# Guest lectures by Professor Dr.-Ing. Milovan Perić and Professor Dr. Hans Kuerten

## Time

15.02.2019 kl. 09.30 - 12.00

## Description

There will be two guest lectures on February 15, 2019 prior to the PhD defence of Anders Schou Simonsen

### TITLE

Sources of Errors in Numerical Simulations, Their Interaction and Assessment

### GUEST LECTURER

Professor Dr.-Ing. Milovan Perić

### TIME

9:30 - 11:00

### ABSTRACT

Numerical solutions of fluid flow and related phenomena are (or may be) affected by various kinds of errors. There are three kinds of systematic errors which cannot be avoided: (i) iteration errors, because we never solve the algebraic equation systems exactly; (ii) discretization errors, because we are solving discrete approximations of the mathematical model on finite grids; (iii) modeling errors, because the mathematical model is not exact (e.g. due to turbulence model, cavitation model, etc.). Programming and user errors are in principle avoidable but usually also present. When solving engineering problems, it is important to analyze the contribution of various error components and be able to give a reliable estimate of the accuracy of solution. This is not a simple task, because the equations being solved are highly non-linear and errors from different sources influence each other: they may augment, but also partially cancel each other. The presentation will focus on identifying common sources of error, discussing the interaction of some error kinds, estimating the errors and especially on the effects of grid quality on various errors.

### About the lecturer

Milovan Perić studied mechanical engineering in Sarajevo, Bosnia and Herzegovina, and graduated in 1980. He continued with postgraduate studies at Imperial College, London, where he obtained PhD-degree in 1985. He then worked as a research assistant and lecturer at the University of Erlangen from 1986 to 1991, visiting scholar at Stanford University in 1992 and as professor for fluid dynamics at the Institute of Ship building in Hamburg from 1993 to 2001. From 2002 to 2013 he has worked for the software-company CD-adapco (since 2016 taken over by Siemens) and held the positions of Director of Product Development, Director of Technology and Vice President for Technology. Since January 2014 he leads a consulting company CoMeT -Continuum Mechanics Technologies GmbH and acts as a consultant to Siemens Industry Software GmbH. In 2016 he became faculty member (without employment contract) at the Faculty of Engineering, University of Duisburg-Essen, where he teaches Applied CFD and supervises master and PhD research projects in the Institute of Ship Technology, Ocean Engineering and Transport Systems. He has published around 200 papers on CFD and related subjects and is a co-author of a popular book on this subject (published by Springer in several languages).

and

### Title

Particle-laden Flow

### Guest Lecturer

Prof. Dr. Hans Kuerten

### Time

11:00 - 12:00

### Abstract

In many applications in industry and in nature, particle or droplet transport in turbulent flow plays a role. Examples are combustion of fuel particles (biomass or metal) and cloud formation. In our group we study methods and models for accurate simulations of particle- and droplet-laden turbulent flow. In the presentation I will discuss two topics which we investigate.

In order to separate different kinds of plastic particles from a waste stream, recently the magnetic density separation system has been developed. In this system plastic particles are introduced in a ferromagnetic fluid. Under the influence of a magnetic field the effective mass density of the fluid depends on position and the particles move to their equilibrium position. In order to optimize this technique, we perform numerical simulations of the motion of these particles and in particular investigate the effects of particle collisions on the separation efficiency.

For particles larger than the smallest scale of turbulence, point-particle methods are inaccurate due to the use of correlations for the drag force which only hold if particles are sufficiently small. A way to improve these correlations is by particle-resolved DNS. We used this method in turbulent flow in a channel with an array of particles to determine optimal values for the coefficients in a correlation for the drag force. The use of this optimal correlation in point-particle DNS results in better agreement with the results for the particle-resolved simulation.

### About the lecturer

Prof. Hans Kuerten graduated with honors in Theoretical Physics at Utrecht University in 1983. He received his PhD in Physics in 1987 on thermodynamic and hydrodynamic properties of liquid Helium mixtures. After that he worked until 1998 as an assistant professor in the Department of Applied Mathematics at the University of Twente and subsequently as an associate professor at the Department of Mechanical Engineering at Eindhoven University of Technology, where he became full professor in Computational Multiphase Flow in 2014. Since 2010 he is also part-time professor at the University of Twente. Since 1987 he investigated numerical methods and models for various types of flows, ranging from compressible turbulent flows around airplanes to evaporating micro-scale droplets on porous substrates and particle-laden turbulent flows.

He is the local director of the Dutch Research School for Fluid Mechanics J.M. Burgerscentrum in Eindhoven and a member of the organizing committee of the DLES workshop series. He was visitor of several universities, for example Politecnico di Torino, Helmut Schmidt University, Hamburg and ETH Zurich.

### THE GUEST LECTUREs WILL TAKE PLACE IN PON 105, room 3.115, AND ALL ARE WELCOME

### Host

Department of Energy Technology

### Address

Pontoppidanstræde 105, room 3.115