Tidlegare gjesteforelesninger og seminarer

The simulation of multi-phase fluids has attained growing interest in the last decades. While for single-phase flow with the Navier-Stokes system the basic model is well understood, for multi-phase systems additional challenges by the necessity to track the transition zones or interfaces between different fluid components arise. 
We propose to use a phase field as a smooth indicator function to describe this situation. Using phase-field models, one introduces a small layer of mixed fluids as a so-called diffuse interface. One benefit of phase-field models is, that they can naturally deal with topology changes and can easily be extended to cope with contact line dynamics.
This model allows for discussing the optimal control problem for two-phase flow. We introduce a thermodynamically consistent phase-field model for two-phase flow including a model for contact line dynamics and introduce an energy stable numerical scheme. 
This scheme allows us to investigate the time-discrete (open loop) optimal control problem, where we investigate different control actions to steer a given distribution of phases towards the desired distribution. We derive the existence of solutions to the optimal control problem and provide first-order optimality conditions.

Hybrid format via Zoom possible on demand (contact timokoch at uio.no)

Hardi Peter, Associate Professor at the Max-Planck-Institute for Solar Physics, University of Göttingen.

By Jeremy Swann from the Max Planck Institute of Immunobiology and Epigenetics, Freiburg, Germany. Open for all.

C*-algebra seminar by Marcelo Laca (University of Victoria)

Migration of particles and deformation and coalescence of droplets can be highly affected by the non-Newtonian properties of the carrier fluid. 
In this talk, we focus on the effects of viscoelasticity and yield stress (plasticity) on particle and droplet dynamics. Results are presented from numerical simulations of Navier-Stokes equations coupled with viscoelastic and elastoviscoplastic constitutive models. We will investigate how to yield stress and elasticity affect the final position of a particle in channel flows, and how complex fluid droplets deform, merge and jump on a superhydrophobic surface.

Hybrid format via Zoom possible on demand (contact timokoch at uio.no)

Til minne om Norges fremste astrofysiker og grunnlegger av Institutt for teoretisk astrofysikk, professor Svein Rosseland (1894 – 1985), arrangerer Institutt for teoretisk astrofysikk hvert år en Rosselandforelesning.

C*-algebra seminar talk by John Quigg (Arizona State University)

Brain source analysis is an important tool in brain research. It is used for example during operation planning for epilepsy patients. Given EEG (electroencephalography) and MEG (magnetoencephalography) measurements the goal is to reconstruct the brain activity, i.e. the electric potential in the brain. This poses an inverse problem. It was observed in experiments, that the accuracy of the inverse problem strongly depends on the quality of the forward simulation, in particular the head model. We discuss how modern numerical methods like discontinuous Galerkin (dG) methods and cut-cell techniques can increase the robustness of the forward problem and simplify the overall workflow. Hardware-oriented design of numerical methods allows for improved speed of the inverse simulation by making use of modern hardware resources. In order to compute the forward problem efficiently, we propose an algebraic multigrid solver for cut-cell dG methods. We introduce the challenges of EEG/MEG inverse modeling and discuss how different parts of the problem can be improved using modern numerical methods.

Hybrid format via Zoom possible on demand (contact timokoch at uio.no)

The talk will start at ca. 13:00 right after the talk by Andrea Bressan.

Welcome to our GEOHYD Lunch Seminar Friday 10th of May @ 12:15 in Aud. 2, Geology building or via videolink using Zoom. The seminar is helt by Diarmuid Corr, Lancaster University.

Abstract: Many constructions have been proposed to attain adaptivity within the IGA framework (HB-, T-, LR-splines among others).
The idea of all approaches is to break the tensor product structure of the space in order to allow a spatially varying resolution.
Here we present an approach for adaptivity in IGA aimed at solving PDEs with preconditioned Krylov methods. 
All the main ingredients of this work are already known, but their combination looks promising for the 
development of isogeometric solvers with a good balance of flexibility and computational efficiency.

Hybrid format via Zoom possible on demand (contact timokoch at uio.no)

Cristian Vignali, Physics and Astronomy Department, Bologna University (Italy)

C*-algebra seminar talk by Guillaume Aubrun (Université Claude Bernard Lyon 1)

About the speaker:

Irina Gribkovskaia is currently a Professor of Quantitative Logistics. She has a PhD in Differential Equations from the Belarusian State Uni- versity (1997). Prior to becoming a professor in 2008, Irina worked as an Associate Professor at the Faculty of Applied Mathematics, Be- larusian State University and at Molde University College. Her main research interests are mathematical modeling and optimization meth- ods for planning problems, planning under uncertainty, vehicle routing, and offshore energy logistics.

C*-algebra seminar talk by Alistair Miller (Queen Mary University of London)

By Quentin Mauvisseau from the Natural History Museum, University of Oslo

Abstract: Dynamic Contact Lines are moving lines at which two fluids (eg air and water) and a solid meet. They offer longstanding paradoxes in the theory of continuum mechanics. I describe some aspects of their computation: a curtain-coating numerical experiment, a withdrawing plate, and a droplet between parallel plates.  All computations are done using Volume-Of-Fluid methods on octree grids, and comparisons with phase field and molecular dynamics approaches performed in collaboration with KTH, Stockholm.

Hybrid format via Zoom possible on demand (contact timokoch at uio.no)

Welcome to our GEOHYD Lunch Seminar Friday 3th of June @ 12:15 in Aud. 2, Geology building or via videolink using Zoom. The seminar is helt by Dylan Mikesell, NGI.

Marianne Dahl, senior researcher at The Peace Research Institute Oslo (PRIO)

The Section 4 seminar for the Spring of 2022 will be held on Tuesdays from 10:15–12:00 (see the schedule)