The following speakers will be speaking at our symposium. Click on their names to find out more about them!

NB: The order of speaking might be subject to change

Speaker 1: Detlef Lohse

Speaker 2: Olga Shishkina

Speaker 3: Sander Huisman

Speaker 4: Kathrin Smetana

Speaker 5: GertJan van Heijst

Speaker 6: Richard Stevens

Speaker 7: Roberto Verzicco

Speaker 8: Fulvio Scarano

## Our speakers:

### Detlef Lohse

#### Biography

Detlef Lohse studied physics at the Universities of Kiel & Bonn (Germany), and got his PhD at Univ. of Marburg (1992). He then joined Univ. of Chicago as postdoc. After his habilitation (Marburg, 1997), in 1998 he became Chair at Univ. of Twente in the Netherlands and built up the Physics of Fluids group. Since 2015 he is also Member of the Max Planck Society and of the Max-Planck Institute in Göttingen and since 2017 Honorary Professor at Tsinghua Univ., Bejing.

Lohse’s present research interests include turbulence and multiphase flow, micro- and nanofluidics (bubbles, drops, inkjet printing, wetting), and granular & biomedical flow. He does both fundamental and more applied science and combines experimental, theoretical, and numerical methods.

Lohse is Editor of J. Fluid Mech. and Ann. Rev. Fluid Mech. (among others journals) and serves as Member at Large of the Executive Board of DFD. He is Member of the (American) National Academy of Engineering (2017), of the Dutch Academy of Sciences (KNAW, 2005), the German Academy of Sciences (Leopoldina, 2002) and Fellow of APS (2002). He won various scientific prizes, among which the Spinoza Prize (NWO, 2005), the Simon Stevin Meester Prize (STW, 2009), the Physica Prize of the Dutch Physics Society (2011), the AkzoNobel Science Award (2012), two European Research Council Advanced Grants (2010 & 2017), the George K. Batchelor Prize (IUTAM, 2012), the APS Fluid Dynamics Prize (2017), the Balzan Prize (2018), and the Max Planck Medal (2019). In 2010, he got knighted to become “Ridder in de Orde van de Nederlandse Leeuw”.

Website: http://pof.tnw.utwente.nl

#### Abstract

Professor Lohse will give a short introduction to the field of turbulence which will connect to all the talks of the other speakers during this day.

### Olga Shishkina

#### Biography

Olga Shishkina studied mathematics at the Lomonosov Moscow State University until 1987. In 1990 she received her doctorate in scientific computing from the Moscow University for Telecommunication & Informatics. After being a senior lecturer at Rybinsk Aviation Technological Academy until 1994, she worked as a researcher at the Lomonosov Moscow State University until 2002 and at the DLR Göttingen until 2014. In 2009 she habilitated in fluid mechanics at the TU Ilmenau and in 2014 also in mathematics at the University of Göttingen. In 2014 she became Heisenberg fellow and joined the MPIDS where she leads this independent group.

#### Abstract

We will discuss turbulent flows that occur from the inhomogeneity of the imposed temperature boundary conditions at the surfaces of a fluid layer. These turbulent natural convection flows are usually studied by examples of Rayleigh-Benard convection, vertical convection or horizontal convection. We will discuss the different setups and the corresponding experimental, numerical and theoretical investigations of these flows. Here we will focus on the global flow dynamics, the structures of the boundary layers and on the scaling relations for the mean heat and momentum transport, measured, respectively, by the Nusselt and Reynolds numbers, with the input parameters of the convection systems, which are represented by the Rayleigh and Prandtl numbers as well as by the geometrical characteristics of the fluid layer.

### Sander Huisman

#### Biography

Sander Huisman obtained his doctorate cum laude in 2014 on the topic of Turbulent Taylor- Couette flow in the Physics of Fluids group under the guidance of Prof. Dr. Chao Sun and Prof. Dr. Detlef Lohse. His expertise is in the field of experimental fluid dynamics, having worked on Taylor-Couette facilities, water channels, Rayleigh-Bénard convection cells, Hele-Shaw cells, and the Lagrangian Exploration Module. He was also involved in the construction of various turbulence setups. His interest is not only in single phase flows but also multiphase flows, the Lagrangian statistics of inertial inclusions, flows with phase-transitions, and heat, mass, and momentum transfer in turbulent flows.

#### Abstract

Experimental Measurement Techniques for Turbulent Flows

Flow rates have been measured thousands of years ago. Last two centuries our knowledge of fluid dynamics has exploded, and to verify our hypotheses, novel measurements techniques were invented last centuries. Recently, with the invent of the transistor, modern integrated circuits, and nanofabrication, the fields of high-speed cameras and laser technology have flourished, allowing experimentalists unprecedented access to flow properties. This talk will be about common measurement techniques used in the field of turbulence and the recent advancements of sensor technology. An overview of several common measurement techniques and their fundamental working principle will be discussed.

### Kathrin Smetana

#### Biography

Kathrin Smetana is an Assistant Professor at the Department of Applied Mathematics at the University of Twente. Prior to that appointment she worked as a postdoctoral associate in the Group of Prof. Dr. Mario Ohlberger in the Department of Applied Mathematics at the University of Münster, Germany and in the Group of Prof. Dr. Anthony T. Patera in the Department of Mechanical Engineering at the Massachusetts Institute of Technology, United States. Kathrin Smetana holds a PhD in Mathematics from the University of Münster. Recently she received the Professor De Winter Award for a publication on randomized multiscale methods. The main focus of her research is multiscale methods and model reduction for partial differential equations and randomized algorithms for numerical simulations.

#### Abstract

In the last decades numerical simulations based on partial differential equations (PDEs) have significantly gained importance in engineering applications, life sciences, or environmental sciences. However, many applications take place at multiple scales or exhibit rough coefficients, making a straightforward approximation of the underlying system of PDEs by discretization schemes such as the finite element or spectral element method often prohibitive. Multiscale methods that pass (local) knowledge on the fine-scale behavior of the solution of the PDE to the macro-scale solver have been developed to tackle these heterogeneous problems. In this talk, we will show how randomized methods, which have been applied very successfully in the context of data analysis, compressed sensing, and deep learning, can be used to derive efficient and rigorous multiscale methods.

### GertJan van Heijst

#### Biography

GertJan van Heijst is professor of fluid dynamics at Eindhoven University of Technology. His research interests include the dynamics of flows in rotating and stratified fluids, in particular vortex flows and turbulence in such fluid systems.

#### Abstract

Large-scale geophysical flows are characterized by the occurrence of vortex structures on a variety of scales. Examples are the atmospheric high- and low-pressure cells, tornadoes, but also tidal vortices in tidal-exchange flows between estuaries and the open sea. Such vortices may play an important role in the transport of material, such as sediment. In the lecture we will consider a few special geophysical flow configurations, with attention to the numerical and laboratory-scale modeling of the vortex flows arising. In particular, attention will be given to the transport of sediment by vortices, as occurring in the tidal-exchange flows in harbours and estuaries.

### Richard Stevens

#### Biography

Dr. Richard Stevens graduated cum laude in applied physics at the University of Twente (UT) in 2008 after 4 years and 7 months. In 2011 he obtained his doctorate, cum laude after 3 years and 3 months, in applied physics in the Physics of Fluids group for his study on Rayleigh-Bénard turbulence working with Prof. Lohse (UT) and Prof. Clercx (University of Eindhoven). In 2012 he obtained a FOM-YES! Fellowship to study wind farm dynamics using large eddy simulations at the John Hopkins University in the USA with Prof. Meneveau and Prof. Gayme. In 2016, he started as a tenure tracker at the University of Twente. In the same year, he obtained a Shell-NOW/FOM tenure track grant and an NWO VIDI grant to set up his research line on wind farm simulations at the UT. In 2018 he obtained an ERC Starting Grant to study ultimate thermal convection using high performance direct numerical simulations. He is also a partner in a Horizon 2020 collaboration on high-performance computing for wind energy.

#### Abstract

Similar to other renewable energy sources, wind energy is characterized by a low power density. Hence, for wind energy to make considerable contributions to the world’s overall energy supply, large wind farms (on- and offshore) consisting of arrays of ever larger wind turbines are being envisioned and built. From a fluid mechanics perspective, wind farms encompass turbulent flow phenomena occurring at many spatial and temporal scales. Of particular interest to understanding mean power extraction and fluctuations in wind farms are the scales ranging from 1 to 10 m that comprise the wakes behind individual wind turbines, to motions reaching 100 m to kilometers in scale, inherently associated with the atmospheric boundary layer. In this presentation, we discuss the state-of-the-art understanding of these flow phenomena (particularly mean and second-order statistics) through field studies, wind tunnel experiments, large-eddy simulations, and analytical modeling, emphasizing the most relevant features for wind farm design and operation.

### Roberto Verzicco

#### Biography

Roberto Verzicco is professor of fluid mechanics at the University of Rome “Tor Vergata” and part-time professor at the Physics of Fluids group of the University of Twente. Since 1993 he has published more than 180 scientific papers in international journals and 3 review papers.

His research interests include: turbulence, biofluidmechanics, complex industrial flows, and numerical methods for fluid mechanics. In 2005 he won the Frenkiel Award from the American PhyscalSociety and in 2012 the Wim Nieupoort Award for Scientific Computing. He is EUROMECH Fellow since 2012 and APS Fellow since 2013.

#### Abstract

The human heart pumps blood throughout the body bringing oxygen and nutrients to every cell and removing its waste. The heart achieves this fundamental goal by beating approximately 10^5 times per day to deliver a continuous flow rate of about 5 l/min with an outstanding reliability. This is possible thanks to the synchronized and synergistic action of the electrophysiology, mechanics of the tissues and hemodynamics that allow the heart of an adult human to operate on a power of only 8 W, lifelong. In this talk we will illustrate and discuss how the blood vortical structures and turbulence, generated in the heart chambers, make this possible through the multi-way coupled interactions with the other systems.

### Fulvio Scarano

#### Biography

Fulvio Scarano graduated in Aerospace Engineering at University of Naples (1996). Obtained the Ph.D. in 2000 (von Karman Institute, Theodor von Karman prize) and joined TU Delft at the faculty of Aerospace Engineering in the Aerodynamics Section during the same year.

Full professor of Aerodynamics, he currently heads the AWEP department (Aerodynamics, Wind Energy, Flight Performance and Propulsion) and acts as Deputy Dean of Aerospace Engineering.

Recipient of Marie-Curie grant (1999), Dutch Science Foundation VIDI grant (2005) and of European Research Council grants (ERC-StG, 2009; ERC-PoC 2016).

European project coordinator (EU-FP7 AFDAR, Advanced Flow Diagnostics for Aeronautical Research, 2010-2013). Supervised and promoted more than 30 PhDs.

Research interests cover the development of particle image velocimetry (PIV) and its applications to high-speed aerodynamics in the supersonic and hypersonic regime including turbulent flow phenomena. Specific contribution to the field of experimental aerodynamics are the upscale of Particle Image Velocimetry to face the challenges posed by industrial aerodynamics; development of the iterative image deformation technique, Tomographic PIV for 3D flow velocity measurements and its use to quantitatively determine pressure fluctuations and acoustic emissions in wind tunnel experiments. Recent works have dealt with the combination of PIV data with the constitutive laws of fluid motion “pouring space in time and vice versa”. Coordinator of the TU Delft multidisciplinary research group on Personal Air Mobility.3

#### Abstract

Turbulence is omnipresent in Nature and for a multitude of engineering flow systems. The modern aircraft is no exception.

The aerodynamic behavior of aircraft systems is strongly influenced by turbulence, from the scale of the atmospheric boundary layer to that of the minute oscillations bursting across wings.

The lecture gives a survey about the controversial role of turbulence: beneficial in some cases, when accelerating vortex wake decay, or enhancing fuel mixing during combustion. Turbulence is the “necessary evil” to delay unwanted flow separation at wings.

In many other cases, turbulence is avoided, delayed or mitigated by all possible means: if laminar flight is constantly aimed at with flow control technologies, what can be done about atmospheric turbulence at scales larger than the aircraft more than fastening the seatbelt ?