Practical trainings, student assistants and theses

Understanding the behaviour of fibre-laden drops is critical due to their presence in various industrial applications, including microelectronics fabrication, portable medical devices, and biofuel production. Our work focuses on the numerical simulation of fibre-laden drops, specifically investigating a single long deformable fibre within a drop impacting a solid substrate. The study aims to elucidate the dynamic interactions between the fibre and the drop. Key objectives include determining the changes in drop dynamics due to the fibre and observing fibre deformation upon impact.

This work will involve computational fluid dynamics (CFD), particularly finite volume methods, with a focus on interface tracking using the Volume of Fluid approach. The simulation will incorporate surface wettability to enhance our understanding of elasto-capillary interactions, offering insights relevant to real-world applications.

We are seeking a motivated student with prior experience in CFD (preferably OpenFOAM) or similar modelling software.

• Enrolled in a degree program such as Process Engineering, Mechanical Engineering, or Computational Modelling and Simulation
• Strong interest in particle-fluid dynamics and numerical simulations
• Preliminary experience in CFD, ideally with OpenFOAM
• Basic coding skills, preferably in C++

• Immediate start possible
• Duration of internship or thesis as per university regulations
• Remuneration available, scholarship holders (e.g. ERASMUS+) are welcome

Computational fluid dynamics (CFD) is increasingly offering an alternative to experimental optimisation and improvement of both existing and new industrial processes or products, for which otherwise costly and time-consuming test and pilot plants are used. While the simulation of single-phase flows allows stable and reliable predictions, such numerical analyses for multiphase flows have so far only been validated and useful for selected cases due to their complexity and the large number of additional interactions.

In order to extend the applicability of numerical multiphase simulations, the Institute of Fluid Dynamics at the Helmholtz Centre Dresden-Rossendorf carries out experimental and numerical investigations in bubble columns in collaboration with the Institut de Mécanique des Fluides de Toulouse (IMFT) to better understand phase interaction phenomena. The current project focuses on the lateral lift force acting on millimetre-sized bubbles rising through a shear field, with particular interest in the influence of curved shear layers.

The objective of the proposed bachelor or master thesis is to performed direct numerical simulations at IMFT, Toulouse of well controlled configurations of a bubble (spherical or deformed) rising in a shear flow. The simulations will be compared against experiments performed at HZDR.

• Studies related to fluid dynamics (e.g. mechanical or process engineering, physics etc.)
• Experience in numerical simulation
• Good English or French language skills

• Working in a multidisciplinary and international team
• Place of work: IMFT in Toulouse
• Start: from March 2025
• Duration: approx. 6 months

Flowing foam is relevant to many different industrial applications, such as froth flotation in mineral processing, fire-extinguishing systems, or brewing beer and beverage production. In a scientific context, the rheological properties of foams are very complex and significantly different from those of Newtonian fluids such as water. As a result, despite numerous experimental and theoretical studies, the fluid dynamics of foams remain poorly understood.

This project focuses on a classical benchmark experiment: the flow around a cylindrical obstacle. To identify key parameters of flowing foam in this configuration, we use two unique radiographic measurement techniques. First, neutron radiography provides imaging measurements of the local liquid fraction of the flowing foam. Second, X-ray radiography with foam-tailored tracer particles allows to perform local velocity measurements in the flowing foam.

The following subtasks are mainly to be worked on:

• Assistance in preparing and performing the foam flow experiment in the X-ray laboratory at HZDR
• Analysis of the measurement data, including image processing and machine learning if applicable
• Documentation of the experiment and measurement results in written form

• Field of study: process engineering, fluid mechanics, or similar focus in chemistry or physics
• Experience with laboratory work, imaging measurement techniques or measurement data analysis is beneficial (e.g. using ImageJ, Matlab, Python)
• High motivation and interest in the subject
• Careful, structured and independent way of working
• Good oral and written communication skills in English or German
• Enjoyment of scientific work

• Working in a multi-disciplinary and international team
• Place of work: HZDR or TU Dresden
• Start: from January 2025
• Duration: min. 3 months
• Remuneration according to HZDR internal regulations

The development of a multi-channel flow body sensor according to patent WO 2010/069307 A1 aims to quantify the gas content in flow-carrying components. A decisive advantage of this sensor lies in its optical measuring principle, which is based on fiber-optic coupling and the analysis of the light output signal. This avoids electrical potentials in the measuring area, offering significant advantages over electrical measuring methods (intrinsic safety), especially for explosive mixtures.

Preliminary tests at the Institute for Experimental Fluid Dynamics at the Helmholtz Center Dresden-Rossendorf on gas-liquid flows showed that a clear binarization of the sensor output signal can be achieved due to the capillary effects in narrow channels and the different refractive indices of the gas and liquid phases. Building on previous work with a single-channel sensor prototype based on a polymer optical fiber (POF) with a diameter of 1 mm, the following tasks must be completed as part of further research.

Tasks:

• Adjusting the POF diameter to 1.5 mm in the single-channel configuration.
• Conducting experimental investigations of the new single-channel prototype using the already developed test system and evaluation programs.
• Designing a multi-channel sensor body for gas content measurements in the system.
• Developing a transition adapter to optimize the flow distribution between the DN10 flow pipe and the sensor body.

• Students majoring in fields such as process engineering, mechanical engineering, or chemical engineering.
• Interest in fluid mechanics and the development of measurement technology.
• Experience with 3D CAD tools.
• Basic knowledge of Python programming

Start date: 01.01.2025
Duration: according to the respective study regulations