De natuur heeft veel organismen uitgerust met intelligente tactieken om voedsel of soortgenoten te vinden. Chemische stoffen, afgescheiden door een bron, worden meegenomen door de stroming. Door de turbulente stroming wordt de wolk van deze stof snel verspreid, zodat slechts af en toe een flard van deze stof voorbij komt. Dit is echter voldoende voor de organismen om op efficiënte wijze de bron te vinden. Zoekstrategieën als deze kunnen ook voor mensen nuttig zijn: denk aan het snel kunnen opsporen van onderzeese lekkages met onderwaterrobots. In dit project willen we zo’n zoekstrategie, ‘infotaxis’ genaamd, toepassen op een eenvoudige 2D stroming. In een numerieke simulatie laat een bron regelmatig een tracer los die wordt meegevoerd door de stroming. Met de zoekstrategie wordt de bron zo snel mogelijk gelokaliseerd.
Rudie Kunnen, Herman Clercx
Contact: Rudie Kunnen
Benchmarking earthquake models (BSc)
Numerical studies on slip-stick faulting have until now depended on ad-hoc constitutive laws which for most cases are not known a-priori. A novel formulation based on the multicomponent Lattice Boltzmann method* has been developed to find a quantitative connection between the physics of complex soft-glassy materials below yield stress and the dynamics of stick-slip faulting events leading to earthquakes.
Synthetic earthquake catalogs are being generated from plastic events (stick-slip causing topological changes) occurring in a sheared emulsion of poly-disperse droplets, using an in-house code developed of the method mentioned above. The student will use tools of statistical physics to benchmark these catalogs against classical earthquake models like the 2D Burridge-Knopoff (BR) and cellular-automaton based Self Organized Criticality (SOC) –like models.
Pinaki Kumar, Federico Toschi
Contact: Federico Toschi
Levitate glowing droplets with ultrasound (BSc)
Project aim: To create and test a setup to levitate phosphorescent droplets using an acoustic levitator.
Studying liquid droplets is useful for a variety of applications, from evaporation to selfcontained reaction vessels, or even the breakup of droplets. It is difficult, however, to create a contactless environment for droplets. Levitation of droplets would allow a great boundary condition for any experiment. By using an ultrasound speaker in combination with a parallel reflector, it is possible to trap the droplet in the air with pressure waves through acoustic streaming. This relatively simple setup traps the droplet at zero-amplitude pressure nodes of the standing wave between the speaker and the reflector. What effect does this have on the droplet? Can the droplet be accurately positioned? How does an evaporating droplet phosphoresce? You can find out! By using high-speed cameras, high power lasers, and your own setup you will be able to investigate all the dynamics and intracacies of levitating droplets.
Statistical Crowd Dynamics (MSc)
In this area, a number of projects involve an exciting mixture of fundamental physics research and technological development. They are addressed to physics students interested in statistical physics at crossroads between fluid dynamics and social sciences and that are IT & computing enthusiasts willing to face state-of-the-art challenges. Crowd dynamics is a recent research topic aiming at understanding and modeling the coordinated behavior of walking pedestrians. Our investigations employ extensive, reallife, automatic pedestrian tracking through grids of overhead Microsoft Kinect sensors (cf. the figure). We pursue both real-time and offline analyses via ad hoc algorithms. It is our
ultimate aim to develop particle-like models whose dynamics reproduce in statistical sense our observations. The interest toward these models goes far beyond physics with relevance, e.g., in transport and safety engineering.
Alessandro Corbetta, Federico Toschi
Contact: Federico Toschi
Thermoelectrically magnetohydrodynamic (TEMHD) driven flows of electrically conducting fluids (BSc/MSc)
Temperature gradients in an electrically conducting fluid may give rise to an electric current (the Seebeck effect), which in combination with an externally imposed magnetic field gives rise to a Lorentz force that can drive a flow in the fluid. This pumping or stirring is of particular importance in industrial metallurgy and for liquid-metal flows in thermonuclear fusion reactors. Using a multiphysics approach this project aims to study the flow of a conducting fluid through TEMHD pumping incorporating also convection using numerical simulation. For that we adopt a two-dimensional model of a channel flow of a liquid metal that is exposed to an incoming heat flux. We are especially interested in the flows ability to carry off the incoming heat as well as the time scales that are associated with transient behaviour in the velocity field.
Contact: Leon Kamp
Ventilation flow (BSc/MSc)
Ventilation flows are important for keeping a healthy indoor environment by removing for example pollutants in an efficient way. One way to enhance the ventilation efficiency of such flows is by making them time-dependent. Recent computational fluid dynamics (CFD) simulations suggest that the air exchange efficiency for an enclosure that is ventilated by a time-varying in- and outflow can be much higher than for a steady ventilation flow. The present project (Bachelor or Master) aims to better understand enhanced ventilation efficiency for time-dependent flows using concepts from dynamical system theory combined with two-dimensional direct numerical simulation (DNS) of incompressible flows in a rectangular enclosure with an in- and an outflow opening.
Leon Kamp, GertJan van Heijst, Twan van Hooff (fac B)
Contact: Leon Kamp