Dynamic stall is dominant to aerodynamic performance of vertical axis wind turbines where angles of attack (AoAs) of blades vary periodically during operation. Therefore, dynamic stall models are necessarily employed in the simulation of wind turbines. Among them the Leishmen-Beddoes (LB) dynamic stall model are widely accepted nowadays. In the LB model, aerodynamic forces of blades are determined by AoAs and their rates of change. However, in consideration of the inevitable existence of numerical errors of AoAs, calculations of the rates of change may cause unexpected numerical problems. This paper focused on presence of fluctuations of blade forces due to minor numerical errors of AoAs in the LB model. Then three modifications, namely the implementation of filters of AoAs, alternative calculation of change of variables and scaling of time constants, were employed and their effect on numerical stability of the LB model was evaluated. It is found that the implementation of filters of AoAs can eliminate fluctuations of outcome forces but the phase delay is the side effect. In addition, alternative calculation of change of variables and scaling of time constants can reduce the maximum nominal fluctuations of results from 16.4% to 5.8% and 5.1%, respectively.
{"title":"Several Modifications to Improve Numerical Stability of Leishmen-Beddoes Dynamic Stall Model","authors":"Jia Guo, Haoran Meng, P. Zeng, Li-ping Lei","doi":"10.1115/fedsm2020-20387","DOIUrl":"https://doi.org/10.1115/fedsm2020-20387","url":null,"abstract":"\u0000 Dynamic stall is dominant to aerodynamic performance of vertical axis wind turbines where angles of attack (AoAs) of blades vary periodically during operation. Therefore, dynamic stall models are necessarily employed in the simulation of wind turbines. Among them the Leishmen-Beddoes (LB) dynamic stall model are widely accepted nowadays. In the LB model, aerodynamic forces of blades are determined by AoAs and their rates of change. However, in consideration of the inevitable existence of numerical errors of AoAs, calculations of the rates of change may cause unexpected numerical problems. This paper focused on presence of fluctuations of blade forces due to minor numerical errors of AoAs in the LB model. Then three modifications, namely the implementation of filters of AoAs, alternative calculation of change of variables and scaling of time constants, were employed and their effect on numerical stability of the LB model was evaluated. It is found that the implementation of filters of AoAs can eliminate fluctuations of outcome forces but the phase delay is the side effect. In addition, alternative calculation of change of variables and scaling of time constants can reduce the maximum nominal fluctuations of results from 16.4% to 5.8% and 5.1%, respectively.","PeriodicalId":103887,"journal":{"name":"Volume 1: Fluid Applications and Systems; Fluid Measurement and Instrumentation","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130789536","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}
An experimental investigation for evaporation frictional pressure drop in horizontal enhanced tubes with an outer diameter of 12.7 mm was studied using R410A as the working fluid. The experiment was conducted: the mass flux in the range of 100 kg/(m2s) to 200 kg/(m2s), over a vapor quality range of 0.2 to 0.8, an average saturation temperature at 279 K. The inner tubes were the tested tubes, which included a smooth tube, a three-dimensional enhanced tube (a tube enhanced by protrusions and petal arrays background patterns), respectively. The results show that the frictional pressure drop increases with the mass flux increasing. Moreover, the frictional pressure drop of the enhanced tube is 1.6∼2.4 times than that of the smooth tube. This is mainly due to the increase of the flow resistance inside the enhanced tube, which is caused by the increased interfacial turbulence, flow separation and secondary flow. It is also observed that the pressure drop increases with vapor quality increasing. In addition, some existing correlations are used to compare with our experimental data and verify their accuracy. A new modified correlation is proposed to predict the frictional pressure drop of EHT-1 tube.
{"title":"Experimental Study of Evaporation Frictional Pressure Drop in Horizontal Enhanced Tube","authors":"Zong-bao Gu, Yu Guo, Xiang Ma, Yan He, Wei Li","doi":"10.1115/fedsm2020-20134","DOIUrl":"https://doi.org/10.1115/fedsm2020-20134","url":null,"abstract":"An experimental investigation for evaporation frictional pressure drop in horizontal enhanced tubes with an outer diameter of 12.7 mm was studied using R410A as the working fluid. The experiment was conducted: the mass flux in the range of 100 kg/(m2s) to 200 kg/(m2s), over a vapor quality range of 0.2 to 0.8, an average saturation temperature at 279 K. The inner tubes were the tested tubes, which included a smooth tube, a three-dimensional enhanced tube (a tube enhanced by protrusions and petal arrays background patterns), respectively. The results show that the frictional pressure drop increases with the mass flux increasing. Moreover, the frictional pressure drop of the enhanced tube is 1.6∼2.4 times than that of the smooth tube. This is mainly due to the increase of the flow resistance inside the enhanced tube, which is caused by the increased interfacial turbulence, flow separation and secondary flow. It is also observed that the pressure drop increases with vapor quality increasing. In addition, some existing correlations are used to compare with our experimental data and verify their accuracy. A new modified correlation is proposed to predict the frictional pressure drop of EHT-1 tube.","PeriodicalId":103887,"journal":{"name":"Volume 1: Fluid Applications and Systems; Fluid Measurement and Instrumentation","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122103370","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}
Seyedmohammad Mousavisani, S. Kelly, Sajad Kafashi, S. Smith
The encoded Particle Tracking Velocimetry (ePTV) is introduce in this paper as a specific approach of Particle Tracking Velocimetry (PTV). This method is applied to track particles obtained from flow images that contain significant background noise and relatively low particle density. Encoding is achieved by illuminating the flow with a series of light pulses within individual image exposures. Dependent upon the velocity, each particle will be illuminated multiple times in each image frame with spacing determined by both the pulse train timing and the particle velocity. A search algorithm is used that identifies each particle and seeks the encoded pattern with other particles in the image, repeating this until all encoded particles are found. Based on probability analysis and finite image size an analytic model is developed to determine the ratio of true particles, false particles and those that are ‘lost’ by exiting the image frame. This ePTV technique has been experimentally implemented to track spherical particles suspended in stationary vortices. By using a suspension of micro-particles, subsequent imaging with encoded pulse trains provided snap-shots of the complex flow patterns. Typically, even after filtering, the images show around 100 to 200 particles from which encoded trajectories have been extracted and typically account for about 30% of the objects identified in the image.
{"title":"Particle Tracking Velocimetry in Noisy Environment","authors":"Seyedmohammad Mousavisani, S. Kelly, Sajad Kafashi, S. Smith","doi":"10.1115/fedsm2020-20401","DOIUrl":"https://doi.org/10.1115/fedsm2020-20401","url":null,"abstract":"\u0000 The encoded Particle Tracking Velocimetry (ePTV) is introduce in this paper as a specific approach of Particle Tracking Velocimetry (PTV). This method is applied to track particles obtained from flow images that contain significant background noise and relatively low particle density. Encoding is achieved by illuminating the flow with a series of light pulses within individual image exposures. Dependent upon the velocity, each particle will be illuminated multiple times in each image frame with spacing determined by both the pulse train timing and the particle velocity. A search algorithm is used that identifies each particle and seeks the encoded pattern with other particles in the image, repeating this until all encoded particles are found.\u0000 Based on probability analysis and finite image size an analytic model is developed to determine the ratio of true particles, false particles and those that are ‘lost’ by exiting the image frame.\u0000 This ePTV technique has been experimentally implemented to track spherical particles suspended in stationary vortices.\u0000 By using a suspension of micro-particles, subsequent imaging with encoded pulse trains provided snap-shots of the complex flow patterns. Typically, even after filtering, the images show around 100 to 200 particles from which encoded trajectories have been extracted and typically account for about 30% of the objects identified in the image.","PeriodicalId":103887,"journal":{"name":"Volume 1: Fluid Applications and Systems; Fluid Measurement and Instrumentation","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115599481","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}
D. M. Rocha, F. Kanizawa, Kosuke Hayashi, S. Hosokawa, A. Tomiyama, G. Ribatski
This paper presents an analysis of the performance of the Spatial Filter Velocimetry (SFV) technique applied to external flows across tube bundles to evaluate the benefits of using low particle concentration in a complex geometry. The experimental vector velocity fields were obtained in a tube bundle test section made of acrylic with 20 rows of 4 tubes of 20mm O.D. mounted in a normal triangular configuration and transversal pitch per diameter ratio of 1.25. The SFV results reliability was evaluated by comparing the volumetric flow rates estimated by the experimental vector velocity fields with the volumetric flow rates measured by the flowmeter, showing good agreement. Additionally, the experimental results are used to check the validity of numerical results obtained through CFD simulation. The experiments were conducted for Reynolds numbers of 909, 1842 and 3902. The velocity profiles obtained through the SFV technique agree with the CFD simulations results, which indicate consistent results for both analyzes. Therefore, the numerical and experimental results indicate that the SFV technique provides accurate velocity data and is suitable to be applied to complex geometries, especially in regions away of the test section wall due to the good visibility provided by low particle concentration.
{"title":"A Comparison of the Flow Structure in a Normal Triangular Tube Array Obtained Based on the SFV Technique and on a CFD Analysis","authors":"D. M. Rocha, F. Kanizawa, Kosuke Hayashi, S. Hosokawa, A. Tomiyama, G. Ribatski","doi":"10.1115/fedsm2020-20251","DOIUrl":"https://doi.org/10.1115/fedsm2020-20251","url":null,"abstract":"\u0000 This paper presents an analysis of the performance of the Spatial Filter Velocimetry (SFV) technique applied to external flows across tube bundles to evaluate the benefits of using low particle concentration in a complex geometry. The experimental vector velocity fields were obtained in a tube bundle test section made of acrylic with 20 rows of 4 tubes of 20mm O.D. mounted in a normal triangular configuration and transversal pitch per diameter ratio of 1.25. The SFV results reliability was evaluated by comparing the volumetric flow rates estimated by the experimental vector velocity fields with the volumetric flow rates measured by the flowmeter, showing good agreement. Additionally, the experimental results are used to check the validity of numerical results obtained through CFD simulation. The experiments were conducted for Reynolds numbers of 909, 1842 and 3902. The velocity profiles obtained through the SFV technique agree with the CFD simulations results, which indicate consistent results for both analyzes. Therefore, the numerical and experimental results indicate that the SFV technique provides accurate velocity data and is suitable to be applied to complex geometries, especially in regions away of the test section wall due to the good visibility provided by low particle concentration.","PeriodicalId":103887,"journal":{"name":"Volume 1: Fluid Applications and Systems; Fluid Measurement and Instrumentation","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134471652","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}
Centrifugal compressor is one of the key components in the Super-critical carbon dioxide (SCO2) Brayton cycle process, its performance prediction under variable operating conditions are concerned a lot with consideration of the unique of SCO2 properties. At the same time, the general techniques, including numerical simulation, test, and theoretical analysis with the loss models, are applied to evaluate the compressor performance. In addition with numerical analysis on the performance of the compressor, the flow loss models from air compressor were studied and extended the application to the SCO2 compressors, including incidence loss, blade loading loss, passage flow loss, tip clearance loss, mixing loss, disk friction loss, vaneless diffuser loss. All of these models were investigated to get the performance of a SCO2 compressor. The CO2 quality was got from the multipurpose NIST REFPROP 9.0 (NiST) which is based on Span and Wagner equation of state. The quality was added in the numerical simulation process. Besides, the passage flow loss factor has been modified to get more accurate theoretical performance prediction method for SCO2 compressor. The predicted performance map was compared to the numerical results, and the comparison results proved that, the combination of the loss models provided the similar results as those from the numerical simulation. For the SCO2 centrifugal compressor, the passage flow loss covers the most part among all the compressor flow losses. The value of the passage flow loss factor applied in the theoretical performance prediction method ranges between 0.008∼0.025, which is higher than that for air. Finally, the performance evaluation by improved loss models at different compression starting points were compared with that by the numerical results, it was found that, closer to the critical point would make the passage flow loss increase a lot, which may even exceed its rational range and the produced loss would be beyond expectation. This might be the reason for the low efficiency of SCO2 compressor in the practical working conditions.
{"title":"Performance Evaluation for SCO2 Compressor With Loss Models Consideration","authors":"Yiting Huang, Tong Wang","doi":"10.1115/fedsm2020-20230","DOIUrl":"https://doi.org/10.1115/fedsm2020-20230","url":null,"abstract":"\u0000 Centrifugal compressor is one of the key components in the Super-critical carbon dioxide (SCO2) Brayton cycle process, its performance prediction under variable operating conditions are concerned a lot with consideration of the unique of SCO2 properties. At the same time, the general techniques, including numerical simulation, test, and theoretical analysis with the loss models, are applied to evaluate the compressor performance. In addition with numerical analysis on the performance of the compressor, the flow loss models from air compressor were studied and extended the application to the SCO2 compressors, including incidence loss, blade loading loss, passage flow loss, tip clearance loss, mixing loss, disk friction loss, vaneless diffuser loss. All of these models were investigated to get the performance of a SCO2 compressor. The CO2 quality was got from the multipurpose NIST REFPROP 9.0 (NiST) which is based on Span and Wagner equation of state. The quality was added in the numerical simulation process. Besides, the passage flow loss factor has been modified to get more accurate theoretical performance prediction method for SCO2 compressor. The predicted performance map was compared to the numerical results, and the comparison results proved that, the combination of the loss models provided the similar results as those from the numerical simulation. For the SCO2 centrifugal compressor, the passage flow loss covers the most part among all the compressor flow losses. The value of the passage flow loss factor applied in the theoretical performance prediction method ranges between 0.008∼0.025, which is higher than that for air. Finally, the performance evaluation by improved loss models at different compression starting points were compared with that by the numerical results, it was found that, closer to the critical point would make the passage flow loss increase a lot, which may even exceed its rational range and the produced loss would be beyond expectation. This might be the reason for the low efficiency of SCO2 compressor in the practical working conditions.","PeriodicalId":103887,"journal":{"name":"Volume 1: Fluid Applications and Systems; Fluid Measurement and Instrumentation","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122838768","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}
Amirkhosro Kazemi, Eduardo E. Castillo, O. Curet, R. Hortensius, Pothos Stamatios
Mangrove roots produce complex flow structure interactions with their environment, which affect the nutrient, habitat and aquatic animals. Analysis of the flow structure behind the roots extends to a broad range of mangrove-inspired applications that provides understanding into complex flows encountered in unidirectional riverine flows. In this work, we modeled the mangrove roots with a cluster of rigid circular cylinders to investigate the vortex structure downstream of the models. The vortex organization of the patch of cylinder wakes was studied experimentally by time-resolved volumetric three-componential volumetric velocimetry (V3V) at Reynolds numbers 1014 and 3549. The results show that the vortex structure in the 3-D flow field reveals a regular shedding at Re = 1014, forming von Kármán vortices dominating the 3D motion. The flow structure behind rigid patches is coherent and the streamwise velocity remains unchanged. The regime for a flexible patch at Re = 3549 produces an intricate pattern where the multiple counter-rotating vortexes distorted substantially and forming a chain of rhombus-like vortex cells in the near wake. The information for the 3D flow feature provides useful information to a robust structure for Seawall erosion.
{"title":"Volumetric Three-Componential Velocity Measurements (V3V) of Flow Structure Behind Mangrove-Root Type Models","authors":"Amirkhosro Kazemi, Eduardo E. Castillo, O. Curet, R. Hortensius, Pothos Stamatios","doi":"10.1115/fedsm2020-20461","DOIUrl":"https://doi.org/10.1115/fedsm2020-20461","url":null,"abstract":"\u0000 Mangrove roots produce complex flow structure interactions with their environment, which affect the nutrient, habitat and aquatic animals. Analysis of the flow structure behind the roots extends to a broad range of mangrove-inspired applications that provides understanding into complex flows encountered in unidirectional riverine flows. In this work, we modeled the mangrove roots with a cluster of rigid circular cylinders to investigate the vortex structure downstream of the models. The vortex organization of the patch of cylinder wakes was studied experimentally by time-resolved volumetric three-componential volumetric velocimetry (V3V) at Reynolds numbers 1014 and 3549. The results show that the vortex structure in the 3-D flow field reveals a regular shedding at Re = 1014, forming von Kármán vortices dominating the 3D motion. The flow structure behind rigid patches is coherent and the streamwise velocity remains unchanged. The regime for a flexible patch at Re = 3549 produces an intricate pattern where the multiple counter-rotating vortexes distorted substantially and forming a chain of rhombus-like vortex cells in the near wake. The information for the 3D flow feature provides useful information to a robust structure for Seawall erosion.","PeriodicalId":103887,"journal":{"name":"Volume 1: Fluid Applications and Systems; Fluid Measurement and Instrumentation","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114228078","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}
N. Hadi, B. Jawad, Munther Y. Hermez, H. Metwally, Liping Liu
Designing a turbomachine comes with many challenges due to many parameters affecting its performance. This study presents a design to reduce losses in turbulence flow and surface friction by using a disk located between the rotating centrifugal impeller and the pump casing, which in turn enhances the centrifugal pump performance, upon rotating freely during normal operation. Under a constant operating speed of 3000 RPM, the new design is shown to improve the centrifugal pump performance. The turbulent flow between the rotating impeller and pump stationary walls increases the frictional losses. The highest friction occurs in the flow between two surfaces, one being close to zero velocity and the other one moving at high speed. Flow recirculation in the enclosure is a major problem that leads to a decrease in turbomachine’s performance. Two-dimensional Computational Fluid Dynamics (CFD) analysis is used to numerically simulate the rotating flow field inside the centrifugal pump chamber and to provide critical hydraulic design information. In this study, ANSYS-FLUENT R19.2 is used to analyze the input torque under different angular velocities by applying a disk with various thicknesses at four different locations to get the best results. The flow field in the chamber is investigated using 2-D Naiver-Stokes Equations with a Realizable k-ϵ turbulence model. Standard water was used as the working fluid. The numerical analysis gives an idea of how the freely rotating disks behave, and the results will be compared to find the most efficient case of centrifugal pump operation with an adjacent disk. The best-case new design will identify the highest reduction of input power by 24.4%. This study will introduce to the future work of a three-dimensional model.
{"title":"CFD Simulation and Design Improvement of Internal Rotating Flow of Turbomachine","authors":"N. Hadi, B. Jawad, Munther Y. Hermez, H. Metwally, Liping Liu","doi":"10.1115/fedsm2020-20081","DOIUrl":"https://doi.org/10.1115/fedsm2020-20081","url":null,"abstract":"\u0000 Designing a turbomachine comes with many challenges due to many parameters affecting its performance. This study presents a design to reduce losses in turbulence flow and surface friction by using a disk located between the rotating centrifugal impeller and the pump casing, which in turn enhances the centrifugal pump performance, upon rotating freely during normal operation. Under a constant operating speed of 3000 RPM, the new design is shown to improve the centrifugal pump performance.\u0000 The turbulent flow between the rotating impeller and pump stationary walls increases the frictional losses. The highest friction occurs in the flow between two surfaces, one being close to zero velocity and the other one moving at high speed. Flow recirculation in the enclosure is a major problem that leads to a decrease in turbomachine’s performance. Two-dimensional Computational Fluid Dynamics (CFD) analysis is used to numerically simulate the rotating flow field inside the centrifugal pump chamber and to provide critical hydraulic design information. In this study, ANSYS-FLUENT R19.2 is used to analyze the input torque under different angular velocities by applying a disk with various thicknesses at four different locations to get the best results. The flow field in the chamber is investigated using 2-D Naiver-Stokes Equations with a Realizable k-ϵ turbulence model. Standard water was used as the working fluid. The numerical analysis gives an idea of how the freely rotating disks behave, and the results will be compared to find the most efficient case of centrifugal pump operation with an adjacent disk. The best-case new design will identify the highest reduction of input power by 24.4%. This study will introduce to the future work of a three-dimensional model.","PeriodicalId":103887,"journal":{"name":"Volume 1: Fluid Applications and Systems; Fluid Measurement and Instrumentation","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132201976","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}
Masahito Watanabe, Y. Kitamura, N. Hatta, Hiroaki Yoshimura
It is known that some fluid particles may be transported chaotically in Lagrangian description although the velocity field seems to be stable in Eulerian description. A typical example can be found in the system of two-dimensional Rayleigh-Benard convection with perturbed velocity fields, which has been investigated as a low dimensional mechanical model of fluid phenomena associated with natural convection in order to clarify the mechanism of fluid transport (see, for instance, [2]). In this study, we make an experimental study on the global structures of chaotic mixing appeared in the two-dimensional perturbed Rayleigh-Benard convection by analyzing Lagrangian coherent structures (LCSs), which correspond to the invariant manifolds of time-dependent mechanical systems. We develop an apparatus to measure the velocity field by Particle Image Velocimetry (PIV) and then show the LCSs which can be numerically detected from the experimental data by computing Finite-time Lyapunov exponent (FTLE) fields. Finally, we show the global structures of chaotic mixing appeared in the perturbed Rayleigh-Benard convection as well as the steady convection by experiments. In particular, we clarify how the LCSs are entangled with each other around the cell boundaries to carry out chaotic Lagrangian transports.
{"title":"Experimental Analysis of Lagrangian Coherent Structures and Chaotic Mixing in Rayleigh-Benard Convection","authors":"Masahito Watanabe, Y. Kitamura, N. Hatta, Hiroaki Yoshimura","doi":"10.1115/fedsm2020-20116","DOIUrl":"https://doi.org/10.1115/fedsm2020-20116","url":null,"abstract":"\u0000 It is known that some fluid particles may be transported chaotically in Lagrangian description although the velocity field seems to be stable in Eulerian description. A typical example can be found in the system of two-dimensional Rayleigh-Benard convection with perturbed velocity fields, which has been investigated as a low dimensional mechanical model of fluid phenomena associated with natural convection in order to clarify the mechanism of fluid transport (see, for instance, [2]). In this study, we make an experimental study on the global structures of chaotic mixing appeared in the two-dimensional perturbed Rayleigh-Benard convection by analyzing Lagrangian coherent structures (LCSs), which correspond to the invariant manifolds of time-dependent mechanical systems. We develop an apparatus to measure the velocity field by Particle Image Velocimetry (PIV) and then show the LCSs which can be numerically detected from the experimental data by computing Finite-time Lyapunov exponent (FTLE) fields. Finally, we show the global structures of chaotic mixing appeared in the perturbed Rayleigh-Benard convection as well as the steady convection by experiments. In particular, we clarify how the LCSs are entangled with each other around the cell boundaries to carry out chaotic Lagrangian transports.","PeriodicalId":103887,"journal":{"name":"Volume 1: Fluid Applications and Systems; Fluid Measurement and Instrumentation","volume":"120 17","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120842331","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}
Digital holographic microscopy (DHM) enables 3D volumetric measurements of small objects with high magnification. DHM has been applied to measure a variety of experimental studies, including turbulent boundary layer, spray droplets, individual cells, development of zebrafish embryo, etc. In this study, a DHM system is applied to measure the morphology and locomotion of two groups of Caenorhabditis Elegans (C. Elegans) with different development conditions (ATGL-1 group and n2 group) in an 8-day time period from their hatching to the adult stage, whose body lengths range from hundreds of micrometers to one millimeter. The length and volume are determined to describe the morphology of the C. Elegans at different development stages. The locomotion of the C. Elegans is divided into linear motion and curl motion. The kinetic energy derived from the two types of motion describes the extent of how active the C. Elegans is. The statistics of morphology and locomotion of the two groups of C. Elegans are compared at different development stages to illustrate the influence of the applied development conditions.
{"title":"Measurements of Morphology and Locomotion of Caenorhabditis Elegans With Digital Holographic Microscopy","authors":"Yijie Wang, Jun Chen, Yuan Zhang, Kee-Hong Kim","doi":"10.1115/fedsm2020-20177","DOIUrl":"https://doi.org/10.1115/fedsm2020-20177","url":null,"abstract":"\u0000 Digital holographic microscopy (DHM) enables 3D volumetric measurements of small objects with high magnification. DHM has been applied to measure a variety of experimental studies, including turbulent boundary layer, spray droplets, individual cells, development of zebrafish embryo, etc. In this study, a DHM system is applied to measure the morphology and locomotion of two groups of Caenorhabditis Elegans (C. Elegans) with different development conditions (ATGL-1 group and n2 group) in an 8-day time period from their hatching to the adult stage, whose body lengths range from hundreds of micrometers to one millimeter. The length and volume are determined to describe the morphology of the C. Elegans at different development stages. The locomotion of the C. Elegans is divided into linear motion and curl motion. The kinetic energy derived from the two types of motion describes the extent of how active the C. Elegans is. The statistics of morphology and locomotion of the two groups of C. Elegans are compared at different development stages to illustrate the influence of the applied development conditions.","PeriodicalId":103887,"journal":{"name":"Volume 1: Fluid Applications and Systems; Fluid Measurement and Instrumentation","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125849769","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}
Jia-yi Wu, Yang Yue, Jia-Ming Yang, Zhi-jiang Jin, J. Qian
The sleeve regulating valve is a typical flow regulating component, which is indispensable in various industrial applications. This work investigates the effects of the body structure on the overall performance and the flow characteristic of a sleeve regulating valve. The anterior cavity h, the diameter of the center cavity Dc, and the eccentricity of the center cavity e are studied in a parametric way. When the relative increment of h, Dc, and e all take the value of 0.15, the rated flow coefficient Kve of the optimized valve is promoted by 33.99% relative to the Kve of the original model. The optimized model presents less wear between the valve core and the sleeve relative to the original model. It results from the fact that the non-centrosymmetric pressure distribution is reduced on the valve core. Besides, the optimized model has smaller lateral fluid force imposed on the valve core FL than the original model when the relative travel L/Lmax > 0.625, and they have close FL in the other range. Also, the optimized model has larger axial fluid force imposed on the valve core FA than the original model when L/Lmax > 0.875, and they have close FA in the other range.
{"title":"Fluid Dynamics Investigation on the Body Structure Inside a Sleeve Regulating Valve","authors":"Jia-yi Wu, Yang Yue, Jia-Ming Yang, Zhi-jiang Jin, J. Qian","doi":"10.1115/fedsm2020-20153","DOIUrl":"https://doi.org/10.1115/fedsm2020-20153","url":null,"abstract":"\u0000 The sleeve regulating valve is a typical flow regulating component, which is indispensable in various industrial applications. This work investigates the effects of the body structure on the overall performance and the flow characteristic of a sleeve regulating valve. The anterior cavity h, the diameter of the center cavity Dc, and the eccentricity of the center cavity e are studied in a parametric way. When the relative increment of h, Dc, and e all take the value of 0.15, the rated flow coefficient Kve of the optimized valve is promoted by 33.99% relative to the Kve of the original model. The optimized model presents less wear between the valve core and the sleeve relative to the original model. It results from the fact that the non-centrosymmetric pressure distribution is reduced on the valve core. Besides, the optimized model has smaller lateral fluid force imposed on the valve core FL than the original model when the relative travel L/Lmax > 0.625, and they have close FL in the other range. Also, the optimized model has larger axial fluid force imposed on the valve core FA than the original model when L/Lmax > 0.875, and they have close FA in the other range.","PeriodicalId":103887,"journal":{"name":"Volume 1: Fluid Applications and Systems; Fluid Measurement and Instrumentation","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127917459","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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