution—to a Newtonian fluid expands the distribution of remediation agents injected in situ into saturated aquifers (affecting plume velocity and deformation), enhancing remediation efficiency. However, the effect of the flow properties of the polymer solution on the macroscopic transverse dispersion remains poorly understood. In this work, a transparent thin-layer two-dimensional sandbox was constructed to simulate the aquifer, and the transverse distribution range of colored solute—permanganate solution and viscous shear-thinning fluid (permanganate solution + xanthan gum)—was captured in real-time by a camera device during transport in porous media. The boundary dispersion coefficient was obtained by fitting a breakthrough curve of the boundary concentration, while the overall plume dispersion coefficient was determined via image moment analysis. The effects of fluid rheology and heterogeneity on the transverse mixing of the plume were analyzed, and the mechanism of viscoelasticity-induced transverse dispersion and mixing enhancement was summarized. The results indicated that the anisotropic stress generated by polymer fluid deformation at high water velocity increased the fluctuation and transverse distribution of the plume, while higher-viscosity polymers increased the initial extrusion swelling and additional compressive stress, covering a larger area. Xanthan gum enhanced the transverse distribution of the plume mainly through initial injection-extrusion expansion effect, viscoelastic stability of the post-injection part, and streamline crossing attributed to elastic turbulence. This study also verified that the shear-thinning fluid enhanced the effect of transverse dispersion and mixing under heterogeneous conditions, providing insights applicable to groundwater remediation.

Lab-scale electrostatic droplet collection from a fog plume with droplet evaporation

The electrostatic droplet collection shows a great potential in harvesting water from fog. However, how and to what extent the droplet evaporation affects the droplet collection efficiency is unclear, which is a key problem to promote the industrial application of the electrostatic fog collection technology. A lab-scale electrostatic fog plume collector was proposed and a numerical model was developed to take the droplet evaporation into account. Experimental and numerical results demonstrated that the fluid transport process in the electrostatic device can be numerically predicted with reasonable accuracy. The ionic wind generated by the corona discharge inhibits the droplet dispersion, which aids the droplet collection. The water vapor mass fraction difference between the fog plume and the ambient air was proposed as the indicator of the droplet evaporation degree. It was found that the droplet collection efficiency decreases with the increasing water vapor mass fraction difference in an exponential law. Furthermore, the droplet collection efficiency loss caused by the droplet evaporation enhances with the decreasing droplet mass concentration in the plume and a loss of 85% occurs when the droplet mass concentration is 6 g/m3. The droplet collection efficiency decreases with the increasing fog plume velocity and a droplet collection efficiency loss of 28%∼43% exists when the plume velocity ranges from 1.3 to 5 m/s.

Fast vacuum plume prediction using a convolutional neural networks-based direct simulation Monte Carlo method

The vacuum plume, which can incur impingement forces, heat fluxes, and contaminations on the spacecraft, has been a vital issue in space missions such as lunar landings. The direct simulation Monte Carlo (DSMC) method is generally used to simulate the vacuum plume. However, DSMC is a particle simulation, and thus, it is very time-consuming, making it impossible to achieve real-time analysis during lunar landings. Motivated by this tricky issue, we explore the feasibility of deep learning to predict the vacuum plume using convolutional neural networks (CNN). In the study, a CNN-based DSMC method (CNN-DSMC) is proposed. The dataset is obtained by the DSMC simulation. The inputs of CNN-DSMC are the shape information and the boundary conditions, which are transformed into the signed distance function (SDF) and identifier matrix (IM), respectively. In particular, a shock-based partitioned method is developed to construct IM to suit the complex flow field with the shock wave. Finally, a vacuum plume velocity field is predicted using the proposed CNN-DSMC, and the prediction of CNN-DSMC is well consistent with DSMC results. Most importantly, compared with the traditional DSMC, the speedup of CNN-DSMC can be up to 4 orders of magnitude, suggesting that CNN-DSMC is a promising method for real-time analysis during lunar landings.

Modeling of abrasive waterjet generated kerf on the top layer of a multi-layered structure

Abrasive waterjet (AWJ) is an effective tool for manufacturing parts from multi-layered structures (MLSs) due to its capability in machining a wide range of materials. However, the challenge in employing AWJ in producing the desired kerf geometry in MLS can be attributed to the complex nature of the jet's interaction with multiple layers that possess different material properties. Hence, a model that captures the interaction of the jet with MLS, and predicts the whole kerf geometry is required to gain control over the kerf quality. On the other hand, the kerf generated in a layer is affected by the presence of preceding-/following- layers. In this context, it is essential to develop a comprehensive model for the prediction of kerf profile during the penetration of the jet in each layer. Although, several models exist to predict the process response (erosion depth, top ( w t ), and bottom kerf width ( w b ), kerf taper), very limited models available on kerf profile prediction. Further, neglecting the actual jet characteristics limits their ability to predict accurately. By considering the above, this work proposes a model for the prediction of the kerf geometry (profile and characteristics) in a single layer of MLS along with its kerf characteristics apart from considering the non-linearities, such as jet characteristics and the effects of AWJ process parameters . A discretized form of the jet, abrasives mass flow distribution, and their velocity in the jet plume to realize a more realistic model for predicting kerf geometry. Further, a new parameter, ' depth of damaged region ’ was defined towards realizing the w t . The model was evaluated by comparing the kerf geometry formed on mild steel (MS) and aluminum (Al) materials by using root mean square and mean absolute error. The proposed model was found to predict the kerf geometry accurately. • First model to predict AWJ generated kerf profile considering abrasive particle velocity profile and mass flow rate distribution. • Development of analytical model to accurately predict the complete kerf profile in a single layer cut by AWJs. • Erosion theories combined with discretization approach in the development of model. • Effective representation of the top kerf width in different materials based on depth of damaged region.