e-Science

Simulation tools in fluid dynamics

Introduction

The “e-science in fluid mechanics” research area has a different character compared to other research areas in FLOW. It is not focused on a single discipline of fluid mechanics but its activities span over all other research areas in FLOW. It also acts as a link to the Swedish e-Science Research Centre (SeRC) since it represents the FLOW community in that centre.

During the last 30 years, the field has experienced a change by the introduction of the computer: Numerical simulations of initially laminar, but also turbulent flows have dramatically increased our knowledge. Turbulence models of various complexity and accuracy have been developed over the years, with profound impact into the daily engineering workflow. The simulation of fluid flows usually requires a large amount of degrees of freedom. For instance, when considering turbulent flow, the range of excited scales is very wide, ranging from integral scales (of the size of the considered domain, such as an airplane wing or even a typical atmospheric eddy) down to small viscous scales on the order of a few micrometers. Thus, CFD applications have always been among the best customers of computer centres. Nowadays, DNS using up to order 10 billion grid points are feasible, and a few million grid points are considered to be small simulations.

Visualisation of the vortical structures in a jet in crossflow, showing the appearance of hairpin vortices downstream of the nozzle. Volume rendering of the 2 field. For complete animation see http://arxiv.org/abs/1010.3766.

However, the growing capability of computer systems also causes an increasing dependency of researchers on the employed simulation methodology, as the whole process chain of tools is getting more and more complex; up to the point that a complete oversight of the process is impractical for an individual scientist. Issues such as pre-processing (grid generation, initial data), simulation runs (high-performance computing on parallel systems) and post-processing (data storage, mining and visualisation), have become specialised areas of expertise, which are hardly managed by a single researcher. Rather, the processes leading up to performing a successful simulation of a problem at hand have to be considered aspects of e-Science, involving knowledge of a broad range of areas including physics, numerical analysis, computer science, and software skills. It is the aim of this research area to improve the e-Science capabilities for researchers within FLOW.

Research overview

Research environment

Within FLOW, research in computational fluid dynamics is performed in groups at KTH Mechanics, KTH Numerical Analysis, KTH Aeronautical and Vehicle Engineering.However, within the Swedish e-Science Research Centre (SeRC), also related departments with similar research interest are included, namely NORDITA, Stockholm University (Bert Bolin Centre) and LiU Management & Engineering/Mathematics. These groups are very diverse in terms of the applied computational methods and the physical problems addressed. Also, their involvement in the areas of e-Science is different: Some groups focus on code development and the related software-engineering aspects, whereas other groups mainly apply commercial codes and direct their research activities towards a deeper understanding of complex physical phenomena. The strength of the present research area directly lies in the variety of backgrounds of the members, uniquely combining strong expertise in areas such as large-scale computations, advanced numerical methods, modelling of complex flows and innovative visualisation. Members act as main developers in many of the below software projects (e.g. Simson, FEMLEGO), or as active contributors to international software projects (FEniCS, Nek5000). The wider SeRC community can also act as a meeting place for developers, sharing ideas and techniques for software development and maintenance, and support a common platform including a forum and documentation for the software packages.

The research focus lies on method development, high-performance computing (HPC), Postprocessing and coordination of e-Science activities within the FLOW Centre.

Research groups

Group of Anna-Karin Tornberg
Group of Luca Brandt
Group of Dan Henningson
Group of Philipp Schlatter

Facilities

Access to supercomputer resources via SNIC
Several codes, both for model development, validation and large-scale computations
Hosting of research data base

Collaborating organisations

PDC Centre at KTH, SeRC/SESSI, KTH Viz, Argonne National Laboratory, University of Illinois Urbana-Champaign

Key publications

Lenaers, P., Schlatter, P., Brethouwer, G., & Johansson, A. V. (2014). A new high-order method for the simulation of incompressible wall-bounded turbulent flows. Journal of Computational Physics, 272, 108-126.

Otero, E., Vinuesa, R., Marin, O., Laure, E., & Schlatter, P. (2018). Lossy data compression effects on wall-bounded turbulence: bounds on data reduction. Flow, Turbulence and Combustion, 1-23.

Schlatter, P., & Örlü, R. (2010). Assessment of direct numerical simulation data of turbulent boundary layers. Journal of Fluid Mechanics, 659, 116-126.

Offermans, N., Marin, O., Schanen, M., Gong, J., Fischer, P., Schlatter, P., Obabko, A., Peplinski, A., Hutchinson, M. and Merzari, E., 2016, April. On the strong scaling of the spectral element solver Nek5000 on petascale systems. In Proceedings of the Exascale Applications and Software Conference 2016 (p. 5). ACM.