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Hydrodynamic experimental benchmark data of bubbly two-phase pipe flow around a semi-circular constriction
No full textFor the investigation of bubbly two-phase flow, which should serve as a future benchmark experiment for CFD code validation, an experimental study has been conducted at the Transient Two-Phase Flow (TOPFLOW) facility at Helmholtz-Zentrum Dresden – Rossendorf (HZDR) using ultrafast electron beam X-ray tomography (UFXRAY). In this study, flow constrictions were installed into a pipe to create a generic three-dimensional flow field as an advanced test case for CFD codes. UFXRAY provide valueable data of the gas phase dynamics with high temporal and spatial resolution.
The provided data set contains the entire results of the experimental series L30 that uses a semi-circular flow constriction with a blockage ratio of 0.5.
An additional info.txt file provides all required information (e.g. nomenclature or binary file structure) and is, thus, necessary for interpretation of the experimental data.This work is funded by the German Federal Ministry for Economic Affairs and Energy (BMWi) with the grant number 1501481 on the basis of a decision by the German Bundestag
Ultrafast X-ray tomography raw-data of bubbly two-phase pipe flow around a semi-circular constriction
No full textFor the investigation of bubbly two-phase flow, which should serve as a future benchmark experiment for CFD code validation, an experimental study has been conducted at the Transient Two-Phase Flow (TOPFLOW) facility at Helmholtz-Zentrum Dresden – Rossendorf (HZDR) using ultrafast electron beam X-ray tomography (UFXRAY). In this study, flow constrictions were installed into a pipe to create a generic three-dimensional flow field as an advanced test case for CFD codes. UFXRAY provide valueable data of the gas phase dynamics with high temporal and spatial resolution.
The provided data set contains tomography raw-data for the experimental series L30 that uses a semi-circular flow constriction with a blockage ratio of 0.5.
For visualization, the data might be opend with Fiji. Therefore choose Import->Raw... In the following window specify "Image type" as 16-bit Unsigned, "Width" as 288 pixels and "Height" as 500 pixels for 2x1000Hz measurement or 200 pixels for 2x2500Hz measurement. Make sure that "Little-endian byte order" is checked. A data set contains image frames of both scanning planes in alternating order. Therefore, if only a single scanning plane is required, the offset and gap parameters need to be set to 288000 bytes for 2x1000Hz measurement or 115200 bytes for 2x2500Hz measurement.This work is funded by the German Federal Ministry for Economic Affairs and Energy (BMWi) with the grant number 1501481 on the basis of a decision by the German Bundestag
Ultrafast X-ray tomography raw-data of bubbly two-phase pipe flow around a ring-shaped constriction
No full textFor the investigation of bubbly two-phase flow, which should serve as a future benchmark experiment for CFD code validation, an experimental study has been conducted at the Transient Two-Phase Flow (TOPFLOW) facility at Helmholtz-Zentrum Dresden – Rossendorf (HZDR) using ultrafast electron beam X-ray tomography (UFXRAY). In this study, flow constrictions were installed into a pipe to create a generic three-dimensional flow field as an advanced test case for CFD codes. UFXRAY provide valueable data of the gas phase dynamics with high temporal and spatial resolution.
The provided data set contains tomography raw-data for the experimental series L30 that uses a ring shaped flow constriction with a blockage ratio of 0.5.
For visualization, the data might be opend with Fiji. Therefore choose Import->Raw... In the following window specify "Image type" as 16-bit Unsigned, "Width" as 288 pixels and "Height" as 500 pixels for 2x1000Hz measurement or 200 pixels for 2x2500Hz measurement. Make sure that "Little-endian byte order" is checked. A data set contains image frames of both scanning planes in alternating order. Therefore, if only a single scanning plane is required, the offset and gap parameters need to be set to 288000 bytes for 2x1000Hz measurement or 115200 bytes for 2x2500Hz measurement.This work is funded by the German Federal Ministry for Economic Affairs and Energy (BMWi) with the grant number 1501481 on the basis of a decision by the German Bundestag
Hydrodynamic investigations of gas-liquid two-phase flow in centrifugal pumps - reconstructions (selected data)
No full textThis data repository contains reconstructed and quantitatively analyzed gas-liquid two-phase distributions obtained from a centrifugal pump mock-up whose geometry is related to a commercially available industrial centrifugal pump. As measurement system the ultrafast electron beam X-ray CT scanner (UFXCT) is applied with a frame rate of 2,500 Hz, single-plane mode and a total scanning interval of 5 seconds. The data repository contains:
Reconstructed raw data (FBP) sets for selected two-phase flow operating conditions at constant 1480 rpm with static and rotating impeller, respectively
Corresponding quantitative gas fraction data sets (for static impeller position)
Averaged gas fraction distributions
Standard deviations of the gas fraction mean values
Data evaluation scriptsThe Project was founded by the German Federal Ministry of Education and Research (BMBF) under the funding code 02NUK023
Gas-liquid two-phase flow in a centrifugal pump mock-up with swirling gas flow injection at 1300 rpm
No full textThis data repository contains reconstructed and quantitatively analyzed gas-liquid two-phase distributions obtained from a centrifugal pump mock-up whose geometry is related to a commercially available industrial centrifugal pump. As measurement system the ultrafast electron beam X-ray CT scanner (UFXCT) is applied with a frame rate of 2,500 Hz, single-plane mode and a total scanning interval of 5 seconds. The data repository contains:
Reconstructed raw data sets (Algebraic Reconstruction Technique from the UFO framework) for different inlet gas fractions (eps0.0xx) at constant 1300 rpm and for both rotating and back-rotated impeller positions, respectively
Extracted RPM per CT scan (frame) including its raw data
Extracted angular positions of the impeller mock-up per frame
Calculated quantitative gas fraction data sets (static impeller position)
Time-averaged gas fraction distribution and its corresponding averaged variance
Pump and impeller mask data
Additional data obtained from the SPS server with a sampling frequency of 1 HzData is stored in HDF5 format
Gas-liquid two-phase flow in a centrifugal pump mock-up with disperse gas flow injection at 1600 rpm
No full textThis data repository contains reconstructed and quantitatively analyzed gas-liquid two-phase distributions obtained from a centrifugal pump mock-up whose geometry is related to a commercially available industrial centrifugal pump. As measurement system the ultrafast electron beam X-ray CT scanner (UFXCT) is applied with a frame rate of 2,500 Hz, single-plane mode and a total scanning interval of 5 seconds. The data repository contains:
Reconstructed raw data sets (Algebraic Reconstruction Technique from the UFO framework) for different inlet gas fractions (eps0.0xx) at constant 1600 rpm and for both rotating and back-rotated impeller positions, respectively
Extracted RPM per CT scan (frame) including its raw data
Extracted angular positions of the impeller mock-up per frame
Calculated quantitative gas fraction data sets (static impeller position)
Time-averaged gas fraction distribution and its corresponding averaged variance
Pump and impeller mask data
Additional data obtained from the SPS server with a sampling frequency of 1 HzData is stored in HDF5 format
Gas-liquid two-phase flow in a centrifugal pump mock-up with disperse gas flow injection at 1480 rpm
No full textThis data repository contains reconstructed and quantitatively analyzed gas-liquid two-phase distributions obtained from a centrifugal pump mock-up whose geometry is related to a commercially available industrial centrifugal pump. As measurement system the ultrafast electron beam X-ray CT scanner (UFXCT) is applied with a frame rate of 2,500 Hz, single-plane mode and a total scanning interval of 5 seconds. The data repository contains:
Reconstructed raw data sets (Algebraic Reconstruction Technique from the UFO framework) for different inlet gas fractions (eps0.0xx) at constant 1480 rpm and for both rotating and back-rotated impeller positions, respectively
Extracted RPM per CT scan (frame) including its raw data
Extracted angular positions of the impeller mock-up per frame
Calculated quantitative gas fraction data sets (static impeller position)
Time-averaged gas fraction distribution and its corresponding averaged variance
Pump and impeller mask data
Additional data obtained from the SPS server with a sampling frequency of 1 HzData is stored in HDF5 format
Experimental Investigations on Bubbly Two-Phase Flow in a Constricted Vertical Pipe
Get PDFGas-liquid two-phase flows occur in many industrial applications and apparatuses. The design and optimization of such apparatuses and processes requires the numerical simulation of two-phase flows. However, two-phase flow simulations are still a challenging task, especially for industrial scales. Here, the simulation of large flow domains and high Reynolds number flows require a reduction of the resolved time-scales and length-scales by a high level of modeling to decrease the computational effort. Therefore, physics-based models are needed to depict the complex transport processes between the phases. Thus, two-phase flows are the object of ongoing research.
Up to now, the majority of closure models for turbulence, interfacial forces or bubble breakup and coalescence were validated against experimental data derived from experiments in simple flow channel geometries like straight pipes. Their application for the simulation of two-phase flows with three-dimensional flow structures like e.g. recirculating areas, flow separation or strong velocity gradients requires constant experimental validation and further development.
Hence, improved experimental methods are required for investigations of gas-liquid two-phase flows to provide reliable data for further development and validation of numerical flow simulation models. Therefore, experiments were performed in a constricted pipe under bubbly two-phase flow conditions. Three-dimensional flow structures were created by two types of flow constrictions for a variety of gas and liquid superficial velocities up to jg = 0.1400 m⋅s-1 and jl = 1.6110 m⋅s-1. The flow fields upstream and downstream of the flow constrictions were studied using ultrafast X-ray tomography and hot-film anemometry to obtain cross-sectional phase distribution, bubble characteristics and liquid velocity.
The analysis of the ultrafast X-ray tomography image data was significantly improved by development of a histogram-based gas holdup calculation. Furthermore, the spatial dependence of the axial image plane distance was studied to improve the determination of axial bubble velocities and, thus, bubble sizes. The experimental method was advanced by simultaneous application of ultrafast X-ray tomography and hot-film anemometry.
Eventually, the experimental data was compared to state-of-the-art Euler/Euler two-fluid simulations. The simulations were performed in the framework of a parallel doctoral thesis in the Experimental Thermal Fluid Dynamics department at the Helmholtz-Zentrum Dresden – Rossendorf by Ms. Sibel Tas-Koehler following the baseline approach. The results were compared in terms of the phase distribution, bubble sizes and gas velocity for two operating conditions using the homogeneous multiple size group model.Zweiphasenströmungen aus Gasen und Flüssigkeiten treten in vielen industriellen Anwendungen und Apparaten auf. Um einen sicheren, zuverlässigen und optimalen Betrieb einzelner Komponenten und gesamter Anlagen zu gewährleisten, sind die Strömungen Gegenstand zahlreicher Untersuchungen. Numerische Simulationen sind ein unverzichtbares Instrument, um Prozesse unter diesen Aspekten zu bewerten. Die Simulation von Zweiphasenströmungen, insbesondere im industriellen Maßstab, ist jedoch nach wie vor eine anspruchsvolle Aufgabe. Um den Rechenaufwand zu verringern und die Simulation von großen Strömungsgebieten und Strömungen mit hohen Reynoldszahlen zu ermöglichen, ist ein hohes Maß an Modellierung notwendig. Gleichzeitig wurden die meisten Schließungsmodelle zur Beschreibung von Turbulenz, Grenzflächenkräften oder Blasenzerfall und -koaleszenz für einfache Geometrien wie beispielsweise gerade Rohre entwickelt. Die Anwendung dieser Modelle für die Simulation von Zweiphasenströmungen mit dreidimensionalen Strömungsstrukturen, wie z.B. Rezirkulationsgebieten, Strömungsablösungen oder starken Geschwindigkeitsgradienten, erfordert eine ständige experimentelle Validierung und Weiterentwicklung. Dies wiederum erfordert eine immer höhere Auflösung der eingesetzten Messsysteme und steigende Qualität der experimentellen Daten.
Um verlässliche Daten für die Weiterentwicklung und Validierung von Modellen für die numerische Strömungssimulation zu erhalten sind daher verbesserte experimentelle Methoden zur Untersuchung von Gas-Flüssig-Strömungen erforderlich. Aus diesem Grund wurden Experimente an einer Blasenströmung in einem Rohr mit einer Strömungsverengung durchgeführt. Zwei Arten von Verengungen wurden genutzt, um dreidimensionale Strömungsstrukturen für eine Vielzahl von Betriebsbedingungen zu erzeugen. Diese sind durch Gas- und Flüssigkeitsleerrohrgeschwindigkeiten bis zu jg = 0.1400 m⋅s-1 und jl = 1.6110 m⋅s-1 definiert. Um die Phasenverteilung im Querschnitt der Strömung, Blaseneigenschaften und die Flüssigphasengeschwindigkeit stromauf- und -abwärts der Verengung zu ermittelt, wurde die Strömung mit Hilfe der ultraschnellen Röntgentomographie und Heißfilm-Anemometrie untersucht.
Die Datenanalyse für die Bilddaten der ultraschnellen Röntgentomographie wurde durch die Entwicklung einer Histogramm-basierten Gasgehaltsberechnung erheblich verbessert. Um die Bestimmung der axialen Blasengeschwindigkeiten und damit der Blasengrößen zu verbessern, wurde außerdem die räumliche Abhängigkeit des axialen Bildebenenabstands untersucht. Die experimentellen Methoden wurden durch die gleichzeitige Anwendung von ultraschneller Röntgentomographie und Heißfilm-Anemometrie weiterentwickelt.
Die experimentellen Daten wurden mit dem Stand der Technik von Euler/Euler-Zweiphasen-Simulationen verglichen. Die Simulationen wurden im Rahmen eines parallelen Promotionsvorhabens in der Abteilung Experimentelle Thermofluiddynamik am Helmholtz-Zentrum Dresden – Rossendorf von Frau Sibel Tas-Köhler durchgeführt und folgten der Baseline-Modell Strategie. Die Ergebnisse wurden unter Verwendung des homogenen Modells mehrerer Größenklassen bezüglich der Phasenverteilung, der Blasengrößen und der Gasgeschwindigkeit für zwei Betriebsbedingungen verglichen
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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