MPI Kolloquiumsreihe: Prof. Dr. Berend van Wachem

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MPI Kolloquiumsreihe: Prof. Dr. Berend van Wachem, On the behaviour of particles, droplets and interfaces - Studying the Small Scale Physics to Improve the Understanding of Large-Scale Processes

  • Datum: 08.02.2018
  • Uhrzeit: 16:00 - 17:00
  • Vortragender: Prof. Dr. Berend van Wachem
  • Lehrstuhl Mechanische Verfahrenstechnik, Otto-von-Guericke-Universität Magdeburg
  • Ort: Max-Planck-Institut Magdeburg
  • Raum: Großer Seminarraum "Prigogine"
  • Kontakt: sek-pcp@mpi-magdeburg.mpg.de

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On the behaviour of particles, droplets and interfaces - Studying the Small Scale Physics to Improve the Understanding of Large-Scale Processes

Abstract

Particles, Droplets and Fluid-Interfaces play a significant role in our daily lives; ranging from the living cells in our body, in rain or snow, in liquid or solid drugs, and in many processes in energy and manufacturing industries. The importance of understanding the behaviour of particles, droplets and interfaces is ever increasing, as we demand new generations of drugs, higher quality products, and more environmentally friendly processes.

During this talk, I will focus on two aspects of the fundamental behaviour of particles, droplets and interfaces: the interaction of particles (and droplets) with turbulence, and the behaviour of interfaces in falling films. In both cases, the micro-scale understanding and modelling has lead to a better understanding of the physics of the flow and such processes at the larger scales.

The interaction of particles with turbulence has for long been a topic of interest for predicting the behaviour of industrially relevant flows. This talk will investigate the behaviour of spheres, elongated axi-symmetric ellipsoidal particles, discs and fibers, and their interaction with turbulence, collisions between the particles, and the effects of the particles on turbulence in DNS of forced turbulence, and in two turbulent channel flows, one with low Re number and one with high Re number. A comprehensive modelling framework has been developed and has been applied to these gas-particle flows. An example of a snapshot is shown in Figure 1. A discussion of the results, from first principles will reveal a new mechanism for the exchange of energy between particles and the turbulence of the flow. It is also shows how this exchange of energy can, under certain conditions, lead to drag reduction. A case-study will be presented on how this understanding can be used to improve existing and help design new processes at the larger scale.

In the second part of the talk, I will discuss the modelling challenges and results from the interface behaviour in falling films. In these interfacial flows, the interplay of capillary and inertial effects can be harnessed to increase the performance of heat and mass exchange in microfluidic geometries, where flows are typically laminar. As an example, the dynamics of solitary waves on falling liquid films is discussed. A complex flow developing in the liquid films at intermediate Reynolds numbers leads to a saturation of the wave height, while the flow in the liquid film and the shape of the wave are directly coupled to each other. In fact, a simple scaling of the dominant mechanisms leads to a self-similar description of certain aspects of these solitary waves.