Pub Date : 2019-11-20DOI: 10.1115/ajkfluids2019-5151
Hiroki Kurahara, K. Ando
We experimentally study the effects of viscosity on laser-induced shockwave in glycerol-water solution. A shockwave is generated through rapid expansion of plasma, which is induced by focusing a 6 ns pulse laser (532 nm) of energy fixed at 1.66 ± 0.22 mJ into 80, 90, 100 wt% glycerol-water solution. The shockwave propagation is recorded by an ultra-high-speed camera taken at 100 Mfps together with a pulse laser stroboscope. The photographs are used to determine the shock front position as a function of time, which allows for calculating the shock pressure according to the stiffened-gas type Rankine-Hugoniot relation. It turns out that the initial plasma pressure is reduced by having higher glycerol concentration (i.e., higher viscosity); therefore, wave steepening effect is deemphasized, resulting in a smaller decay rate.
{"title":"Effects of Liquid Viscosity on Laser-Induced Shock Dynamics","authors":"Hiroki Kurahara, K. Ando","doi":"10.1115/ajkfluids2019-5151","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5151","url":null,"abstract":"\u0000 We experimentally study the effects of viscosity on laser-induced shockwave in glycerol-water solution. A shockwave is generated through rapid expansion of plasma, which is induced by focusing a 6 ns pulse laser (532 nm) of energy fixed at 1.66 ± 0.22 mJ into 80, 90, 100 wt% glycerol-water solution. The shockwave propagation is recorded by an ultra-high-speed camera taken at 100 Mfps together with a pulse laser stroboscope. The photographs are used to determine the shock front position as a function of time, which allows for calculating the shock pressure according to the stiffened-gas type Rankine-Hugoniot relation. It turns out that the initial plasma pressure is reduced by having higher glycerol concentration (i.e., higher viscosity); therefore, wave steepening effect is deemphasized, resulting in a smaller decay rate.","PeriodicalId":322380,"journal":{"name":"Volume 5: Multiphase Flow","volume":"97 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116205992","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}
Pub Date : 2019-11-20DOI: 10.1115/ajkfluids2019-4831
J. Furlan, K. Pagalthivarthi, H. Tian, P. Barsh, R. Visintainer
Empirical wear coefficients are used in concert with computational fluid dynamics (CFD) codes which model highly loaded slurry flows through centrifugal pumps in order to predict erosive wear in wet-end components. In practice, separate sets of wear coefficients are used to determine the contributions of sliding and impact wear to the total erosive wear at the wetted surface. In this study, experiments were performed in order to obtain the impact wear coefficients for sand in a water slurry impinging on high chrome white iron alloys that are commonly used in the construction of heavy duty centrifugal slurry pumps. Two separate sets of tests were completed using two different types of narrowly graded sand, with mass median particle diameters of approximately 600 μm and 300 μm respectively. The tests were performed in a closed loop containing a slurry pump, flow meter, inverted U loop for determination of the solids concentration, and 8 sample sections arranged serially. Each sample section was constructed from polyurethane, with rectangular flow cross sections of 1 inch (25.4 mm) width and 2 inch (50.8 mm) height and lengths of 1 foot (305 mm). One metal sample was placed into each sample holder so that it spanned across the 1 inch (25.4 mm) width and was exposed to the slurry flow, with its edges being supported by the flat polyurethane walls on either side. The samples were machined to have constant angles on the leading edge faces which varied from 10 to 60 degrees (from sample to sample), in order to obtain a range of impact angles (angle between the particle trajectory and the wetted surface) of the particles impinging on the sample leading edge faces. Tests were run at 12 % concentration by volume and at mean channel-sectional flow velocities of 10 m/s, with run times varying from 30 minutes to 180 minutes over the course of the test program. Slurry loop samples were taken at the beginning and end of each run in order to determine the particle size distribution and to monitor degradation of solids through sieve and micrograph analysis. The worn wedge face surfaces were scanned at intermittent times throughout the testing using an optical profilometer, and the local erosive wear was determined on the slanted face of, as well as at the tip of, the wedge-shaped samples. The progression of wear over the course of the test program was measured and analyzed in this manner. The local solids concentration, velocity, and impact angle was then predicted using in-house CFD codes formulated in the same manner as the pump wear models. The experimental wear profiles, together with the predicted local solids concentration, velocity, and impact angle, were then used to calculate the specific energy coefficient (or impact wear coefficient) at multiple impact angles. A formulation for the impact wear coefficient as a function of impact angle at a given particle size was then produced at each of the two different particle diameters. By comparing the data b
{"title":"Experimental Determination of Impact Wear Coefficients for Modeling of Erosion in Highly Loaded Slurry Flows","authors":"J. Furlan, K. Pagalthivarthi, H. Tian, P. Barsh, R. Visintainer","doi":"10.1115/ajkfluids2019-4831","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-4831","url":null,"abstract":"\u0000 Empirical wear coefficients are used in concert with computational fluid dynamics (CFD) codes which model highly loaded slurry flows through centrifugal pumps in order to predict erosive wear in wet-end components. In practice, separate sets of wear coefficients are used to determine the contributions of sliding and impact wear to the total erosive wear at the wetted surface. In this study, experiments were performed in order to obtain the impact wear coefficients for sand in a water slurry impinging on high chrome white iron alloys that are commonly used in the construction of heavy duty centrifugal slurry pumps. Two separate sets of tests were completed using two different types of narrowly graded sand, with mass median particle diameters of approximately 600 μm and 300 μm respectively.\u0000 The tests were performed in a closed loop containing a slurry pump, flow meter, inverted U loop for determination of the solids concentration, and 8 sample sections arranged serially. Each sample section was constructed from polyurethane, with rectangular flow cross sections of 1 inch (25.4 mm) width and 2 inch (50.8 mm) height and lengths of 1 foot (305 mm). One metal sample was placed into each sample holder so that it spanned across the 1 inch (25.4 mm) width and was exposed to the slurry flow, with its edges being supported by the flat polyurethane walls on either side. The samples were machined to have constant angles on the leading edge faces which varied from 10 to 60 degrees (from sample to sample), in order to obtain a range of impact angles (angle between the particle trajectory and the wetted surface) of the particles impinging on the sample leading edge faces. Tests were run at 12 % concentration by volume and at mean channel-sectional flow velocities of 10 m/s, with run times varying from 30 minutes to 180 minutes over the course of the test program. Slurry loop samples were taken at the beginning and end of each run in order to determine the particle size distribution and to monitor degradation of solids through sieve and micrograph analysis. The worn wedge face surfaces were scanned at intermittent times throughout the testing using an optical profilometer, and the local erosive wear was determined on the slanted face of, as well as at the tip of, the wedge-shaped samples. The progression of wear over the course of the test program was measured and analyzed in this manner.\u0000 The local solids concentration, velocity, and impact angle was then predicted using in-house CFD codes formulated in the same manner as the pump wear models. The experimental wear profiles, together with the predicted local solids concentration, velocity, and impact angle, were then used to calculate the specific energy coefficient (or impact wear coefficient) at multiple impact angles. A formulation for the impact wear coefficient as a function of impact angle at a given particle size was then produced at each of the two different particle diameters. By comparing the data b","PeriodicalId":322380,"journal":{"name":"Volume 5: Multiphase Flow","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125825573","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}
Pub Date : 2019-11-20DOI: 10.1115/ajkfluids2019-4685
Zhang Tianxing, Ayesha Almheiri, L. Khezzar, M. Alshehhi, Saqib Salam
This paper presents an experimental study conducted on turbulent single and two-phase swirling flow in a circular pipe with a bluff body. Laser Doppler Velocimetry (LDV) was used to measure liquid velocity radial profiles. The measurements were performed in a closed water-air loop system with a horizontal test section of length 610 mm and 41 mm internal diameter. The measurement campaign was performed at different axial locations to document the flow field without and with the presence of an air core respectively. The measurements were conducted with water flow rates which corresponded to Reynolds numbers based on pipe diameter and average liquid velocity of 14,500 and 19,450 for single phase and liquid-gas swirling flow, respectively. Analysis of the results reveals a more noticeable reverse flow along the whole pipe intensifying rather than being dampened as expected due to the swirl decay. High-speed photography shows that at a GLR = 0.3% the gas core does not touch the bluff body but breaks down just ahead of the disk surface.
{"title":"Experiments on Turbulent Air-Water Swirling Flow in a Pipe With a Circular Disk","authors":"Zhang Tianxing, Ayesha Almheiri, L. Khezzar, M. Alshehhi, Saqib Salam","doi":"10.1115/ajkfluids2019-4685","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-4685","url":null,"abstract":"\u0000 This paper presents an experimental study conducted on turbulent single and two-phase swirling flow in a circular pipe with a bluff body. Laser Doppler Velocimetry (LDV) was used to measure liquid velocity radial profiles. The measurements were performed in a closed water-air loop system with a horizontal test section of length 610 mm and 41 mm internal diameter. The measurement campaign was performed at different axial locations to document the flow field without and with the presence of an air core respectively. The measurements were conducted with water flow rates which corresponded to Reynolds numbers based on pipe diameter and average liquid velocity of 14,500 and 19,450 for single phase and liquid-gas swirling flow, respectively. Analysis of the results reveals a more noticeable reverse flow along the whole pipe intensifying rather than being dampened as expected due to the swirl decay. High-speed photography shows that at a GLR = 0.3% the gas core does not touch the bluff body but breaks down just ahead of the disk surface.","PeriodicalId":322380,"journal":{"name":"Volume 5: Multiphase Flow","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129892544","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}
Pub Date : 2019-11-20DOI: 10.1115/ajkfluids2019-5050
Mobina Mohammadikharkeshi, M. Parsi, Ramin Dabirian, R. Mohan, O. Shoham
Slug flow, which commonly occurs in the petroleum industry, is not always a desired flow pattern due to production operation problems it may cause in pipelines and processing facilities. To mitigate these problems, flow conditioning devices such as multiphase flow manifolds and slug catchers are used, where dissipation of slugs occurs in downward flow or in larger diameter pipe sections. Tee-junctions are important parts of these flow conditioning devices. In this work, Computational Fluid Dynamics (CFD) simulations are conducted using ANSYS/FLUENT 17.2 to investigate slug dissipation in an Enlarged Impacting Tee-Junction (EIT). An Eulerian–Eulerian MultiFluid VOF transient model in conjunction with the standard k-ε turbulent model is used to simulate slug dissipation in an EIT geometry. The EIT consists of a 0.05 m ID 10 m long inlet, which is connected to the center of a 0.074 m ID 5.5 m long section that forms the EIT branches. Moreover, experimental data are acquired on slug dissipation lengths in a horizontal EIT with a similar geometry as in the CFD simulations. The CFD results include the mean void fraction and cross-sectionally averaged void fraction time series in the EIT for different gas and liquid velocities. These results provide the inlet slug length and dissipation length in the EIT branches. The CFD results are evaluated against the experimental data demonstrating that the slug dissipation occurring in EIT branches can be predicted by simulation.
{"title":"CFD Simulation of Slug Dissipation in an Enlarged Impacting Tee","authors":"Mobina Mohammadikharkeshi, M. Parsi, Ramin Dabirian, R. Mohan, O. Shoham","doi":"10.1115/ajkfluids2019-5050","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5050","url":null,"abstract":"\u0000 Slug flow, which commonly occurs in the petroleum industry, is not always a desired flow pattern due to production operation problems it may cause in pipelines and processing facilities. To mitigate these problems, flow conditioning devices such as multiphase flow manifolds and slug catchers are used, where dissipation of slugs occurs in downward flow or in larger diameter pipe sections. Tee-junctions are important parts of these flow conditioning devices.\u0000 In this work, Computational Fluid Dynamics (CFD) simulations are conducted using ANSYS/FLUENT 17.2 to investigate slug dissipation in an Enlarged Impacting Tee-Junction (EIT). An Eulerian–Eulerian MultiFluid VOF transient model in conjunction with the standard k-ε turbulent model is used to simulate slug dissipation in an EIT geometry. The EIT consists of a 0.05 m ID 10 m long inlet, which is connected to the center of a 0.074 m ID 5.5 m long section that forms the EIT branches. Moreover, experimental data are acquired on slug dissipation lengths in a horizontal EIT with a similar geometry as in the CFD simulations.\u0000 The CFD results include the mean void fraction and cross-sectionally averaged void fraction time series in the EIT for different gas and liquid velocities. These results provide the inlet slug length and dissipation length in the EIT branches. The CFD results are evaluated against the experimental data demonstrating that the slug dissipation occurring in EIT branches can be predicted by simulation.","PeriodicalId":322380,"journal":{"name":"Volume 5: Multiphase Flow","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128917898","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}
Pub Date : 2019-11-20DOI: 10.1115/ajkfluids2019-5554
Anisha Mule, Ramin Dabirian, S. Kolla, R. Mohan, O. Shoham
A novel non-fibrous filter media is evaluated for in-line oil-water separation. Outside-in-crossflow configuration incorporating the filter media is utilized in order to test the filter. All experiments are conducted with a hydrophilic-olephobic filter for water-continuous flow with low oil concentrations. The collected experimental data include permeate flow rate and purity as well as pressure drop. Values of permeate flow rate and pressure drop are averaged over the duration of the experiments, which is about 5 minutes, constituting the “initial average” of the permeate flow rate and the corresponding pressure drop. Totally twelve experimental runs are conducted for mixture velocities of 0.038 m/s, 0.055 m/s and 0.066 m/s, and oil concentrations of 0.6%, 0.83%, 1.1%, 7.9% and 9.1%. Permeate samples are analyzed for oil content, demonstrating a high separation efficiency of 98 ± 2%. The permeate flux across the filter cartridge ranges between 0.0739 (L/h)/cm2 to 0.216 (L/h)/cm2 owing to the low pressure drop across to filter. Oil concentration in to permeate water samples shows consistently increasing trend with an increase in inlet oil content, while maintaining high separation efficiency for all runs. The pressure drop across the membrane under flowing conditions ranges from 0.35 psid to 0.6 psid for flow rates between 0.1 L/min and 0.29 L/min, respectively. Also the data confirm that the filter membrane breakthrough pressure is 0.35 psid.
{"title":"In-Line Testing of Novel Filter Media for Oil-Water Mixtures","authors":"Anisha Mule, Ramin Dabirian, S. Kolla, R. Mohan, O. Shoham","doi":"10.1115/ajkfluids2019-5554","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5554","url":null,"abstract":"\u0000 A novel non-fibrous filter media is evaluated for in-line oil-water separation. Outside-in-crossflow configuration incorporating the filter media is utilized in order to test the filter. All experiments are conducted with a hydrophilic-olephobic filter for water-continuous flow with low oil concentrations.\u0000 The collected experimental data include permeate flow rate and purity as well as pressure drop. Values of permeate flow rate and pressure drop are averaged over the duration of the experiments, which is about 5 minutes, constituting the “initial average” of the permeate flow rate and the corresponding pressure drop. Totally twelve experimental runs are conducted for mixture velocities of 0.038 m/s, 0.055 m/s and 0.066 m/s, and oil concentrations of 0.6%, 0.83%, 1.1%, 7.9% and 9.1%. Permeate samples are analyzed for oil content, demonstrating a high separation efficiency of 98 ± 2%.\u0000 The permeate flux across the filter cartridge ranges between 0.0739 (L/h)/cm2 to 0.216 (L/h)/cm2 owing to the low pressure drop across to filter. Oil concentration in to permeate water samples shows consistently increasing trend with an increase in inlet oil content, while maintaining high separation efficiency for all runs. The pressure drop across the membrane under flowing conditions ranges from 0.35 psid to 0.6 psid for flow rates between 0.1 L/min and 0.29 L/min, respectively. Also the data confirm that the filter membrane breakthrough pressure is 0.35 psid.","PeriodicalId":322380,"journal":{"name":"Volume 5: Multiphase Flow","volume":"116 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134330403","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}
Pub Date : 2019-11-20DOI: 10.1115/ajkfluids2019-4861
M. Tadjfar, A. Jaberi, R. Shokri
Perpendicular injection of liquid jets into gaseous crossflow is well-known as an effective way to obtain good mixing between liquid fuel and air crossflow. Mostly, injectors with circular holes were used as the standard method of fuel spraying. However, recently a great attention to injectors with non-circular holes has emerged that aims to improve the quality of fuel mixing and consequently combustion efficiency. In the present work, rectangular injectors with different aspect ratios varying from 1 to 4 were experimentally studied. Using a wind tunnel with maximum air velocity of 42 m/s, tests were performed for a wide range of flow conditions including liquid-to-air momentum ratios of 10, 20, 30 and 40. Backlight shadowgraphy and high speed photography were employed to capture the instantaneous physics of the liquid jets discharged into gaseous crossflow. The flow physics of the rectangular liquid jets were investigated by means of flow visualizations. Different regimes of flow breakup including capillary, arcade, bag and multimode were observed for rectangular jets. Moreover, a new technique was used to calculate the trajectory of the liquid jets. It was shown the nozzle’s shape has no significant effect on jet trajectory. Also, the momentum ratio was found to has a profound effect on jet trajectory.
{"title":"Flow Characteristics of Rectangular Liquid Jets Injected Into Low Subsonic Crossflow","authors":"M. Tadjfar, A. Jaberi, R. Shokri","doi":"10.1115/ajkfluids2019-4861","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-4861","url":null,"abstract":"\u0000 Perpendicular injection of liquid jets into gaseous crossflow is well-known as an effective way to obtain good mixing between liquid fuel and air crossflow. Mostly, injectors with circular holes were used as the standard method of fuel spraying. However, recently a great attention to injectors with non-circular holes has emerged that aims to improve the quality of fuel mixing and consequently combustion efficiency. In the present work, rectangular injectors with different aspect ratios varying from 1 to 4 were experimentally studied. Using a wind tunnel with maximum air velocity of 42 m/s, tests were performed for a wide range of flow conditions including liquid-to-air momentum ratios of 10, 20, 30 and 40. Backlight shadowgraphy and high speed photography were employed to capture the instantaneous physics of the liquid jets discharged into gaseous crossflow. The flow physics of the rectangular liquid jets were investigated by means of flow visualizations. Different regimes of flow breakup including capillary, arcade, bag and multimode were observed for rectangular jets. Moreover, a new technique was used to calculate the trajectory of the liquid jets. It was shown the nozzle’s shape has no significant effect on jet trajectory. Also, the momentum ratio was found to has a profound effect on jet trajectory.","PeriodicalId":322380,"journal":{"name":"Volume 5: Multiphase Flow","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121069297","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}
Pub Date : 2019-11-20DOI: 10.1115/ajkfluids2019-4959
I. V. Deschwanden, S. Braun, D. Brillert
Wet compression is a widely used approach to enhance the compressor performance of gas turbine units. For wet compression, a water-spray consisting of tiny droplets is injected into the air inlet duct of the compressor. A multi-phase flow of humid air and water droplets enters the compressor. The continued water evaporation inside the compressor stages causes further cooling during the compression process. Water injection between the compressor stages is called interstage injection. An advantage of interstage injection compared to wet compression is the optimized injection of water at specific positions inside the compressor. The amount of injected water can be adopted to the specific operating conditions of the different injection positions with the ideal of isothermal compression. Interstage injection can be realized by several techniques. This paper focuses on interstage injection of water from the trailing edge of stator blades. The water spray is generated in the complex wake flow of the airfoil. This leads to strong interaction between the water spray and the carrier gas flow. In this paper, especially the impact of water injection on the air flow and the spread of the spray is investigated. Phase Doppler Anemometry (PDA) measurements enable two dimensional velocity measurements linked with the droplet size. The comparison of PDA measurements and Computational Fluid Dynamic (CFD) calculations of the dry gas flow allows for the identification of flow instabilities due to interstage injection. Within this publication, a significant influence of the water injection from the trailing edge on the carrier flow is identified. Furthermore, the ability of the spray to spread widely into the flow demonstrates that water injection from the trailing edge is a promising technique for interstage injection.
{"title":"Effect of Interstage Injection on Compressor Flow Characteristic","authors":"I. V. Deschwanden, S. Braun, D. Brillert","doi":"10.1115/ajkfluids2019-4959","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-4959","url":null,"abstract":"\u0000 Wet compression is a widely used approach to enhance the compressor performance of gas turbine units. For wet compression, a water-spray consisting of tiny droplets is injected into the air inlet duct of the compressor. A multi-phase flow of humid air and water droplets enters the compressor. The continued water evaporation inside the compressor stages causes further cooling during the compression process.\u0000 Water injection between the compressor stages is called interstage injection. An advantage of interstage injection compared to wet compression is the optimized injection of water at specific positions inside the compressor. The amount of injected water can be adopted to the specific operating conditions of the different injection positions with the ideal of isothermal compression.\u0000 Interstage injection can be realized by several techniques. This paper focuses on interstage injection of water from the trailing edge of stator blades. The water spray is generated in the complex wake flow of the airfoil. This leads to strong interaction between the water spray and the carrier gas flow.\u0000 In this paper, especially the impact of water injection on the air flow and the spread of the spray is investigated. Phase Doppler Anemometry (PDA) measurements enable two dimensional velocity measurements linked with the droplet size. The comparison of PDA measurements and Computational Fluid Dynamic (CFD) calculations of the dry gas flow allows for the identification of flow instabilities due to interstage injection. Within this publication, a significant influence of the water injection from the trailing edge on the carrier flow is identified. Furthermore, the ability of the spray to spread widely into the flow demonstrates that water injection from the trailing edge is a promising technique for interstage injection.","PeriodicalId":322380,"journal":{"name":"Volume 5: Multiphase Flow","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114673689","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}
Pub Date : 2019-11-20DOI: 10.1115/ajkfluids2019-5457
I. Kumagai, Kakeru Taguchi, C. Kawakita, T. Hamada, Y. Murai
Air entrainment and bubble generation by a hydrofoil bubble generator for ship drag reduction have been investigated using a small high-speed channel tunnel with the gap of 20 mm in National Maritime Research Institute (NMRI). A hydrofoil (NACA4412, chord length = 40 mm) was installed in the channel and an air induction pipe was placed above the hydrofoil. The flow rate of the entrained air was quantitatively measured by thermal air flow sensors at the inlet of the air induction pipe. The gas-liquid flow around the hydrofoil was visualized by a backlight method and recorded by a high-speed video camera. As the flow velocity in the channel increased, the negative pressure generated above the suction side of the hydrofoil lowered the hydrostatic pressure in the channel, then the atmospheric air was entrained into the channel flow. The entrained air was broken into small air bubbles by the turbulent flow in the channel. The threshold of air entrainment, the air flow rate, and gas-liquid flow pattern depends on Reynolds number, angle of attack (AOA), and hydrofoil type. We identified at least three modes of air entrainment behavior: intermittent air entrainment, stable air entrainment, and air entrainment with a ventilated cavity. At high flow speed in our experimental condition (9 m/s), a large volume of air bubbles was generated by this hydrofoil system (e.g. air flow rate was 50 l/min for NACA4412 at AOA 16 degrees), which has a high potential to reduce ship drag.
{"title":"Air Entrainment and Bubble Generation by a Hydrofoil in a Turbulent Channel Flow","authors":"I. Kumagai, Kakeru Taguchi, C. Kawakita, T. Hamada, Y. Murai","doi":"10.1115/ajkfluids2019-5457","DOIUrl":"https://doi.org/10.1115/ajkfluids2019-5457","url":null,"abstract":"\u0000 Air entrainment and bubble generation by a hydrofoil bubble generator for ship drag reduction have been investigated using a small high-speed channel tunnel with the gap of 20 mm in National Maritime Research Institute (NMRI). A hydrofoil (NACA4412, chord length = 40 mm) was installed in the channel and an air induction pipe was placed above the hydrofoil. The flow rate of the entrained air was quantitatively measured by thermal air flow sensors at the inlet of the air induction pipe. The gas-liquid flow around the hydrofoil was visualized by a backlight method and recorded by a high-speed video camera. As the flow velocity in the channel increased, the negative pressure generated above the suction side of the hydrofoil lowered the hydrostatic pressure in the channel, then the atmospheric air was entrained into the channel flow. The entrained air was broken into small air bubbles by the turbulent flow in the channel. The threshold of air entrainment, the air flow rate, and gas-liquid flow pattern depends on Reynolds number, angle of attack (AOA), and hydrofoil type. We identified at least three modes of air entrainment behavior: intermittent air entrainment, stable air entrainment, and air entrainment with a ventilated cavity. At high flow speed in our experimental condition (9 m/s), a large volume of air bubbles was generated by this hydrofoil system (e.g. air flow rate was 50 l/min for NACA4412 at AOA 16 degrees), which has a high potential to reduce ship drag.","PeriodicalId":322380,"journal":{"name":"Volume 5: Multiphase Flow","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115002317","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}
Pub Date : 2019-11-20DOI: 10.1115/ajkfluids2019-5612
K. Mizutori, K. Fukudome, M. Yamamoto, Masaya Suzuki
We performed numerical simulation to understand deposition phenomena on high-pressure turbine vane. Several deposition models were compared and the OSU model showed good adaptation to any flow field and material, so it was implemented on UPACS. After the implementation, the simulations of deposition phenomenon in several cases of the flow field were conducted. From the results, particles adhere on the leading edge and the trailing edge side of the pressure surface. Also, the calculation of the total pressure loss coefficient was conducted after computing the flow field after deposition. The total pressure loss coefficient increased after deposition and it was revealed that the deposition deteriorates aerodynamic performance.
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Pub Date : 2019-11-20DOI: 10.1115/ajkfluids2019-5458
B. Angle, M. Rau, M. Byron
In natural sedimentation, many particles of interest are both large and nonspherical. Some common particle types (e.g. naturally occurring aggregates) do not have a uniform mass distribution. As a result, the centers of mass and buoyancy are not co-located, leading to more complex settling dynamics. Here we investigated the orientation and terminal velocity of freely falling cylinders, in which the mass distribution was either constant (uniform-density, UD) or bipartite, undergoing a step function halfway along the length (compound-density, CD). Cylinders had relatively low aspect ratios (1 < AR < 4), and fell at intermediate Reynolds numbers (of order 100). The cylinders, initially horizontal, were released at the top of a tall hexagonal still-water tank, and imaged by a high-speed camera. Two low-speed cameras simultaneously captured 1) full cylinder trajectory and 2) landing position. We recorded the terminal velocity, fall orientation, and landing site of each cylinder. Results showed significant differences in the settling characteristics of uniform- vs. compound-density cylinders. UD cylinders of AR = 1 fell broadside initially, whereas AR = 1 CD cylinders fell vertically. However, both cases showed oscillation in cylinder orientation upon descent. UD cylinders with AR = 2 and AR = 4 consistently fell broadside, with minimal cylinder axis oscillation. CD cylinders with AR = 2 fell with two different modes. In mode 1, cylinders rotated 90° from their initial orientation before beginning to oscillate about the vertical axis. In mode 2, cylinder orientation remained constant at a slight angle from the horizontal. This mode was also observed in the CD AR = 4 cylinders, which fell at a constant (tilted) orientation angle and moved horizontally as they fell. The landing sites for all CD cylinders were biased toward the side of the target where the denser end of the cylinder was initially oriented, whereas UD cylinders landed in a uniform distribution around the tank center. In general, cylinders with the smallest vertical projected area fell with the greatest terminal velocity; however, the mechanisms controlling orientation remain unclear. Our results have important implications for predicting the settling behavior of naturally-occurring particles, and lay the groundwork for further study of particles settling in complex flows such as turbulence. Given our results in still water, the interplay between the buoyant torques created by the offset between the center of mass and center of volume are likely to strongly impact particle motion in turbulence.
在自然沉降中，许多感兴趣的颗粒既大又非球形。一些常见的颗粒类型(如自然产生的聚集体)没有均匀的质量分布。因此，质量中心和浮力中心不在同一位置，导致更复杂的沉降动力学。在这里，我们研究了自由下落圆柱体的方向和终端速度，其中质量分布要么是恒定的(均匀密度，UD)，要么是二部的，沿着长度的一半经历阶跃函数(化合物密度，CD)。圆柱体的长径比相对较低(1 < AR < 4)，并且在中间雷诺数(100数量级)下降。这些圆柱体最初是水平的，在一个高大的六角形静水箱的顶部释放出来，由高速摄像机拍摄。两台低速摄像机同时捕捉到1)整个气缸轨迹和2)着陆位置。我们记录了每个圆柱体的最终速度、下落方向和着陆点。结果表明均匀密度圆柱体与复合密度圆柱体的沉降特性有显著差异。AR = 1的UD圆柱体最初是沿侧面落下的，而AR = 1的CD圆柱体是垂直落下的。然而，这两种情况下均表现出下降时柱体方向的振荡。当AR = 2和AR = 4时，UD圆柱体的侧壁一致，圆柱体轴向振荡最小。AR = 2的CD圆柱体有两种不同的落模。在模式1中，圆柱体在开始绕垂直轴振荡之前从其初始方向旋转90°。在模态2中，圆柱体方向保持恒定，与水平面有一个小角度。在CD AR = 4圆柱体中也观察到这种模式，它们以恒定的(倾斜的)取向角下落，并在下落时水平移动。所有CD圆柱体的着陆点都偏向于目标的一侧，即圆柱体密度较大的一端最初朝向的位置，而UD圆柱体则均匀分布在罐中心周围。一般来说，垂直投影面积最小的圆柱体下落时的终端速度最大;然而，控制取向的机制尚不清楚。我们的研究结果对预测自然粒子的沉降行为具有重要意义，并为进一步研究湍流等复杂流动中的粒子沉降奠定了基础。考虑到我们在静水中的结果，质心和体积中心之间的偏移产生的浮力扭矩之间的相互作用可能会强烈影响湍流中的粒子运动。
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