Practical trainings, student assistants and theses

CFD analysis of the bubbly flow in a vertical pipe with an obstacle (Id 294)

Student practical training / Bachelor theses / Master theses

Foto: Zweiphasige Umströmung von Hindernissen - reference picture ©Copyright: Martin Neumann-KippingFor the CFD modelling of bubbly flows at the component-scale the two-fluid methodology has proven to be the most effective approach. For the various interfacial forces, turbulence sources and bubble-bubble interactions a multitude of partly empirical closure models exist in the literature, each validated with the data from a particular experiment conducted for a specific flow configuration. For many years the HZDR strategy is to establish a fixed set of closure models that reflects local flow phenomena and offers generality and predictability [1]. The current set of baseline models was established via the CFD analysis of numerous validation cases.
The set of baseline models should now be applied to new TOPFLOW data for bubbly flows, which were recently generated at the HZDR [2]. For the polydisperse flow in a constricted vertical pipe quantities such as gas holdup distributions, liquid velocities and bubble sizes were measured. The goal of the project is to reproduce these new cases with the CFD-software OpenFOAM. A main challenge will be the generation of a suitable computational mesh for the pipe geometry with a ring-shaped and a baffle-shaped obstacle. The obstacles constrict the flow locally creating turbulent wake regions that cause interesting bubble-bubble interactions. The polydisperse CFD analysis of the case will allow the detailed analysis of the bubble coalescence and breakup processes and the evaluation of the models that aim to describe them.

References:

[1] R. Rzehak et al., "Unified modeling of bubbly flows in pipes, bubble columns, and airlift columns," Chem. Eng. Sci. 157, pp. 147-158, 2017.
[2] M. Neumann-Kipping et al., "Investigations on bubbly two-phase flow in a constricted vertical pipe," Int. J. Multiph. Flow 130, 2020.

Main tasks:

  • Creating a suitable geometry and mesh of the constricted pipe
  • Establishing a corresponding polydisperse case setup in OpenFOAM
  • Comparison of computed results with measured TOPFLOW data
  • Parameter variation of the established setup (via various liquid and gas superficial velocities, different obstacle shapes)
  • Report and presentation of results

Department: Computational Fluid Dynamics

Contact: Dr. Hänsch, Susann

Requirements

  • Experience using CFD software, preferably OpenFOAM
  • Excellent written and verbal communication skills in English
  • Team player with a strong interest in multiphase flows

Conditions

Duration: 6 months

Links:

Online application

Please apply online: english / german

Druckversion


Development of an autonomous underwater flow tracking sensor (Id 293)

Master theses / Diploma theses / Compulsory internship

Foto: flow following sensor particle ©Copyright: Dr. Sebastian ReineckeData acquisition in large industrial vessels such as biogas fermenters or wastewater treatment plants is limited to local measurement points due to limited access to the vessel and the non-transparency of the fluid. To optimize these kinds of vessels, the three-dimensional flow field and the spatial distribution of fluid properties such as temperature and electrical conductivity inside the vessel must be known. This can be achieved by the autonomous flow -following sensor particles developed by the HZDR. Equipped with a pressure sensor, an accelerometer, two gyroscopes and a magnetometer, the sensor particle can track the movement inside the vessels and derive the flow field from that. The sensor particle also feature an actuating buoyancy control unit. For the investigation of smaller vessels a smaller version of the sensor particle is needed. The objective of this master thesis is to hard- and software develop, manufacturing and test of a miniature flow tracking sensor. This includes the following tasks, based on the existing multi-parameter sensor concept:

  • Picking a suitable microcontroller (MC) to perform the data acquisition
  • Design of the schematic and layout of the printed circuit board which includes the above mentioned sensors, a battery with a wireless charging concept, data storage on an SD-card
  • Design the casing
  • Assemble the board and the casing
  • Implementing the data acquisition on the MC
  • Test the sensor particle in a lab scale vessel

Department: Experimental Thermal Fluid Dynamics

Contact: Buntkiel, Lukas

Requirements

  • Studies in electrical engineering, mechatronics, mechanical engineering and similar engineering courses
  • Experience in programming microcontrollers for embedded systems (e.g. STM32)
  • Experience in board design for embedded systems

Links:

Online application

Please apply online: english / german

Druckversion


6-month internship on the experimental investigation of granular mixing (Id 285)

Student practical training / Bachelor theses / Master theses / Diploma theses / Compulsory internship / Volunteer internship

Background:
Granular mixing is an important industrial process. In the pharmaceutical industry for instance, the powder that is pressed to make tablets is produced by mixing precise quantities of active substances and excipients in granular state. The mixing needs to be done in such a way that the final powder has a homogeneous composition. Tablets may also need to be coated in a pan coater. Granular mixing also plays a crucial role there, as it greatly affects the thickness of the coating. Granular mixing is also often coupled with heat exchanging and solid-gas or solid-solid reactions, as is the case of rotary kilns in the cement, ceramics and metallurgical industries. The quality of the mixing is then a crucial factor to the efficiency of the overall process.

Objectives:
The objective of the work is to experimentally study the mixing process of two different types of granular particles inside a rotating drum under various operating conditions. More specifically, the mixing process is to be captured with a high-speed camera. The videos are then to be post-processed in order to extract characteristics of the particle velocity fields and mixing efficiency. The mixing facility is already available.

Tasks:

  • Literature survey
  • Mixing experiments under various operating conditions
  • Post-processing of the results with MATLAB

Department: Experimental Thermal Fluid Dynamics

Contact: Papapetrou, Theodoros Nestor

Requirements

  • Student of natural sciences or engineering
  • Willingness to conduct experimental work

Conditions

Duration: 6 months
Remuneration: available

Online application

Please apply online: english / german

Druckversion


Contributions to motion tracking of autonomous flow-following sensor particles in industrial process environments (Id 279)

Bachelor theses / Master theses / Diploma theses / Compulsory internship

Foto: AutoSens_StirredReactor ©Copyright: fwdf (Mailgruppe)Data acquisition in large industrial vessels such as biogas fermenters or wastewater treatment plants is limited to local measurement points due to limited access to the vessel and the non-transparency of the fluid. To optimize these kinds of plants, the three-dimensional flow field and the spatial distribution of properties such as temperature and electrical conductivity inside the vessel need to be known. This can be achieved by the autonomous flow-following sensor particles developed by HZDR. Equipped with a pressure sensor, an accelerometer, two gyroscopes and a magnetometer, the sensor particle can track the movement inside the vessels and to infer the flow field from that. The analysis of the data is done after a successful recovery from the vessel. Therefore, algorithms of any complexity can be used to track the motion of the sensor particle.

For the extension and especially for the improvement of the motion tracking we offer the following tasks, from which we can agree on a topic for a thesis or an internship:

  • Development of motion tracking algorithms
  • Characterization and error correction of the sensors
  • Intelligent sampling for the sensors
  • Experimental investigation of the maximal acceleration on a stirrer
  • Development of firmware to cover several data acquisition scenarios
  • Development of an end-user program for the configuration and data analysis of the gathered data

Department: Experimental Thermal Fluid Dynamics

Contact: Buntkiel, Lukas

Requirements

Studies in the area of electrical, mechatronic, mechanical engineering or similar

  • Basics of measurement uncertainty, digital signal processing
  • Data analysis in Python
  • Independent and structured way of working

Conditions

Start possible at any time
Duration according to the respective study regulations

Links:

Online application

Please apply online: english / german

Druckversion


Design and operation of liquid metal batteries as large-scale storage option (Id 256)

Student practical training / Bachelor theses / Master theses / Diploma theses / Compulsory internship / Volunteer internship

Foto: Study of a liquid metal battery module ©Copyright: Dr. Michael Nimtz, ©Michael NimtzIn contrast to conventional batteries, Liquid Metal Batteries feature all liquid anodes (alkaline or alkaline earth metal), cathodes (transition metal or metal) and electrolytes (molten salts) at a temperature between 400 °C and 600 °C. For the operation of liquid metal batteries as large-scale storage option (frequency control and other applications), the design of the storage system and operation strategies (including a battery management system) need to be implemented and tested using exemplary load curves.
Starting point is an existing model of a battery system in Python.

Note: This is an offer suitable for a bachelor, master or diploma thesis or studentic internships.
Do not apply if you already finished your studies!

Department: Magnetohydrodynamics

Contact: Dr. Nimtz, Michael

Requirements

Study of mechanical engineering, physics, mathematics or similar
Basic knowledge of engineering principles.
Good knowledge of a programming language, preferably python.

Conditions

Start: October 2019
Duration: 4-6 months
Paid according to HZDR-internal tariff

Links:

Online application

Please apply online: english / german

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Bestimmung von Geschwindigkeitsfeldern aus tomographischen Bilddaten mittels Kreuzkorrelation (Id 164)

Bachelor theses / Master theses / Diploma theses

Foto: ROFEX CAD ©Copyright: Dr. Frank BarthelAm Institut für Fluiddynamik am Helmholtz-Zentrum Dresden-Rossendorf sind zahlreiche Messverfahren für die Untersuchung von Mehrphasenströmungen entwickelt worden. Eines davon ist die ultraschnelle Elektronenstrahl-Röntgen-Computertomographie, welche mit Aufnahmeraten von bis zu 8000 Bildern pro Sekunde eine dedizierte Aufklärung von Strömungsstrukturen erlaubt. Aufgrund der quasi simultanen Aufnahme von Bilddaten aus zwei Messebenen ergibt sich zudem die Möglichkeit, axiale Geschwindigkeiten zu bestimmen, wofür üblicherweise Kreuzkorrelationsverfahren verwendet werden. Im Rahmen dieser Arbeit sollen die Möglichkeiten dieser Methodik in Hinblick auf die Bestimmung von Geschwindigkeitsfeldern in verschiedenen Strömungsszenarienn analysiert werden.

Folgende Teilaufgaben sind zu lösen:

  • Studie zu verschiedenen Varianten der Kreuzkorrelation
  • Simulation verschiedener Szenarien und Bewertung der Genauigkeit
  • Übertragung der Ergebnisse auf reale Messungen

Department: Experimental Thermal Fluid Dynamics

Contact: Dr. Bieberle, Martina

Requirements

  • Studium der Informatik, Mathematik oder einer Ingenieurwissenschaft
  • Interesse an Messverfahren und Datenanalyse
  • Selbständiges Arbeiten

Conditions

Bearbeitungszeit 4 bis 6 Monate

Links:

Online application

Please apply online: english / german

Druckversion


Untersuchung des Einflusses von Regularisierungsmethoden auf Bildrekonstruktionsalgorithmen (Id 57)

Student practical training / Bachelor theses / Master theses / Diploma theses

Bei der tomographische Bildrekonstruktion muss ein diskretes inverses Problem gelöst werden, wofür algebraische Methoden wie zum Beispiel ART und CG-Verfahren verwendet werden können. Dabei spielt die Regularisierung, die den Einfluss von Diskretisierungsfehler und Messdatenrauschen auf die Lösung beschränkt, eine entscheidende Rolle. Deren Einfluss auf die Bildrekonstruktion von Röntgen- und Gamma-CT-Messdaten soll untersucht werden. Dazu sind folgende Teilaufgaben zu lösen:

  • Implementierung verschiedener Regularisierungsmethoden
  • Anwendung der Programme auf Messdaten
  • Parameterstudien um die Regularisierungsmethoden für die Messdatensätze zu optimieren.

Department: Experimental Thermal Fluid Dynamics

Contact: Dr. Wagner, Michael, Dr. Bieberle, Martina

Requirements

  • Programmierkenntnisse in MATLAB
  • Grundkenntnisse zur numerischen Behandlung linearer Gleichungssysteme

Links:

Online application

Please apply online: english / german

Druckversion