Anne K. Geppert

Anne K. Geppert
Universität Stuttgart · Institute of Aerospace Thermodynamics

Dr.-Ing.
Postdoctoral Researcher in DROPIT

About

21
Publications
5,974
Reads
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152
Citations
Citations since 2017
15 Research Items
149 Citations
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Introduction
Researcher in the field of multiphase flows, with specialisation in experimental and analytical droplet dynamics processes, i.e. droplet impact on solid, structured and wetted walls, and spray formation. Coordinator for all experimental work in international research training group DROPIT.
Additional affiliations
June 2019 - present
Universität Stuttgart
Position
  • PostDoc Position
Description
  • Postdoc. researcher for int. research training group "Droplet Interaction Technologies"-DROPIT. Development of exp. methods for micro-fluid dynamic research. Coordination of all experimental methods within DROPIT. Support/counselling of PhD-students.
January 2012 - June 2019
Universität Stuttgart
Position
  • Research Associate
Description
  • Experimental Investigation of Droplet Wall-Film Interaction of Binary Systems
Education
May 2014 - May 2014
Technische Universität Darmstadt
Field of study
  • LIDESP - International Advanced Course on Liquid Interfaces, Drops and Sprays
April 2008 - December 2011
Universität Stuttgart
Field of study
  • Aerospace Engineering
October 2005 - March 2008
Universität Siegen
Field of study
  • Mechanical Engineering

Publications

Publications (21)
Conference Paper
Full-text available
Droplet interaction technologies find application in a large number of industrial processes. Those applications show a strong non-linear coupling between flow dynamics and transport processes as well as the presence of multiple characteristic length and time scales. The International Research Training Group "Droplet Interaction Technologies" (GRK 2...
Conference Paper
Full-text available
Droplet impact on dry, structured surfaces is ubiquitous in nature and technology, e.g., in soil erosion, spray painting, anti-icing coatings or self-cleaning surfaces. These applications also depend on the wetting behaviour of the surface. To gain a better understanding of the complex interplay between surfaces structure and wettability, a single...
Article
Full-text available
An unsteady analytical solution is proposed to predict the spreading rate of the crown generated by an impacting droplet onto wetted walls. The modelling strategy is based on the direct integration of the boundary layer correction into the potential flow solution that leads to the well-established square-root time dependence. The original potential...
Article
Full-text available
We study the vertical impact of a droplet onto a cubic pillar of comparable size placed on a flat surface, by means of numerical simulations and experiments. Strikingly, during the impact a large volume of air is trapped around the pillar side faces. Impingement upon different positions of the pillar top surface strongly influences the size and the...
Article
Full-text available
Medical inhalers have been used for the treatment of a wide range of respiratory diseases including the COVID-19 pandemic. In this study, we investigate the annular liquid jet breakup with a coaxial supersonic gas jet using Large Eddy Simulations. This contributes a further understanding and improvement of medical inhaler designs. The liquid is suc...
Conference Paper
Full-text available
When a drop impacts onto a liquid film the outcome can differ very much and is in general difficult to parameterize due to the many influencing parameters. A parameter often idealized when studying drop film interactions is the shape of the impacting drop. Whereas for one-component interactions its influence on the impact outcome is known to some e...
Preprint
An analytical solution is proposed to predict the crown propagation, generated by a single droplet impact on wetted walls. This approach enables a smooth transition from the inertia-driven to the viscous-controlled regime of crown propagation. The modelling strategy is based on the stagnation-point flow, because it resembles closely the hydrodynami...
Chapter
Drop impact onto wetted surfaces is of relevance to any spray coating application since the maximum spreading diameter and the residual film thickness of the applied liquid droplets affect the efficient distribution of the coating materials. In this paper, we propose a modification to existing models for crown propagation during single drop impact...
Conference Paper
Drop impact on a dry/wetted wall is of relevance to many industrial applications as well as to natural sciences. For some applications, such as spray coating or icing of plane wings, both the maximum spreading diameter and the residual thickness of the wall film are of paramount importance for the efficient design and optimisation of the different...
Thesis
A variety of industrial applications depend on impact dynamics of droplets on liquid surfaces of a different fluid, e.g. fuel post-injection in diesel engines. Hereby, the injected fuel impacts directly on the oil-wetted cylinder wall. Thus, the oil’s lubrication performance is diminished and secondary droplets are ejected back into the combustion...
Article
The rapid implementation of Selective-Catalytic-Reduction (SCR) technologies into light passenger and commercial vehicles, led to the omission of fundamental research creating several reliability issues that are largely related to the research field of droplet dynamics. In this study, the splashing behavior of an AdBlue droplet impacting onto thin...
Conference Paper
Full-text available
The scenario of an impacting droplet onto a wall-film is highly relevant in many technical systems. In combustion engines, for example, the interaction of fuel drops with oil wall-films can alter the pollutant emissions. In order to make reliable predictions for these systems, it is of crucial importance to gain a deeper insight into the underlying...
Conference Paper
Full-text available
Liquid droplet impact on thin wall-films is encountered in a variety of scenarios. Even though there are numerous studies on liquid droplet interaction with wall-films of the same liquid (‘one-component’ interaction), very few studies have considered liquid droplets impacting on wall-films of a different liquid (‘two-component’ interaction). With t...
Article
Full-text available
The present paper investigates experimentally the impact dynamics of crown-type splashing for miscible two- and one-component droplet wall–film interactions over a range of Weber numbers and dimensionless film thicknesses. The splashing outcome is parametrised in terms of a set of quantifiable parameters, such as crown height, top and base diameter...
Conference Paper
Full-text available
Single drop impacts on thin liquid layers are of particular interest because of the ejection of secondary droplets, the so-called splashing. Only a few studies handle the deposition/splashing limit for two-component interaction, where the liquid properties of the impacting drop and wall film differ significantly. This study aims at identifying a un...
Conference Paper
Full-text available
The phenomenon of a single drop impact onto a thin liquid film (e.g. wall-film) is encountered over a wide range of natural and engineering applications. Among different drop impact morphologies, splashing has drawn great attention over the last decades due to its relatively complex morphology that is characterised by liquid fingers at the upper cr...
Article
This study presents an experimental and numerical investigation on the impact morphology and the onset of splashing for the interaction of a hexadecane drop with a thin wall-film of the same liquid. Experiments were carried out for Weber numbers between 300 and 1400 and a dimensionless film thickness between 0.1 and 0.5. The experimental and numeri...
Conference Paper
Full-text available
The present study investigates experimentally the impact morphology for permutations of the two-component system hyspin-hexadecane. The results of this study in terms of a model to predict the impact outcome, intends to improve the carbon footprint of Diesel engines. A comparative study is performed to highlight similarities (formation and ejection...
Conference Paper
Full-text available
In the present paper a first inside in the impact phenomenology of Hyspin droplets impacting on Hexadecane wall films is presented. The results of this study will be used to improve the carbon footprint of Diesel engines by the development of a model predicting the impact outcome. A comparative study is performed to highlight differences (formation...

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Projects

Projects (2)
Project
Understanding of physical mechanisms connecting small scale features and large scale flow dynamics and subsequent translation into more realistic physical models for detail processes, suitable for technical applications. Development of robust and accurate numerical tools capable of coupling small-scale features into macroscopic solvers for selected applications (e.g. two-phase simulations in porous media and on structured surfaces). Furthermore, DROPIT provides an excellent interdisciplinary qualification programme for Ph.D. students, to foster their development into independent researchers. Research Programme: TA-A: Droplet - Gas Interaction TA-B: Droplet - Wall Interaction TA-C Droplet - Liquid Interaction Further information and recent news are available at: https://www.project.uni-stuttgart.de/dropit/
Project
Understanding of droplet impact dynamics on walls covered with film of a different fluid