Separated and reattached turbulent flows induced by two-dimensional forward-backward-facing steps with different streamwise lengths submerged in a thick turbulent boundary layer are investigated using a time-resolved particle image velocimetry. The examined aspect ratios of the step range from 1 to 8, and the Reynolds number based on the free-stream velocity and step height is 13 200. The thickness of the oncoming turbulent boundary layer is 6.5 times the step height. The effects of varying aspect ratio of the steps on the mean flow, Reynolds stresses, triple correlations and unsteadiness of turbulent separation bubbles are studied. It was found that the mean flow reattaches over the step for forward-backward facing steps with aspect ratios of 2 and higher. The temporal variation of the first proper orthogonal decomposition (POD) mode and reverse flow area, which is used to examine the flapping motion of separation bubble, shows remarkable synchronization.
{"title":"Effects of Streamwise Aspect Ratio on Turbulent Flows Over Forward-Backward Facing Steps","authors":"H. Chalmers, Xingjun Fang, M. Tachie","doi":"10.1115/fedsm2020-20263","DOIUrl":"https://doi.org/10.1115/fedsm2020-20263","url":null,"abstract":"\u0000 Separated and reattached turbulent flows induced by two-dimensional forward-backward-facing steps with different streamwise lengths submerged in a thick turbulent boundary layer are investigated using a time-resolved particle image velocimetry. The examined aspect ratios of the step range from 1 to 8, and the Reynolds number based on the free-stream velocity and step height is 13 200. The thickness of the oncoming turbulent boundary layer is 6.5 times the step height. The effects of varying aspect ratio of the steps on the mean flow, Reynolds stresses, triple correlations and unsteadiness of turbulent separation bubbles are studied. It was found that the mean flow reattaches over the step for forward-backward facing steps with aspect ratios of 2 and higher. The temporal variation of the first proper orthogonal decomposition (POD) mode and reverse flow area, which is used to examine the flapping motion of separation bubble, shows remarkable synchronization.","PeriodicalId":333138,"journal":{"name":"Volume 2: Fluid Mechanics; Multiphase Flows","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-07-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130647862","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Farokhipour, Z. Mansoori, M. Saffar‐Avval, S. Shirazi, G. Ahmadi
In many industrial applications, gas-liquid-particle three-phase flows are observed. Predicting erosion damage in this type of flow is a challenging issue, and so many factors, such as the liquid film behavior have significant effects on the erosion rate. In the present study, the Eulerian-Lagrangian approach was implemented to study the process of sand particle erosion in elbows with different bend angles. For this purpose, gas and liquid phases under annular flow conditions were introduced at the pipe inlet, and the volume of fluid (VOF) method was employed to solve the governing equations. For evaluating the erosion rate, the Det Norske Veritas (DNV) model was applied. The predicted erosion results for the bend angles of 30°, 60° and 90° at different orientations were compared with those of the two-phase gas-particle flows. The simulation results indicated that for gas-liquid-particle flow, the behavior of film thickness in the bend plays a major role on the particle impact velocity and the corresponding erosion rates. By comparing the impact characteristics for gas and liquid superficial velocities of 40 and 0.4 m/s, respectively, in the 90° elbow, it was found that the impact velocities for gas-particle and gas-liquid-particle flows at the erosion hotspot are 38 and 14 m/s, respectively. In addition, among the studied geometries, the 30° elbow is the most erosion-resistant bend angle configuration among those studied for both two- and three-phase flows.
{"title":"CFD Evaluation of Bend Angle Effects on Sand Particle Erosion in Multiphase Flows","authors":"A. Farokhipour, Z. Mansoori, M. Saffar‐Avval, S. Shirazi, G. Ahmadi","doi":"10.1115/fedsm2020-20069","DOIUrl":"https://doi.org/10.1115/fedsm2020-20069","url":null,"abstract":"\u0000 In many industrial applications, gas-liquid-particle three-phase flows are observed. Predicting erosion damage in this type of flow is a challenging issue, and so many factors, such as the liquid film behavior have significant effects on the erosion rate. In the present study, the Eulerian-Lagrangian approach was implemented to study the process of sand particle erosion in elbows with different bend angles. For this purpose, gas and liquid phases under annular flow conditions were introduced at the pipe inlet, and the volume of fluid (VOF) method was employed to solve the governing equations. For evaluating the erosion rate, the Det Norske Veritas (DNV) model was applied. The predicted erosion results for the bend angles of 30°, 60° and 90° at different orientations were compared with those of the two-phase gas-particle flows. The simulation results indicated that for gas-liquid-particle flow, the behavior of film thickness in the bend plays a major role on the particle impact velocity and the corresponding erosion rates. By comparing the impact characteristics for gas and liquid superficial velocities of 40 and 0.4 m/s, respectively, in the 90° elbow, it was found that the impact velocities for gas-particle and gas-liquid-particle flows at the erosion hotspot are 38 and 14 m/s, respectively. In addition, among the studied geometries, the 30° elbow is the most erosion-resistant bend angle configuration among those studied for both two- and three-phase flows.","PeriodicalId":333138,"journal":{"name":"Volume 2: Fluid Mechanics; Multiphase Flows","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-07-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123801028","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Solid-liquid flow is studied in an open channel with a mobile bed at the condition of intense transport of solids. It is flow of high-concentrated mixture of coarse sediment and water over a plane surface of the bed eroded due to high bed shear. In the flow, solid particles are non-uniformly distributed across the flow depth. The flow develops a transport layer, adjacent to the the top of the bed, in which transported particles interact with each other. Results are presented of experimental investigations of the sediment-laden open-channel flow in a recirculating titling flume. The experiments included measurements (using ultrasonic techniques) of the distribution of solids velocity across the transport layer. The related distribution of solids concentration was deduced from the measured distribution of velocity and from other measured flow quantities. Since recently, a direct measurement of the solids distribution across the transport layer has been added to the experiments using a measuring technique svideo camera and a laser sheet. This work discusses results of combined measurements of the distributions of solids concentration and velocity in steady uniform turbulent flow for two lightweight solids fractions and various flow conditions (a broad range of the bed Shields parameter, discharge of solids, discharge of mixture, and the longitudinal slope of the bed). Furthermore, the camera-based measuring method and the deducing method for a determination of solids distribution are discussed and their results compared to show a good agreement in a majority of the test runs. The experimental results are compared with predictions of a recently developed bed-load transport model. Among other outputs, the model predicts the position of the top of the transport layer and the local velocity of sediment particles at this position. The presented model predictions agree well with experimental results based on the measured distibutions.
{"title":"Solids Distribution in Sediment-Laden Open-Channel Flow: Experiment and Prediction","authors":"V. Matoušek, J. Krupička, T. Picek, Š. Zrostlík","doi":"10.1115/fedsm2020-20198","DOIUrl":"https://doi.org/10.1115/fedsm2020-20198","url":null,"abstract":"\u0000 Solid-liquid flow is studied in an open channel with a mobile bed at the condition of intense transport of solids. It is flow of high-concentrated mixture of coarse sediment and water over a plane surface of the bed eroded due to high bed shear. In the flow, solid particles are non-uniformly distributed across the flow depth. The flow develops a transport layer, adjacent to the the top of the bed, in which transported particles interact with each other.\u0000 Results are presented of experimental investigations of the sediment-laden open-channel flow in a recirculating titling flume. The experiments included measurements (using ultrasonic techniques) of the distribution of solids velocity across the transport layer. The related distribution of solids concentration was deduced from the measured distribution of velocity and from other measured flow quantities. Since recently, a direct measurement of the solids distribution across the transport layer has been added to the experiments using a measuring technique svideo camera and a laser sheet.\u0000 This work discusses results of combined measurements of the distributions of solids concentration and velocity in steady uniform turbulent flow for two lightweight solids fractions and various flow conditions (a broad range of the bed Shields parameter, discharge of solids, discharge of mixture, and the longitudinal slope of the bed). Furthermore, the camera-based measuring method and the deducing method for a determination of solids distribution are discussed and their results compared to show a good agreement in a majority of the test runs.\u0000 The experimental results are compared with predictions of a recently developed bed-load transport model. Among other outputs, the model predicts the position of the top of the transport layer and the local velocity of sediment particles at this position. The presented model predictions agree well with experimental results based on the measured distibutions.","PeriodicalId":333138,"journal":{"name":"Volume 2: Fluid Mechanics; Multiphase Flows","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-07-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126492543","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hot-wire measurements were taken in the wake of ten finite length circular cylinders, six of which were also tapered, in a uniform flow in a low speed wind tunnel. The Reynolds number based on mean cylinder diameter ranged from 2100 ≤ Re ≤ 5500, the aspect ratio (AR) of the cylinders varied from 16 ≤ AR ≤ 64, and the taper ratio (RT) varied from 21.3 ≤ RT ≤ 96. The vortex shedding along the spans of the cylinders coalesced into discrete cells, the range of Strouhal numbers and the number of cells being a function of the cylinder aspect ratio and taper ratio. It was found that the number of discrete cells is linearly related to a cylinder geometry ratio (CGR) defined as CGR = AR(1 + AR/RT).
{"title":"Cellular Vortex Shedding From Linearly Tapered Finite Cylinders","authors":"D. M. Rooney, J. Vaccaro, R. Smijtink","doi":"10.1115/fedsm2020-20043","DOIUrl":"https://doi.org/10.1115/fedsm2020-20043","url":null,"abstract":"\u0000 Hot-wire measurements were taken in the wake of ten finite length circular cylinders, six of which were also tapered, in a uniform flow in a low speed wind tunnel. The Reynolds number based on mean cylinder diameter ranged from 2100 ≤ Re ≤ 5500, the aspect ratio (AR) of the cylinders varied from 16 ≤ AR ≤ 64, and the taper ratio (RT) varied from 21.3 ≤ RT ≤ 96. The vortex shedding along the spans of the cylinders coalesced into discrete cells, the range of Strouhal numbers and the number of cells being a function of the cylinder aspect ratio and taper ratio. It was found that the number of discrete cells is linearly related to a cylinder geometry ratio (CGR) defined as CGR = AR(1 + AR/RT).","PeriodicalId":333138,"journal":{"name":"Volume 2: Fluid Mechanics; Multiphase Flows","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-07-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125306073","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Microfluidic delivery systems have been employed to facilitate cell seeding procedures in drug development for personalized medicine for cancer patients. Despite of the high-throughput nature and potential impact on clinical outcomes of these systems, the efficiency in cell trapping remains a challenge in the operation. Droplet-based microfluidics became one of the solutions due to the large size of the cell-enclosing droplets and their interfacial properties. This study is focused on the motion of the cell-enclosing droplet in a constricted return bends that help to restrict the release of the cells while maintaining the high-throughput nature of the device. In this preliminary study, a three-dimensional boundary element method is used to predict droplet shape, deformation and migration velocity under the influence of various fluid properties and operational conditions. A variety of channel geometries have been explored as well. The resulting computational framework will be used to guide the design of a droplet-based microfluidic delivery system for cell seeding in 3D tumor spheroid arrays.
{"title":"Droplet Dynamics in Constricted Return Bends of Microfluidic Channels","authors":"Julie A. Melbye, Yechun Wang","doi":"10.1115/fedsm2020-20406","DOIUrl":"https://doi.org/10.1115/fedsm2020-20406","url":null,"abstract":"\u0000 Microfluidic delivery systems have been employed to facilitate cell seeding procedures in drug development for personalized medicine for cancer patients. Despite of the high-throughput nature and potential impact on clinical outcomes of these systems, the efficiency in cell trapping remains a challenge in the operation. Droplet-based microfluidics became one of the solutions due to the large size of the cell-enclosing droplets and their interfacial properties. This study is focused on the motion of the cell-enclosing droplet in a constricted return bends that help to restrict the release of the cells while maintaining the high-throughput nature of the device. In this preliminary study, a three-dimensional boundary element method is used to predict droplet shape, deformation and migration velocity under the influence of various fluid properties and operational conditions. A variety of channel geometries have been explored as well. The resulting computational framework will be used to guide the design of a droplet-based microfluidic delivery system for cell seeding in 3D tumor spheroid arrays.","PeriodicalId":333138,"journal":{"name":"Volume 2: Fluid Mechanics; Multiphase Flows","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-07-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124385304","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Thomas G. Shepard, John E. Wentz, T. Bender, Derek Olmschenk, Alex Gutenberg
Flow conduits made via additive manufacturing, commonly referred to as 3-D printing, are of increasing interest for a variety of industrial applications due to the ability to create unique and conformal flow paths that would not be possible with other fabrication techniques. Fused filament fabrication (FFF) is an additive manufacturing technique that is seeing new interest in the creation of internal flow channels with its ability to print high-temperature polymers and soluble supports. Printing parameter choices in the FFF printing process result in surfaces that can have significant profile differences that may significantly impact the flow characteristics within the conduits. In this study, two print parameters were experimentally studied for turbulent water flow through circular pipes created by fused filament fabrication out of acrylonitrile butadiene styrene (ABS). The print layer orientation relative to the flow was investigated for printing layers parallel, perpendicular, and at 45 degrees from the flow axis. Layer thickness were varied from 0.254 mm to 0.330 mm and all channels were created using soluble support structures. Pressure drops were measured for fully developed flow through pipes with an inside diameter of 5 mm and Reynolds numbers up to 62,000. Results are presented in terms of relative pressure drops as well as the wall surface roughness that would lead to such impacts. These flow-determined grain surface roughnesses are then compared against measurements of print surface roughness.
{"title":"Impact of Print Parameters on Pressure Drop in Turbulent Flow Through 3-D Printed Pipes","authors":"Thomas G. Shepard, John E. Wentz, T. Bender, Derek Olmschenk, Alex Gutenberg","doi":"10.1115/fedsm2020-20252","DOIUrl":"https://doi.org/10.1115/fedsm2020-20252","url":null,"abstract":"\u0000 Flow conduits made via additive manufacturing, commonly referred to as 3-D printing, are of increasing interest for a variety of industrial applications due to the ability to create unique and conformal flow paths that would not be possible with other fabrication techniques. Fused filament fabrication (FFF) is an additive manufacturing technique that is seeing new interest in the creation of internal flow channels with its ability to print high-temperature polymers and soluble supports. Printing parameter choices in the FFF printing process result in surfaces that can have significant profile differences that may significantly impact the flow characteristics within the conduits. In this study, two print parameters were experimentally studied for turbulent water flow through circular pipes created by fused filament fabrication out of acrylonitrile butadiene styrene (ABS). The print layer orientation relative to the flow was investigated for printing layers parallel, perpendicular, and at 45 degrees from the flow axis. Layer thickness were varied from 0.254 mm to 0.330 mm and all channels were created using soluble support structures. Pressure drops were measured for fully developed flow through pipes with an inside diameter of 5 mm and Reynolds numbers up to 62,000. Results are presented in terms of relative pressure drops as well as the wall surface roughness that would lead to such impacts. These flow-determined grain surface roughnesses are then compared against measurements of print surface roughness.","PeriodicalId":333138,"journal":{"name":"Volume 2: Fluid Mechanics; Multiphase Flows","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-07-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114628906","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Prichard, W. Strasser, Chad Cherok, Robert Kacinski, A. Lang
In this paper, we use a CFD analysis of a simplified, 2D geometry to study the ability of mako shark denticles to mitigate flow separation. We represent the viscous sublayer below a turbulent boundary layer streak as a Couette flow. Incipient separation is simulated by balancing upper wall velocity and adverse pressure gradient to achieve zero net mass flow, and we add various denticle geometries to study their effects. Each modeled denticle protrudes at an angle from 15° to 85° and sublayer blockage ratio from 0.05 to 0.85. Through variation of fluid properties and boundary conditions, we show that the anti-flow-reversal abilities of a single, bristled shark denticle are independent of Reynolds number, and we investigate the effect of the denticle at cases other than zero net mass flux. Based on these results, we create a new relationship to predict separation inhibition. These conclusions are highly generalizable and represent previously undiscovered universal behavior.
{"title":"Passive Bristling of Shark Skin Scales at the Micro-Level: A Fundamental Viscous Flow Study to Understand the Separation Control Mechanism","authors":"R. Prichard, W. Strasser, Chad Cherok, Robert Kacinski, A. Lang","doi":"10.1115/fedsm2020-20457","DOIUrl":"https://doi.org/10.1115/fedsm2020-20457","url":null,"abstract":"\u0000 In this paper, we use a CFD analysis of a simplified, 2D geometry to study the ability of mako shark denticles to mitigate flow separation. We represent the viscous sublayer below a turbulent boundary layer streak as a Couette flow. Incipient separation is simulated by balancing upper wall velocity and adverse pressure gradient to achieve zero net mass flow, and we add various denticle geometries to study their effects. Each modeled denticle protrudes at an angle from 15° to 85° and sublayer blockage ratio from 0.05 to 0.85. Through variation of fluid properties and boundary conditions, we show that the anti-flow-reversal abilities of a single, bristled shark denticle are independent of Reynolds number, and we investigate the effect of the denticle at cases other than zero net mass flux. Based on these results, we create a new relationship to predict separation inhibition. These conclusions are highly generalizable and represent previously undiscovered universal behavior.","PeriodicalId":333138,"journal":{"name":"Volume 2: Fluid Mechanics; Multiphase Flows","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-07-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130182146","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Surfactant-based, SB fluids exhibit complex rheological behavior due to substantial structural changes caused by the molecules self-assembled colloidal aggregation. Temperature and salinity affect their rheology and flow properties. In this study, both rheological and viscoelastic properties for the optimum concentration, 4%, of Aromox® APA-T viscoelastic surfactant (VES) were investigated using two brine solutions; 2 and 4% KCl and wide range of temperatures (72°F – 200°F). Flow properties were examined using a 1/2-in. straight and coiled tubing (CR = 0.019). The results show that increasing solution salinity promotes formation of rod-like micelles and increases its flexibility. Salinity affects micelles growth and their rheological and viscoelastic behavior is very sensitive to the nature and structure of the added salt. Different molecular structures are formed; spherical micelles occur first and then increased temperature and/or salinity promotes the formation of rod-like micelles. Later, rod-like micelles are aligned in the flow direction and form a large super ordered structure of micellar bundles or aggregates called shear induced structure (SIS). Different structures implies different rheological and flow properties. Likewise, rheology improves with increasing temperature up to 100°F. Further increase in temperature reverses the effects and viscosity decreases. In addition, drag reduction and flow characteristics of SB fluids are improved by the addition of salt and/or increasing temperature up to 100°F. Results obtained are in full agreement with rheological and viscoelastic behavior of SB fluids for both salinity and temperature.
{"title":"Effects of Salinity and Temperature on Rheological and Flow Characteristics of Surfactant-Based Fluids","authors":"A. Kamel, A. Alzahabi","doi":"10.1115/fedsm2020-20025","DOIUrl":"https://doi.org/10.1115/fedsm2020-20025","url":null,"abstract":"\u0000 Surfactant-based, SB fluids exhibit complex rheological behavior due to substantial structural changes caused by the molecules self-assembled colloidal aggregation. Temperature and salinity affect their rheology and flow properties.\u0000 In this study, both rheological and viscoelastic properties for the optimum concentration, 4%, of Aromox® APA-T viscoelastic surfactant (VES) were investigated using two brine solutions; 2 and 4% KCl and wide range of temperatures (72°F – 200°F). Flow properties were examined using a 1/2-in. straight and coiled tubing (CR = 0.019).\u0000 The results show that increasing solution salinity promotes formation of rod-like micelles and increases its flexibility. Salinity affects micelles growth and their rheological and viscoelastic behavior is very sensitive to the nature and structure of the added salt. Different molecular structures are formed; spherical micelles occur first and then increased temperature and/or salinity promotes the formation of rod-like micelles. Later, rod-like micelles are aligned in the flow direction and form a large super ordered structure of micellar bundles or aggregates called shear induced structure (SIS). Different structures implies different rheological and flow properties. Likewise, rheology improves with increasing temperature up to 100°F. Further increase in temperature reverses the effects and viscosity decreases. In addition, drag reduction and flow characteristics of SB fluids are improved by the addition of salt and/or increasing temperature up to 100°F. Results obtained are in full agreement with rheological and viscoelastic behavior of SB fluids for both salinity and temperature.","PeriodicalId":333138,"journal":{"name":"Volume 2: Fluid Mechanics; Multiphase Flows","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-07-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131004510","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study presents the results of a series of numerical simulations for airflow field and particle dispersion and deposition around a mannequin standing inside a ventilated room. A 3-D airway model was constructed from the nostril inlet to the end of 4th lung generation and was integrated into the standing mannequin model in the room. The computational domain included the region around the mannequin and inside the respiratory system. The room was ventilated by a mixing air-conditioning system that supplied air with a speed of 3m/s from a diffuser mounted on the top of the sidewall and exited from a damper mounted at the bottom of the side or front walls. In the first mode, the diffuser and damper were located on the wall in front of the mannequin and in the second mode on the wall at the right side of the mannequin. The mean airflow field inside the room was obtained by solving the Navier-Stokes and continuity equations using the Ansys-Fluent software. The k-ω SST transitional model was employed for turbulence modeling. Then, spherical particles with 5, 10, 20, and 40 μm diameter and unit density were released into the room, and their trajectories were tracked by using the Lagrangian trajectory analysis approach. Aspiration efficiency and deposition of particles for inhalation flow rates of 15 and 30 lit/min were analyzed with the improved discrete random walk (DRW) stochastic model using a user-defined function (UDF) coupled into the Ansys-Fluent discrete phase model. Simulation results for the mean airflow showed the formation of a large recirculation zone inside the room. In the first mode, the main recirculation zone formed behind mannequin that carried the flow streamlines toward the mannequin breathing zone. In the second mode, the recirculation formed in front of the mannequin face that led the streamlines out of the breathing zone. The simulation results for particle inhalation showed that the aspiration efficiency of particles is higher in the first ventilation mode compared to the second mode. Results also showed that the total deposition of particles in the airway passage increases as particle size increases.
{"title":"Particle Transport and Deposition in a Ventilated Room With a Standing Mannequin","authors":"M. Azhdari, M. Tavakol, G. Ahmadi","doi":"10.1115/fedsm2020-20450","DOIUrl":"https://doi.org/10.1115/fedsm2020-20450","url":null,"abstract":"\u0000 This study presents the results of a series of numerical simulations for airflow field and particle dispersion and deposition around a mannequin standing inside a ventilated room. A 3-D airway model was constructed from the nostril inlet to the end of 4th lung generation and was integrated into the standing mannequin model in the room. The computational domain included the region around the mannequin and inside the respiratory system. The room was ventilated by a mixing air-conditioning system that supplied air with a speed of 3m/s from a diffuser mounted on the top of the sidewall and exited from a damper mounted at the bottom of the side or front walls. In the first mode, the diffuser and damper were located on the wall in front of the mannequin and in the second mode on the wall at the right side of the mannequin. The mean airflow field inside the room was obtained by solving the Navier-Stokes and continuity equations using the Ansys-Fluent software. The k-ω SST transitional model was employed for turbulence modeling. Then, spherical particles with 5, 10, 20, and 40 μm diameter and unit density were released into the room, and their trajectories were tracked by using the Lagrangian trajectory analysis approach. Aspiration efficiency and deposition of particles for inhalation flow rates of 15 and 30 lit/min were analyzed with the improved discrete random walk (DRW) stochastic model using a user-defined function (UDF) coupled into the Ansys-Fluent discrete phase model. Simulation results for the mean airflow showed the formation of a large recirculation zone inside the room. In the first mode, the main recirculation zone formed behind mannequin that carried the flow streamlines toward the mannequin breathing zone. In the second mode, the recirculation formed in front of the mannequin face that led the streamlines out of the breathing zone. The simulation results for particle inhalation showed that the aspiration efficiency of particles is higher in the first ventilation mode compared to the second mode. Results also showed that the total deposition of particles in the airway passage increases as particle size increases.","PeriodicalId":333138,"journal":{"name":"Volume 2: Fluid Mechanics; Multiphase Flows","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-07-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128914128","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
F. B. Rajeb, Mohamed Odan, A. Aborig, S. Imtiaz, Yan Zhang, M. Awad, M. A. Rahman
Two-phase flow of gas/Newtonian and gas/non-Newtonian fluid through pipes occurs frequently in the chemical industry as well as in petroleum refining. Extensive experimental and theoretical research has been carried out on these systems in order to better understand their behaviour under different conditions regarding pressure, temperature and mixture concentrations. In this study, experimental apparatuses are used to investigate two-phase flow of gas/liquid systems through pipes. Air is used as the gas in the experiments, while water is used as the Newtonian fluid and Xanthan gum as the non-Newtonian fluid. The objectives of the study are to compare pressure drops when the same gas flows simultaneously with Newtonian and non-Newtonian fluids through tubes. The comparison here is between experimental pressure drops and estimated pressure drops, based on available empirical correlations for gas/Newtonian and gas/non-Newtonian flow. The trend exhibited by the pressure drops in both systems helps us to better understand the relationship between mixture flow pressure drops in Newtonian and non-Newtonian fluids and thereby develop a new experimental model. The tube diameter for the flow loop is 3/4 inch and the flow type ranges from transient to turbulent.
{"title":"Experimental Comparison of Newtonian and Non-Newtonian Multiphase Flow in Horizontal Pipes","authors":"F. B. Rajeb, Mohamed Odan, A. Aborig, S. Imtiaz, Yan Zhang, M. Awad, M. A. Rahman","doi":"10.1115/fedsm2020-20236","DOIUrl":"https://doi.org/10.1115/fedsm2020-20236","url":null,"abstract":"\u0000 Two-phase flow of gas/Newtonian and gas/non-Newtonian fluid through pipes occurs frequently in the chemical industry as well as in petroleum refining. Extensive experimental and theoretical research has been carried out on these systems in order to better understand their behaviour under different conditions regarding pressure, temperature and mixture concentrations. In this study, experimental apparatuses are used to investigate two-phase flow of gas/liquid systems through pipes. Air is used as the gas in the experiments, while water is used as the Newtonian fluid and Xanthan gum as the non-Newtonian fluid. The objectives of the study are to compare pressure drops when the same gas flows simultaneously with Newtonian and non-Newtonian fluids through tubes. The comparison here is between experimental pressure drops and estimated pressure drops, based on available empirical correlations for gas/Newtonian and gas/non-Newtonian flow. The trend exhibited by the pressure drops in both systems helps us to better understand the relationship between mixture flow pressure drops in Newtonian and non-Newtonian fluids and thereby develop a new experimental model. The tube diameter for the flow loop is 3/4 inch and the flow type ranges from transient to turbulent.","PeriodicalId":333138,"journal":{"name":"Volume 2: Fluid Mechanics; Multiphase Flows","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-07-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134476730","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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