scholarly journals Particle Entrainment and Deposition Scenario in Sublayer Region of Variable Area Conduit

2020 ◽  
Vol 162 ◽  
pp. 03006
Author(s):  
Esam Jassim
Keyword(s):  
Particle Size ◽  
Flow Velocity ◽  
Particle Deposition ◽  
Particle Energy ◽  
Adhesion Energy ◽  
Low Flow ◽  
Threshold Velocity ◽  
Fate Decision ◽  
The Impact ◽  
Aggregation Phenomena

The study presents the particle deposition and aggregation phenomena by introducing new parameter called Particle Deposition Number PDN, defined as the ratio of the particle instantaneous velocity to its capturing value. The particle capture or rebound fate will decide from knowing such number. The study employed new scheme of particle deposition in the sublayer region which includes balancing of four forces. Moreover, the bouncing model is also considered for particle fate decision. The study examines the variation of particle velocity at varying area tube and the critical velocity in which particle will tend to stick if its velocity is lower than the threshold limit. The results show that threshold velocity is exponentially decreased with the increment in the particle size. Capturing of particles is shown to be enhanced as the conduit converges due to increasing in the PDN. The analysis of the deposition also investigates the impact of the particle size on the PDN. At low flow velocity, the NDP has V-shaped trend as particle size increases. However, veering toward constant PDN value has occurred as the flow velocity augmented. Finally, small sized particles experience rebound due to the prevailing of the particle impact energy over the adhesion energy before impacting with the surface. The dissipation in the particle energy during impaction causes large sized particle to loose greater amount of energy compare to small sized one, resulting in domination of the adhesion part, which leads to deposition on the surface.

scholarly journals A mechanistic framework for a priori pharmacokinetic predictions of orally inhaled drugs

2020 ◽  
Vol 16 (12) ◽  
pp. e1008466
Author(s):  
Niklas Hartung ◽  
Jens Markus Borghardt
Keyword(s):  
Particle Size ◽  
Particle Deposition ◽  
Mechanistic Model ◽  
A Priori ◽  
Systemic Exposure ◽  
Drug Dissolution ◽  
Mathematical Framework ◽  
Inhaled Drugs ◽  
Optimal Drug ◽  
The Impact

The fate of orally inhaled drugs is determined by pulmonary pharmacokinetic processes such as particle deposition, pulmonary drug dissolution, and mucociliary clearance. Even though each single process has been systematically investigated, a quantitative understanding on the interaction of processes remains limited and therefore identifying optimal drug and formulation characteristics for orally inhaled drugs is still challenging. To investigate this complex interplay, the pulmonary processes can be integrated into mathematical models. However, existing modeling attempts considerably simplify these processes or are not systematically evaluated against (clinical) data. In this work, we developed a mathematical framework based on physiologically-structured population equations to integrate all relevant pulmonary processes mechanistically. A tailored numerical resolution strategy was chosen and the mechanistic model was evaluated systematically against data from different clinical studies. Without adapting the mechanistic model or estimating kinetic parameters based on individual study data, the developed model was able to predict simultaneously (i) lung retention profiles of inhaled insoluble particles, (ii) particle size-dependent pharmacokinetics of inhaled monodisperse particles, (iii) pharmacokinetic differences between inhaled fluticasone propionate and budesonide, as well as (iv) pharmacokinetic differences between healthy volunteers and asthmatic patients. Finally, to identify the most impactful optimization criteria for orally inhaled drugs, the developed mechanistic model was applied to investigate the impact of input parameters on both the pulmonary and systemic exposure. Interestingly, the solubility of the inhaled drug did not have any relevant impact on the local and systemic pharmacokinetics. Instead, the pulmonary dissolution rate, the particle size, the tissue affinity, and the systemic clearance were the most impactful potential optimization parameters. In the future, the developed prediction framework should be considered a powerful tool for identifying optimal drug and formulation characteristics.

Effect of Particle Size Distribution on the Deep-Bed Capture Efficiency of an Exhaust Particulate Filter

2015 ◽  
Vol 137 (10) ◽  
Author(s):  
Sandeep Viswanathan ◽  
David Rothamer ◽  
Stephen Sakai ◽  
Mitchell Hageman ◽  
David Foster ◽  
...  
Keyword(s):  
Particle Size ◽  
Particle Deposition ◽  
Operating Conditions ◽  
Particulate Filter ◽  
Particulate Emissions ◽  
Flow Area ◽  
Wall Area ◽  
Filter Loading ◽  
Particle Sizer ◽  
The Impact

The exhaust filtration analysis system (EFA) developed at the University of Wisconsin–Madison was used to perform microscale filtration experiments on cordierite filter samples using particulate matter (PM) generated by a spark ignition direct injection (SIDI) engine fueled with gasoline. A scanning mobility particle sizer (SMPS) was used to characterize running conditions with four distinct particle size distributions (PSDs). The distributions selected differed in the relative number of accumulation versus nucleation mode particles. The SMPS and an engine exhaust particle sizer (EEPS) were used to simultaneously measure the PSD downstream of the EFA and the real-time particulate emissions from the SIDI engine to determine the evolution of filtration efficiency (FE) during filter loading. Cordierite filter samples with properties representative of diesel particulate filters (DPFs) were loaded with PM from the different engine operating conditions. The results were compared to understand the impact of PSD on filtration performance as well as the role of accumulation mode particles on the diffusion capture of PM. The most penetrating particle size (MPPS) was observed to decrease as a result of particle deposition within the filter substrate. In the absence of a soot cake, the penetration of particles smaller than 70 nm was seen to gradually increase with time, potentially due to increased velocities in the filter as flow area reduces during filter loading, or due to decreasing wall area for capture of particles by diffusion. Particle re-entrainment was not observed for any of the operating conditions.

Effect of Particle Size Distribution on the Deep-Bed Capture Efficiency of an Exhaust Particulate Filter

2014 ◽  
Author(s):  
Sandeep Viswanathan ◽  
Stephen S. Sakai ◽  
Mitchell Hageman ◽  
David E. Foster ◽  
Todd Fansler ◽  
...  
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Particle Deposition ◽  
Operating Conditions ◽  
Particulate Filter ◽  
Particulate Emissions ◽  
Filter Loading ◽  
Particle Sizer ◽  
The Impact

The exhaust filtration analysis system (EFA) developed at the University of Wisconsin – Madison was used to perform micro-scale filtration experiments on cordierite filter samples using particulate matter (PM) generated by a spark-ignition direct injection (SIDI) engine fueled with gasoline. A scanning mobility particle sizer (SMPS) was used to characterize running conditions with four distinct particle size distributions (PSDs). The distributions selected differed in the relative number of accumulation versus nucleation mode particles. The SMPS and an engine exhaust particle sizer (EEPS) were used to simultaneously measure the PSD downstream of the EFA and the real-time particulate emissions from the SIDI engine to determine the evolution of filtration efficiency during filter loading. Cordierite filter samples with properties representative of diesel particulate filters (DPFs) were loaded with PM from the different engine operating conditions. The results were compared to understand the impact of particle size distribution on filtration performance as well as the role of accumulation mode particles on the diffusion capture of PM. The most penetrating particle size (MPPS) was observed to decrease as a result of particle deposition within the filter substrate. In the absence of a soot cake, the penetration of particles smaller than 70 nm was seen to gradually increase with time, potentially due to increased velocities in the filter as flow area reduces during filter loading, or due to decreasing wall area for capture of particles by diffusion. Particle re-entrainment was not observed for any of the operating conditions.

scholarly journals Aerosol dynamics within and above forest in relation to turbulent transport and dry deposition

2015 ◽  
Vol 15 (14) ◽  
pp. 19367-19403 ◽  
Author(s):  
Ü. Rannik ◽  
L. Zhou ◽  
P. Zhou ◽  
R. Gierens ◽  
I. Mammarella ◽  
...  
Keyword(s):  
Particle Size ◽  
Size Distribution ◽  
Time Scales ◽  
Atmospheric Chemistry ◽  
Dry Deposition ◽  
Particle Deposition ◽  
Vertical Transport ◽  
Forest Site ◽  
Aerosol Dynamics ◽  
The Impact

Abstract. One dimensional atmospheric boundary layer (ABL) model coupled with detailed atmospheric chemistry and aerosol dynamical model, the model SOSAA, was used to predict the ABL and detailed aerosol population (characterized by the number size distribution) time evolution. The model was applied over a period of ten days in May 2013 for a pine forest site in southern Finland. The period was characterized by frequent new particle formation events and simultaneous intensive aerosol transformation. Throughout this study we refer to nucleation, condensational growth and coagulation as aerosol dynamical processes, i.e. the processes that govern the particle size distribution evolution. The aim of the study was to analyze and quantify the role of aerosol and ABL dynamics in vertical transport of aerosols. It was of particular interest to what extent the fluxes above canopy deviate due to above mentioned processes from the particle dry deposition on the canopy foliage. The model simulations revealed that the particle concentration change due to aerosol dynamics can frequently exceed the effect of particle deposition even an order of magnitude or more. The impact is however strongly dependent on particle size and time. In spite of the fact that the time scale of turbulent transfer inside canopy is much smaller than the time scales of aerosol dynamics and dry deposition, letting to assume well mixed properties of air, the fluxes at the canopy top frequently deviate from deposition inside forest. This is due to transformation of aerosol concentration throughout the ABL and resulting complicated pattern of vertical transport. Therefore we argue that the comparison of time scales of aerosol dynamics and deposition defined for the processes below the flux measurement level do not unambiguously describe the importance of aerosol dynamics for vertical transport within canopy. We conclude that under dynamical conditions the micrometeorological particle flux measurements such as performed by the eddy covariance technique do not generally represent the dry deposition. The deviation can be systematic for certain size ranges so that the conclusion applies also to time averaged particle fluxes.

Numerical Investigation of Deposition Characteristics of Solid CO2 During Choked Flow for CO2 Pipelines

2016 ◽  
Author(s):  
Lin Teng ◽  
Yuxing Li ◽  
Hui Han ◽  
Pengfei Zhao ◽  
Datong Zhang
Keyword(s):  
Particle Size ◽  
Flow Velocity ◽  
Particle Deposition ◽  
Transport Model ◽  
Fluid Dynamic ◽  
Flow Characteristics ◽  
Stokes Number ◽  
Sudden Expansion ◽  
Choked Flow ◽  
Tracking Model

Choke valves are applied to control the pressure in CO2 pipeline. However, the temperature of fluid would drop rapidly because of Joule-Thomson cooling (JTC), which may cause solid CO2 generate and block the pipe. In this work, a three-dimensional Computational Fluid Dynamic (CFD) model, using the Lagrangian method, Reynold’s Stress Transport model (RSM) for turbulence and stochastic tracking model (STM) for particle trajectory, was developed to predict the gas-solid CO2 flow and deposition characteristics downstream pipeline. The model predictions were in good agreement with the experimental data published in the literature. The effects of particle size, flow velocity and pipeline diameter on the fluid-particle flow characteristics were examined. Results showed that the increase in the flow velocity would cause a decrease in particle deposition ratio and there existed the critical particle size that caused the deposition ratio maximum for each velocity. The paper also presents the effects of particle motion on different deposition regions. Moreover, the main deposition region (the sudden expansion region) is the easy to be blocked by the particles. With the increase in pipeline diameter, the particle deposition ratio was decreasing. In addition, it was recommended for Stokes number to avoid 3-8 St.

scholarly journals Determination of erosion equation factors of AISI1020 by experimental data

2020 ◽  
Vol 21 (2) ◽  
pp. 201
Author(s):  
Mehdi Akhondizadeh ◽  
Nader Afkhami
Keyword(s):  
Experimental Data ◽  
Particle Size ◽  
Flow Velocity ◽  
Incidence Angle ◽  
Erosive Wear ◽  
Wear Test ◽  
Impact Angle ◽  
Test Machine ◽  
Erosion Equation ◽  
The Impact

Erosive wear is material removal due to the impingement of granular flow. In the present work, the effects of influencing parameters including flow velocity, incidence angle and grain size on erosive behavior of AISI1020 subjected to a flow of SiC particles has been investigated by employing an erosion wear test machine. The experiments have been performed at the different values of impact angle, flow velocity and particle size. Two tests have been performed for every set of conditions and the average of them has been presented. Results showed that the erosive wear maximizes at the impact angles of 30° and 45°. The flow of small particles resulted in more wear contrast to the large particles. Results also indicated that the influence of flow velocity was higher than the influence of impact angle and particle size. It means that minimizing the flow velocity results in more efficient results to reduce erosion. Moreover, the experimental data were used to determine appropriate coefficients for using in an erosion equation given by literature. New factors gave erosion evaluations which had appropriate accordance with the experimental data.

Flow and Deposition Characteristics Following Chokes for Pressurized CO2 Pipelines

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
Lin Teng ◽  
Yuxing Li ◽  
Hui Han ◽  
Pengfei Zhao ◽  
Datong Zhang
Keyword(s):  
Particle Size ◽  
Flow Velocity ◽  
Particle Deposition ◽  
Transport Model ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Stokes Number ◽  
Sudden Expansion ◽  
Tracking Model ◽  
Good Agreement

The relieving system using the choke valve is applied to control the pressure in CO2 pipeline. However, the temperature of fluid would drop rapidly because of Joule–Thomson cooling (JTC), which may cause solid CO2 form and block the pipe. A three-dimensional (3D) computational fluid dynamic (CFD) model considering the phase transition and turbulence was developed to predict the fluid-particle flow and deposition characteristics. The Lagrangian method, Reynold's stress transport model (RSM) for turbulence, and stochastic tracking model (STM) were used. The results show that the model predictions were in good agreement with the experimental data published. The effects of particle size, flow velocity, and pipeline diameter were analyzed. It was found that the increase of the flow velocity would cause the decrease of particle deposition ratio and there existed the critical particle size that causes the deposition ratio maximum. It also presents the four types of particle motions corresponding to the four deposition regions. Moreover, the sudden expansion region is the easiest to be blocked by the particles. In addition, the Stokes number had an effect on the deposition ratio and it was recommended for Stokes number to avoid 3–8 St.

scholarly journals Seasonal streamflow forecasting by conditioning climatology with precipitation indices

2017 ◽  
Vol 21 (3) ◽  
pp. 1573-1591 ◽  
Author(s):  
Louise Crochemore ◽  
Maria-Helena Ramos ◽  
Florian Pappenberger ◽  
Charles Perrin
Keyword(s):  
Long Range ◽  
Precipitation Forecast ◽  
Low Flow ◽  
Drought Risk ◽  
Streamflow Forecasting ◽  
Streamflow Forecasts ◽  
Precipitation Indices ◽  
Seasonal Streamflow ◽  
Prediction Approach ◽  
The Impact

Abstract. Many fields, such as drought-risk assessment or reservoir management, can benefit from long-range streamflow forecasts. Climatology has long been used in long-range streamflow forecasting. Conditioning methods have been proposed to select or weight relevant historical time series from climatology. They are often based on general circulation model (GCM) outputs that are specific to the forecast date due to the initialisation of GCMs on current conditions. This study investigates the impact of conditioning methods on the performance of seasonal streamflow forecasts. Four conditioning statistics based on seasonal forecasts of cumulative precipitation and the standardised precipitation index were used to select relevant traces within historical streamflows and precipitation respectively. This resulted in eight conditioned streamflow forecast scenarios. These scenarios were compared to the climatology of historical streamflows, the ensemble streamflow prediction approach and the streamflow forecasts obtained from ECMWF System 4 precipitation forecasts. The impact of conditioning was assessed in terms of forecast sharpness (spread), reliability, overall performance and low-flow event detection. Results showed that conditioning past observations on seasonal precipitation indices generally improves forecast sharpness, but may reduce reliability, with respect to climatology. Conversely, conditioned ensembles were more reliable but less sharp than streamflow forecasts derived from System 4 precipitation. Forecast attributes from conditioned and unconditioned ensembles are illustrated for a case of drought-risk forecasting: the 2003 drought in France. In the case of low-flow forecasting, conditioning results in ensembles that can better assess weekly deficit volumes and durations over a wider range of lead times.

scholarly journals Waterfall Algorithm as a tool of investigation the geometrical features of granular porous media

2021 ◽  
Author(s):  
Wojciech Sobieski
Keyword(s):  
Particle Size ◽  
Porous Media ◽  
Lattice Boltzmann ◽  
Granular Media ◽  
Density Ratio ◽  
Geometrical Features ◽  
Granular Porous Media ◽  
Collision Density ◽  
Boltzmann Method ◽  
The Impact

AbstractThe paper describes the so-called Waterfall Algorithm, which may be used to calculate a set of parameters characterising the spatial structure of granular porous media, such as shift ratio, collision density ratio, consolidation ratio, path length and minimum tortuosity. The study is performed for 1800 different two-dimensional random pore structures. In each geometry, 100 individual paths are calculated. The impact of porosity and the particle size on the above-mentioned parameters is investigated. It was stated in the paper, that the minimum tortuosity calculated by the Waterfall Algorithm cannot be used directly as a representative tortuosity of pore channels in the Kozeny or the Carman meaning. However, it may be used indirect by making the assumption that a unambiguous relationship between the representative tortuosity and the minimum tortuosity exists. It was also stated, that the new parameters defined in the present study are sensitive on the porosity and the particle size and may be therefore applied as indicators of the geometry structure of granular media. The Waterfall Algorithm is compared with other methods of determining the tortuosity: A-Star Algorithm, Path Searching Algorithm, Random Walk technique, Path Tracking Method and the methodology of calculating the hydraulic tortuosity based on the Lattice Boltzmann Method. A very short calculation time is the main advantage of the Waterfall Algorithm, what meant, that it may be applied in a very large granular porous media.

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