David Konstantin Tilcher, F. Popescu, H. Sommer, L. Thamsen, P. Thamsen
As part of a collaborative research project (OPTIMA) by Fraunhofer FOKUS, Engineering Company Prof. Dr. Sieker mbH, Department of Distributed and Operating Systems and Department of Fluid System Dynamics, TU Berlin, an „Intelligent Pumping Station” is being developed. In this research project, the operation of wastewater pumping stations is to be optimized by integrating precipitation forecasts and recording operating conditions on one hand, and by integrating historical data on use and operation on the other. The individual strategies for optimizing the operation of pumping stations and the possibilities of data integration will be systematically investigated. The focus of this paper is on the method for developing an optimized pump control. It examines how knowledge of predicted inflow can be used to achieve energy savings and a reduction in wastewater overflows. This method is based on the development of an algorithm in which detailed consideration of pump specifics and future pumping station inflow can be used to predict all possible suction head level curves for the considered period of time. Depending on the target criterion — minimum energy consumption per transported cubic meter or minimum overflow volume — the algorithm calculates the optimum path from all possible suction chamber level curves.
{"title":"Control Optimization Through Prediction-Based Wastewater Management","authors":"David Konstantin Tilcher, F. Popescu, H. Sommer, L. Thamsen, P. Thamsen","doi":"10.1115/fedsm2021-65375","DOIUrl":"https://doi.org/10.1115/fedsm2021-65375","url":null,"abstract":"\u0000 As part of a collaborative research project (OPTIMA) by Fraunhofer FOKUS, Engineering Company Prof. Dr. Sieker mbH, Department of Distributed and Operating Systems and Department of Fluid System Dynamics, TU Berlin, an „Intelligent Pumping Station” is being developed. In this research project, the operation of wastewater pumping stations is to be optimized by integrating precipitation forecasts and recording operating conditions on one hand, and by integrating historical data on use and operation on the other. The individual strategies for optimizing the operation of pumping stations and the possibilities of data integration will be systematically investigated.\u0000 The focus of this paper is on the method for developing an optimized pump control. It examines how knowledge of predicted inflow can be used to achieve energy savings and a reduction in wastewater overflows. This method is based on the development of an algorithm in which detailed consideration of pump specifics and future pumping station inflow can be used to predict all possible suction head level curves for the considered period of time. Depending on the target criterion — minimum energy consumption per transported cubic meter or minimum overflow volume — the algorithm calculates the optimum path from all possible suction chamber level curves.","PeriodicalId":23636,"journal":{"name":"Volume 2: Fluid Applications and Systems; Fluid Measurement and Instrumentation","volume":"58 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90977849","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}
Turbulent heated and buoyant plumes have important applications in the atmosphere such as wildland fire plumes, volcanic plumes, and chemical plumes. The purpose of the study is to analyze the turbulence structures, and to understand the stages of the development of the starting turbulent plumes. For this purpose, data generated from an in-house Weather Research Forecast model coupled with Large-eddy simulation (WRF-bLES) with two-way feedback between the buoyant plume and the atmosphere developed has been used. The release of both dense gases (Co2, So2) and, buoyant gases (He, NH3, heated air) from a circular source at the bottom of the domain have been investigated. The simulations of the axisymmetric plume were performed at a high Reynolds number of 108. Vortex Identification methods were used to extract the Coherent structures and the large-scale features of the flow. The results have demonstrated that both the dense and the buoyant heated plumes with different initial characters exhibited universal characteristics and the development of the starting plumes occurred in four characteristic stages: Stage 1 is the plume acceleration stage, followed by stage 2 which corresponds to the formation of the head of the plume which grows spatially. Stage 3 is when the plume head is fully formed and the flow transitions to quasi-steady-state behavior. The final stage is the fully developed plume. The identification of the four-stage development of the plume in the neutral environment is the first step in studying the turbulent heated and buoyant plumes development in order to characterize realistic plumes and to quantify the extent of mixing at each of these stages. This work has important contributions to fundamental fluid dynamics of buoyant plumes with implications on forecasting the plume trajectory of smoke, wildland fire, and volcanic plumes.
{"title":"The Four Stage Development of Starting Turbulent Buoyant Plumes","authors":"T. Tran, Kiran Bhaganagar","doi":"10.1115/fedsm2021-65540","DOIUrl":"https://doi.org/10.1115/fedsm2021-65540","url":null,"abstract":"\u0000 Turbulent heated and buoyant plumes have important applications in the atmosphere such as wildland fire plumes, volcanic plumes, and chemical plumes. The purpose of the study is to analyze the turbulence structures, and to understand the stages of the development of the starting turbulent plumes. For this purpose, data generated from an in-house Weather Research Forecast model coupled with Large-eddy simulation (WRF-bLES) with two-way feedback between the buoyant plume and the atmosphere developed has been used. The release of both dense gases (Co2, So2) and, buoyant gases (He, NH3, heated air) from a circular source at the bottom of the domain have been investigated. The simulations of the axisymmetric plume were performed at a high Reynolds number of 108. Vortex Identification methods were used to extract the Coherent structures and the large-scale features of the flow. The results have demonstrated that both the dense and the buoyant heated plumes with different initial characters exhibited universal characteristics and the development of the starting plumes occurred in four characteristic stages: Stage 1 is the plume acceleration stage, followed by stage 2 which corresponds to the formation of the head of the plume which grows spatially. Stage 3 is when the plume head is fully formed and the flow transitions to quasi-steady-state behavior. The final stage is the fully developed plume.\u0000 The identification of the four-stage development of the plume in the neutral environment is the first step in studying the turbulent heated and buoyant plumes development in order to characterize realistic plumes and to quantify the extent of mixing at each of these stages. This work has important contributions to fundamental fluid dynamics of buoyant plumes with implications on forecasting the plume trajectory of smoke, wildland fire, and volcanic plumes.","PeriodicalId":23636,"journal":{"name":"Volume 2: Fluid Applications and Systems; Fluid Measurement and Instrumentation","volume":"43 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88060327","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}
Ultrasonic flow metering is one of flow measurement techniques applicable to low temperature environment. Unlike pipe provers or Coriolis mass flowmeters, ultrasonic flowmeters require waveguides in front of ultrasound sensors. The waveguides can prevent heat conduction from the ultrasound sensors to low temperature liquids, such as liquid nitrogen. The ultrasound sensors can maintain its piezoelectricity within the specified temperature ranges by thermal insulation of the waveguides. In this study, low temperature testing on a pair of ultrasound sensors was performed to see if ultrasound waves could be transmitted normally through liquid nitrogen. A flowmeter cell with diameter of 300 mm (equivalently, 12”) was used as a container for liquid nitrogen. Three pairs of ultrasound sensors were installed in the flowmeter cell. Fiber-optic sensors were also attached on its inner wall to measure the temperature of liquid nitrogen. As a result, ultrasound waves were successfully transmitted between a pair of ultrasound sensors by using a preamplifier. The fiber-optic sensors could measure the temperature of liquid nitrogen although the sensors were not calibrated by the reference temperature scale at KRISS.
{"title":"Low Temperature Testing of Ultrasound Sensors in Liquid Nitrogen","authors":"J. C. Chung, M. M. Lee, S. Chun, I. Yang","doi":"10.1115/fedsm2021-64577","DOIUrl":"https://doi.org/10.1115/fedsm2021-64577","url":null,"abstract":"\u0000 Ultrasonic flow metering is one of flow measurement techniques applicable to low temperature environment. Unlike pipe provers or Coriolis mass flowmeters, ultrasonic flowmeters require waveguides in front of ultrasound sensors. The waveguides can prevent heat conduction from the ultrasound sensors to low temperature liquids, such as liquid nitrogen. The ultrasound sensors can maintain its piezoelectricity within the specified temperature ranges by thermal insulation of the waveguides.\u0000 In this study, low temperature testing on a pair of ultrasound sensors was performed to see if ultrasound waves could be transmitted normally through liquid nitrogen. A flowmeter cell with diameter of 300 mm (equivalently, 12”) was used as a container for liquid nitrogen. Three pairs of ultrasound sensors were installed in the flowmeter cell. Fiber-optic sensors were also attached on its inner wall to measure the temperature of liquid nitrogen. As a result, ultrasound waves were successfully transmitted between a pair of ultrasound sensors by using a preamplifier. The fiber-optic sensors could measure the temperature of liquid nitrogen although the sensors were not calibrated by the reference temperature scale at KRISS.","PeriodicalId":23636,"journal":{"name":"Volume 2: Fluid Applications and Systems; Fluid Measurement and Instrumentation","volume":"16 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87422598","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}
The pulsating flow conditions which a turbocharger turbine is exposed cause important deviations of the turbine aerodynamic performance when compared to steady flow conditions. Indeed, the secondary flows developing in the turbine are determined by the inflow aerodynamic conditions, which largely vary during the pulse cycle. In this paper, a high-resolved Large Eddy Simulation is performed to investigate and characterize the flow field evolution in a turbocharger radial turbine over the pulse cycle. At first, the model is validated against experimental results obtained in gas-stand flow conditions. Then, the instantaneous flow field at the rotor mid-span section is compared to the one given by the equivalent cycle-averaged steady flow conditions. The results highlight five distinct flow features. At low mass flow rates, when the relative inflow angle assumes large negative values, the flow separates at the blade pressure side, causing a secondary flow consisting in two counter-rotating vortices characterized by a diameter comparable to the blade passage. As the mass flow rate increases, the first vortex persists at the blade tip while the second one moves closer to the blade trailing edge. This corresponds to the second characteristic flow field. With increasing relative inflow angle, for the third characteristic flow feature, only the recirculation at the blade leading edge is displayed and its size gradually reduces. For the fourth characteristic flow feature, at moderate negative values of the relative inflow angle, the flow field is well aligned with the blade profile and free of secondary flows. Then, as the relative inflow angle gradually grows towards large positive values, the flow separates on the blade suction side causing the mixing of the flow with the stream flowing on the pressure side of the previous blade.
{"title":"Large Eddy Simulations of a Turbocharger Radial Turbine Under Pulsating Flow Conditions","authors":"R. Mosca, S. Lim, M. Mihăescu","doi":"10.1115/fedsm2021-65704","DOIUrl":"https://doi.org/10.1115/fedsm2021-65704","url":null,"abstract":"\u0000 The pulsating flow conditions which a turbocharger turbine is exposed cause important deviations of the turbine aerodynamic performance when compared to steady flow conditions. Indeed, the secondary flows developing in the turbine are determined by the inflow aerodynamic conditions, which largely vary during the pulse cycle.\u0000 In this paper, a high-resolved Large Eddy Simulation is performed to investigate and characterize the flow field evolution in a turbocharger radial turbine over the pulse cycle. At first, the model is validated against experimental results obtained in gas-stand flow conditions. Then, the instantaneous flow field at the rotor mid-span section is compared to the one given by the equivalent cycle-averaged steady flow conditions. The results highlight five distinct flow features. At low mass flow rates, when the relative inflow angle assumes large negative values, the flow separates at the blade pressure side, causing a secondary flow consisting in two counter-rotating vortices characterized by a diameter comparable to the blade passage. As the mass flow rate increases, the first vortex persists at the blade tip while the second one moves closer to the blade trailing edge. This corresponds to the second characteristic flow field. With increasing relative inflow angle, for the third characteristic flow feature, only the recirculation at the blade leading edge is displayed and its size gradually reduces. For the fourth characteristic flow feature, at moderate negative values of the relative inflow angle, the flow field is well aligned with the blade profile and free of secondary flows. Then, as the relative inflow angle gradually grows towards large positive values, the flow separates on the blade suction side causing the mixing of the flow with the stream flowing on the pressure side of the previous blade.","PeriodicalId":23636,"journal":{"name":"Volume 2: Fluid Applications and Systems; Fluid Measurement and Instrumentation","volume":"39 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80810416","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 potential way to reduce cooling system noises generated by heavy construction machines is to generate the required cooling airflow with a low fan speed, and one way to accomplish this is to optimize the ventilation path through which the airflow generated by the cooling fan must travel. However, while the computational fluid dynamics (CFD) approach would be effective for modeling the three-dimensional (3D) pressure drop characteristic of such systems, there have been few reports aimed at clarifying the loss generation mechanisms or suggesting minimization methods based on flow field viewpoints. Accordingly, in this study, we visualize the 3D flow field characteristics of an electric cooling fan system installed within the cooling enclosure of a heavy construction machine and investigate the details of the system’s pressure drop mechanisms. Our results confirm that airflow pressure declines in areas other than the radiator account for more than half of the reduced pressure experienced by the whole system. Additionally, we found that, in the exhaust side enclosure, pressure drops increased because the exhaust port outlet shapes were not optimized to the annular airflow of the cooling fan. Most notably, we found that in the region before reaching the exhaust port outlets, the airflow from the fan repeatedly collides with obstacles within the enclosure, thus producing stagnation and turbulence that exacerbates pressure drops before being expelled into the outside environment.
{"title":"Pressure Drop Mechanisms Generated in a Cooling System Enclosure of Construction Machinery","authors":"T. Kawano, M. Fuchiwaki","doi":"10.1115/fedsm2021-65578","DOIUrl":"https://doi.org/10.1115/fedsm2021-65578","url":null,"abstract":"\u0000 A potential way to reduce cooling system noises generated by heavy construction machines is to generate the required cooling airflow with a low fan speed, and one way to accomplish this is to optimize the ventilation path through which the airflow generated by the cooling fan must travel. However, while the computational fluid dynamics (CFD) approach would be effective for modeling the three-dimensional (3D) pressure drop characteristic of such systems, there have been few reports aimed at clarifying the loss generation mechanisms or suggesting minimization methods based on flow field viewpoints. Accordingly, in this study, we visualize the 3D flow field characteristics of an electric cooling fan system installed within the cooling enclosure of a heavy construction machine and investigate the details of the system’s pressure drop mechanisms.\u0000 Our results confirm that airflow pressure declines in areas other than the radiator account for more than half of the reduced pressure experienced by the whole system. Additionally, we found that, in the exhaust side enclosure, pressure drops increased because the exhaust port outlet shapes were not optimized to the annular airflow of the cooling fan. Most notably, we found that in the region before reaching the exhaust port outlets, the airflow from the fan repeatedly collides with obstacles within the enclosure, thus producing stagnation and turbulence that exacerbates pressure drops before being expelled into the outside environment.","PeriodicalId":23636,"journal":{"name":"Volume 2: Fluid Applications and Systems; Fluid Measurement and Instrumentation","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90112713","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}
G. Papadopoulos, D. Bivolaru, N. Martin, Timothy Dawideit
When voltage is applied between two electrodes situated in close proximity to each other (10–100 μm), a weakly ionized, low temperature plasma discharge can be generated. This in turn creates a plasma sheath, an electrically ionized boundary layer (typically of the order of 10’s to 100’s of microns), where space charge effects dominate. The sheath acts like a virtual capacitor, with the plasma behaving as an inductor. Aerodynamic effects influence the plasma morphology (shape, thickness), thus making the plasma the transduction mechanism. The attraction to the use of plasma discharge as a transduction method for fluid flow property measurement stem from the fact that it lends itself to a probe implementation that is simple in design, can be miniaturized, and at the same time offers unmatched capability for handling ultra-high temperature environments. Sensing plasma discharge characteristics and their variation due to flow interaction can be done electrically, but also optically to yield time-varying intensity and spectral information from fluid-plasma interaction. The current paper focuses on the deployment of a micro-plasma sensor system as a new novel multi-parameter sensing approach for surface flow measurement. Results on pressure dynamics, shear flow, and other possible engineering parameters will be discussed in the context of results from several bench-level experiments.
{"title":"Boundary Layer Multi-Property Flow Measurements Using a Micro-Plasma Sensor","authors":"G. Papadopoulos, D. Bivolaru, N. Martin, Timothy Dawideit","doi":"10.1115/fedsm2021-65560","DOIUrl":"https://doi.org/10.1115/fedsm2021-65560","url":null,"abstract":"\u0000 When voltage is applied between two electrodes situated in close proximity to each other (10–100 μm), a weakly ionized, low temperature plasma discharge can be generated. This in turn creates a plasma sheath, an electrically ionized boundary layer (typically of the order of 10’s to 100’s of microns), where space charge effects dominate. The sheath acts like a virtual capacitor, with the plasma behaving as an inductor. Aerodynamic effects influence the plasma morphology (shape, thickness), thus making the plasma the transduction mechanism. The attraction to the use of plasma discharge as a transduction method for fluid flow property measurement stem from the fact that it lends itself to a probe implementation that is simple in design, can be miniaturized, and at the same time offers unmatched capability for handling ultra-high temperature environments. Sensing plasma discharge characteristics and their variation due to flow interaction can be done electrically, but also optically to yield time-varying intensity and spectral information from fluid-plasma interaction. The current paper focuses on the deployment of a micro-plasma sensor system as a new novel multi-parameter sensing approach for surface flow measurement. Results on pressure dynamics, shear flow, and other possible engineering parameters will be discussed in the context of results from several bench-level experiments.","PeriodicalId":23636,"journal":{"name":"Volume 2: Fluid Applications and Systems; Fluid Measurement and Instrumentation","volume":"2006 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83039798","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}
Yijie Wang, Ang Li, G. Jensen, Jun Chen, Haiyan Zhang
With the increased demand for developing renewable energy, hydro energy has attracted more attention since it is reliable and easy to acquire. In this area, the cycloidal turbine has been recently studied and applied to ocean energy for its stable and efficient output. Compared to the ordinary vertical/horizontal axis turbine with fixed pitch angle blades (e.g., Darrieus turbine), the cycloidal turbine can maximize the extracted power efficiency by keeping the optimized angle of attack for the blades. Meanwhile, the cycloidal turbine provides a potential solution to solve the problems of self-starting and seasonal flow variations. Introducing an augmentation duct is considered as a method to further increase the incoming flow velocity of the turbine. Inspired by the design of the wind tunnel, a convergent-divergent design of the augmentation duct is developed. One is noted that the dimensions of the augmentation duct are essential to the performance of the duct. In this study, a convergent-divergent augmentation duct is developed based on a 3-blade cycloidal hydro-turbine, operated at a 2 m/s river. Computational fluid dynamic (CFD) analysis with sliding unstructured mesh is applied to investigate the extent how the dimensions of the duct affect the flow velocity to the turbine as well as the extracted power efficiency.
{"title":"Performance Optimization for Cycloidal Hydrokinetic Turbine With Augmentation Duct for Harvesting Riverine Energy","authors":"Yijie Wang, Ang Li, G. Jensen, Jun Chen, Haiyan Zhang","doi":"10.1115/fedsm2021-65753","DOIUrl":"https://doi.org/10.1115/fedsm2021-65753","url":null,"abstract":"\u0000 With the increased demand for developing renewable energy, hydro energy has attracted more attention since it is reliable and easy to acquire. In this area, the cycloidal turbine has been recently studied and applied to ocean energy for its stable and efficient output. Compared to the ordinary vertical/horizontal axis turbine with fixed pitch angle blades (e.g., Darrieus turbine), the cycloidal turbine can maximize the extracted power efficiency by keeping the optimized angle of attack for the blades. Meanwhile, the cycloidal turbine provides a potential solution to solve the problems of self-starting and seasonal flow variations. Introducing an augmentation duct is considered as a method to further increase the incoming flow velocity of the turbine. Inspired by the design of the wind tunnel, a convergent-divergent design of the augmentation duct is developed. One is noted that the dimensions of the augmentation duct are essential to the performance of the duct. In this study, a convergent-divergent augmentation duct is developed based on a 3-blade cycloidal hydro-turbine, operated at a 2 m/s river. Computational fluid dynamic (CFD) analysis with sliding unstructured mesh is applied to investigate the extent how the dimensions of the duct affect the flow velocity to the turbine as well as the extracted power efficiency.","PeriodicalId":23636,"journal":{"name":"Volume 2: Fluid Applications and Systems; Fluid Measurement and Instrumentation","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87449898","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 inline holography (DIH), as a three-dimensional (3D) measurement technique, is widely used in characterizations of the particles, droplets or bubbles under different multi-phase flow circumstances. By analyzing the phase information carried by the interference pattern, the reconstruction of shape and the location of a test target is then achieved. However, such reconstruction mechanism produces different levels of uncertainty between the in-plane (the plane parallel to the hologram plane) direction and out-of-plane (the plane normal to the hologram plane) direction, and the uncertainty of the latter is larger than the former. Also, the reconstruction algorithm fails when the interference patterns of some sections of the target are overlapped on the hologram since the overlapped patterns are merged into a pure shadow which doesn’t carry any phase information. This paper tested a method, the Multi-view Digital Inline Holography (MvDIH), that combines the holograms recorded from multiple views to overcome the addressed defects of the single view DIH. This technique uses the similar setup as the DIH but applies a different post-process method to implement the reconstruction. As the DIH is applied to each view, one can not only acquire the cross-section of the target in the hologram plane but also the outline of such cross-section in the space. Then, two reconstruction methods with different ideologies are developed as, the one based on the outline and the one based on the cross-section. A post-process algorithm is developed to realize these two reconstruction methods with the holograms recorded from different views. To evaluate the performance of the Multi-view DIH, a test model which imitates the droplet and liquid ligament structure is 3D printed and measured by the proposed method. The results demonstrate that, with only three view, both method provides limited reconstruction result. When comparing to the true test model, for the outline based method, some parts of the reconstructed model are missing and some details are merged into one piece with simple geometry. Yet, for the cross-section based method, the reconstructed model contains redundant parts which also make such result unsatisfied. As the used holograms are increased to six views, the reconstructed result for cross-section based method is approaching to the true model, but still some sections are reconstructed with certain level of ambiguity.
{"title":"Shape Reconstruction of Liquid Ligaments and Droplets Model via Multi-View Digital Inline Holography","authors":"W. Shang, Mateo Gomez, T. Meyer, Jun Chen","doi":"10.1115/fedsm2021-65861","DOIUrl":"https://doi.org/10.1115/fedsm2021-65861","url":null,"abstract":"\u0000 Digital inline holography (DIH), as a three-dimensional (3D) measurement technique, is widely used in characterizations of the particles, droplets or bubbles under different multi-phase flow circumstances. By analyzing the phase information carried by the interference pattern, the reconstruction of shape and the location of a test target is then achieved. However, such reconstruction mechanism produces different levels of uncertainty between the in-plane (the plane parallel to the hologram plane) direction and out-of-plane (the plane normal to the hologram plane) direction, and the uncertainty of the latter is larger than the former. Also, the reconstruction algorithm fails when the interference patterns of some sections of the target are overlapped on the hologram since the overlapped patterns are merged into a pure shadow which doesn’t carry any phase information. This paper tested a method, the Multi-view Digital Inline Holography (MvDIH), that combines the holograms recorded from multiple views to overcome the addressed defects of the single view DIH. This technique uses the similar setup as the DIH but applies a different post-process method to implement the reconstruction. As the DIH is applied to each view, one can not only acquire the cross-section of the target in the hologram plane but also the outline of such cross-section in the space. Then, two reconstruction methods with different ideologies are developed as, the one based on the outline and the one based on the cross-section. A post-process algorithm is developed to realize these two reconstruction methods with the holograms recorded from different views. To evaluate the performance of the Multi-view DIH, a test model which imitates the droplet and liquid ligament structure is 3D printed and measured by the proposed method. The results demonstrate that, with only three view, both method provides limited reconstruction result. When comparing to the true test model, for the outline based method, some parts of the reconstructed model are missing and some details are merged into one piece with simple geometry. Yet, for the cross-section based method, the reconstructed model contains redundant parts which also make such result unsatisfied. As the used holograms are increased to six views, the reconstructed result for cross-section based method is approaching to the true model, but still some sections are reconstructed with certain level of ambiguity.","PeriodicalId":23636,"journal":{"name":"Volume 2: Fluid Applications and Systems; Fluid Measurement and Instrumentation","volume":"22 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90864201","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}
Thermowells with helical strakes are becoming promising to prevent them from fatigue fracture by Kármán vortex street. Many studies suggest various kinds of measurement techniques, including strain rate measurement, acceleration measurement, and high-speed visualization to evaluate the role of Kármán vortex street to the flow-induced vibration. Nevertheless, use of laser Doppler vibrometry has not yet been reported in the literature. This study compared the tip deflection of a thermowell due to the flow-induced vibration by using the laser Doppler vibrometry and the strain rate measurement. The laser Doppler vibrometry could measure the tip deflection directly. On the other hand, the strain rate measurement had to convert the strain rate into the tip deflection through the Euler-Bernoulli beam theory. Measurement equivalence between the laser Doppler vibrometry and the strain rate measurement was discussed with the results of tip deflections of the thermowell.
{"title":"Use of Laser Doppler Vibrometry for Measuring Flow-Induced Vibration of a Thermowell in a Pipe Flow","authors":"S. Chun, Sibok Lee, Hyewon Yoon","doi":"10.1115/fedsm2021-64609","DOIUrl":"https://doi.org/10.1115/fedsm2021-64609","url":null,"abstract":"\u0000 Thermowells with helical strakes are becoming promising to prevent them from fatigue fracture by Kármán vortex street. Many studies suggest various kinds of measurement techniques, including strain rate measurement, acceleration measurement, and high-speed visualization to evaluate the role of Kármán vortex street to the flow-induced vibration. Nevertheless, use of laser Doppler vibrometry has not yet been reported in the literature. This study compared the tip deflection of a thermowell due to the flow-induced vibration by using the laser Doppler vibrometry and the strain rate measurement. The laser Doppler vibrometry could measure the tip deflection directly. On the other hand, the strain rate measurement had to convert the strain rate into the tip deflection through the Euler-Bernoulli beam theory. Measurement equivalence between the laser Doppler vibrometry and the strain rate measurement was discussed with the results of tip deflections of the thermowell.","PeriodicalId":23636,"journal":{"name":"Volume 2: Fluid Applications and Systems; Fluid Measurement and Instrumentation","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80081638","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}
Lamia Gaied, M. Lippert, L. Keirsbulck, F. Aloui, Emna Berrich
In this work, we propose an experimental study of the effect of surface roughness of the internal cylinder Couette-Taylor system in order to investigate the hydrodynamic instabilities of the flow. During experiments, the inner cylinder, which presents a rough surface with u cylinder corrugations, rotates at a given angular speed and the outer cylinder, which is smooth, is kept fixed. The main objective of the study is to demonstrate the effect of geometric parameters on the flow (the shape of the roughness). Experimental results have shown that the shapes of the surface irregularities have an effect on the appearance of the first instabilities, which strongly depend on the size, shape and nature of the roughness. In fact, the nature of surface roughness not only affects the friction on the wall, but also strongly influences the transport of mass and momentum in a given flow regime. The flow therefore evokes more friction when the inner (rotating) cylinder has a rough surface. This friction, which slows the speed of the fluid particles, strongly depends on the surface nature in contact with the fluid. The movement of the particles in these irregularities will therefore, be damped as a function of the shape of the roughness. In addition, the results also showed that once Couette-Taylor vortices are present, surface roughness can promote continued flow disturbance. The resulting flow then becomes less slow in the troughs of surface irregularities; thus, leads to less friction.
{"title":"Experimental Investigations on the Effect of a Wavy Surface on Hydrodynamic Instabilities in a Taylor-Couette System","authors":"Lamia Gaied, M. Lippert, L. Keirsbulck, F. Aloui, Emna Berrich","doi":"10.1115/fedsm2021-65631","DOIUrl":"https://doi.org/10.1115/fedsm2021-65631","url":null,"abstract":"\u0000 In this work, we propose an experimental study of the effect of surface roughness of the internal cylinder Couette-Taylor system in order to investigate the hydrodynamic instabilities of the flow. During experiments, the inner cylinder, which presents a rough surface with u cylinder corrugations, rotates at a given angular speed and the outer cylinder, which is smooth, is kept fixed.\u0000 The main objective of the study is to demonstrate the effect of geometric parameters on the flow (the shape of the roughness). Experimental results have shown that the shapes of the surface irregularities have an effect on the appearance of the first instabilities, which strongly depend on the size, shape and nature of the roughness. In fact, the nature of surface roughness not only affects the friction on the wall, but also strongly influences the transport of mass and momentum in a given flow regime. The flow therefore evokes more friction when the inner (rotating) cylinder has a rough surface. This friction, which slows the speed of the fluid particles, strongly depends on the surface nature in contact with the fluid. The movement of the particles in these irregularities will therefore, be damped as a function of the shape of the roughness. In addition, the results also showed that once Couette-Taylor vortices are present, surface roughness can promote continued flow disturbance. The resulting flow then becomes less slow in the troughs of surface irregularities; thus, leads to less friction.","PeriodicalId":23636,"journal":{"name":"Volume 2: Fluid Applications and Systems; Fluid Measurement and Instrumentation","volume":"40 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87168089","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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