Events - Page 16

Doctoral candidate Matthias Rauter at the Department of Mathematics, Faculty of Mathematics and Natural Sciences, is  defending the thesis Multiphase Navier-Stokes Equations applied to landslide tsunamis: Numerical simulations of granular flows and their interaction with water bodies for the degree of Philosophiae Doctor.

C*-algebra seminar talk by Magnus Goffeng

Abstract: In computational mechanics, high fidelity simulations of a parameterized partial differential equation (PDE) are often computational expensive, which make them impractical for real-time predictions. Non-intrusive reduced order modelling aims to address this problem with a fast low rank approximation. This is usually done in two phases: the model is built in the offline phase and the prediction is done in the online phase. In the offline phase, data points, or so-called snapshots, are collected from simulations or measurements. The reduced basis space can then be obtained from the dataset using Proper Orthogonal Decomposition. In the online phase, the solution for a new set of parameters is obtained by first recovering the expansion coefficients for the reduced basis and then projecting them back into the uncompressed real-life space. The non-intrusive approach relies on a statistical mapping between the coefficients and the parameters. Various methods have been proposed to do so, this seminar will discuss radial basis function interpolations and dynamic mode decompositions.

This talk is part of the Mechanics Lunch Seminar series. That means 20min talks plus discussion in an informal setting.

Zoom: To obtain the Zoom meeting details please contact Timo Koch (timokoch at math.uio.no).

May12 is a joyful opportunity for the mathematical community to celebrate women in mathematics. The celebration takes place every year, all around the world. Please join us!

C*-algebra seminar talk by Ulrich Pennig

Abstract: Graphics processing units, or GPUs, offer significantly increased performance for some scientific computing workloads. But in the case of finite element simulations on unstructured meshes, the benefits of using GPUs are still the subject of an ongoing discussion for which there is no clear conclusion. We describe our work on improving the GPU acceleration of a finite element solver framework called FEniCS, where code is automatically generated for the user from a high-level description of their finite element problem. We use automated code generation to offload the assembly of linear systems to a GPU, while taking care that data transfers between CPU and GPU do not become a performance bottleneck. We provide examples to show that GPUs and automated code generation can be used to accelerate finite element solvers. Even though more work is needed to find efficient GPU-based linear solvers, our improvements to FEniCS can be used as a starting point for exploring the potential of GPU acceleration for finite element simulations.

This talk is part of the Mechanics Lunch Seminar series. That means 20min talks plus discussion in an informal setting.

Zoom: To obtain the Zoom meeting details please contact Timo Koch (timokoch at math.uio.no).

C*-algebra seminar talk by Rufus Willett

Doctoral candidate Reyna Guadalupe Ramirez de la Torre at the Department of Mathematics, Faculty of Mathematics and Natural Sciences, is  defending the thesis Experiments on Bubble and Droplet Production in Falling Jets and Breaking Waves for the degree of Philosophiae Doctor.

Abstract:Due to their large mass and small aspect ratio, icebergs pose a threat to boats and offshore structures. Small icebergs and bergy bits can cause harm to platform hulls and are more difficult to discover remotely. When there is a risk of collision between icebergs and platforms, it is necessary to deflect its drifting course to ensure safe human operations in polar offshore regions. In this talk, I will present iceberg towing experiments carried out on Svalbard in September 2020...

This talk is part of the Mechanics Lunch Seminar series. That means 20min talks plus discussion in an informal setting.

Zoom: To obtain the Zoom meeting details please contact Timo Koch (timokoch at math.uio.no).

Abstract: We report on the observation of gravity-capillary wave turbulence on the surface of a fluid in a high-gravity environment. By using a large-diameter centrifuge, the effective gravity acceleration is tuned up to 20 times Earth’s gravity. The transition frequency between the gravity and capillary regimes is thus increased up to one decade as predicted theoretically. A frequency power-law wave spectrum is observed in each regime and is found to be independent of the gravity level and of the wave steepness. While the timescale separation required by weak turbulence is well verified experimentally regardless of the gravity level, the nonlinear and dissipation timescales are found to be independent of the scale, as a result of the finite size effects of the system (large-scale container modes) that are not taken currently into account theoretically.

This talk is part of the Mechanics Lunch Seminar series. That means 20min talks plus discussion in an informal setting.

Zoom: To obtain the Zoom meeting details please contact Timo Koch (timokoch at math.uio.no).

Doctoral candidate Thomas Zengaffinen-Morris at the Department of Mathematics, Faculty of Mathematics and Natural Sciences, is  defending the thesis Influence of Submarine Landslide Failure and Flow on Tsunami Genesis for the degree of Philosophiae Doctor.

Abstract: I will present a Biot-Stokes formulation created by Ricardo Ruiz-Baier. The formulations consists of a fluid-structure interaction model for flow of a Newtonian fluid, coupled with Biot consolidation equations through an interface, and incorporates total pressure as an unknown in the poroelastic region. I will also present a preconditioner for this system which is robust in all parameters and apply the model to a third circulation process to show the velocity fields in the brains subarachnoid space.

This talk is part of the Mechanics Lunch Seminar series. That means 20min talks plus discussion in an informal setting.

Zoom: To obtain the Zoom meeting details please contact Timo Koch (timokoch at math.uio.no).

C*-algebra seminar talk by Bram Mesland (Leiden)

Doctoral candidate Christopher Friedemann at the Department of Mathematics, Faculty of Mathematics and Natural Sciences, is  defending the thesis Simulations of two-phase gas-liquid flow in concentric and eccentric annuli at 0 to 90 degrees inclination using the volume of fluid method for the degree of Philosophiae Doctor.

C*-algebra seminar talk by Karen Strung (Prague)

Abstract: If a droplet smaller than the capillary length is placed on a substrate with a conical shape, it spreads by itself in the direction of growing fibre radius. We describe this capillary spreading dynamics by developing a lubrication flow approximation on a cone and by using the perturbation method of matched asymptotic expansions. The droplet velocity is found to increase with the cone angle but decrease with the cone radius. We show that a film is formed at the receding part of the droplet, much like the classical Landau–Levich–Derjaguin film. By using the approach of matching asymptotic profiles in the film region and the quasi-static droplet, we obtain the same film thickness as the results from the lubrication approach. Our results show that manipulating the droplet size, the cone angle and the slip length provides different schemes for guiding droplet motion and coating the substrate with a film.​

This talk is part of the Mechanics Lunch Seminar series. That means 20min talks plus discussion in an informal setting.

Zoom: To obtain the Zoom meeting details please contact Timo Koch (timokoch at math.uio.no).

C*-algebra seminar talk by Amine Marrakchi (Lyon)

C*-algebra seminar talk by Yoshimichi Ueda (Nagoya)

Doctoral candidate Martin Tveten at the Department of Mathematics, Faculty of Mathematics and Natural Sciences, is  defending the thesis Scalable change and anomaly detection in cross-correlated data for the degree of Philosophiae Doctor.

Doctoral candidate Alice Petronella Hedenlund at the Department of Mathematics, Faculty of Mathematics and Natural Sciences, is  defending the thesis Multiplicative Tate Spectral Sequences for the degree of Philosophiae Doctor.

C*-algebra seminar talk by Olof Giselsson

Abstract: Physics-informed neural networks (PINNs) are a new and promising methodology to combine deep learning with partial differential equations (PDE). PINNs extend deep neural networks by regularizing their output to fulfill any given PDE, allowing to solve both forward and inverse PDE problems utilizing high-performance machine learning libraries such as Tensorflow and PyTorch. This talk will give a short introduction to PINNs and provide a detailed, tutorial-style code demonstration on their implementation in PyTorch.

This talk is part of the Mechanics Lunch Seminar series. That means 20min talks plus discussion in an informal setting.

Zoom: To obtain the Zoom meeting details please contact Timo Koch (timokoch at math.uio.no).

C*-algebra seminar talk by Siegfried Echterhoff (Muenster)

This is a two days online workshop with interdisciplinary attitude. It is held on 10-11 December 2020.