Numerical simulations of cooling air flow in electric generators, FSI in stent grafts, and transients in Francis turbines

Dnr:

SNIC 2016/1-563

Type:

SNAC Medium

Principal Investigator:

Håkan Nilsson

Affiliation:

Chalmers tekniska högskola

Start Date:

2017-01-01

End Date:

2018-01-01

Primary Classification:

20306: Strömningsmekanik och akustik

Webpage:

http://www.chalmers.se/sv/personal/Sidor/hakan-nilsson.aspx

Allocation

Abstract

This project will be used in three activities: 1: Cooling air flow in electric generators 2: Fluid-Structure-Interaction in stent grafts 3: Transients in Francis turbines 1: The electric generator project involves highly resolved computational fluid dynamics simulations (CFD) in a complex geometry with rotor-stator-interaction and with lots of boundary layers that need to be resolved with low-Reynolds number meshes. That requires excessive computational meshes, and thus a substantial amount of computational resources. The activity is in its final state before the dissertation of a PhD, and the project will secure the possibility for the PhD student to do the final required simulations. The simulations done so far in the project have been done at Triolith, and we need to do the final simulations at Triolith as well. We also need to take care of data that has already been produced before. After finalizing this PhD project there is a new PhD project continuing in the same field, going towards conjugate heat transfer simulations. 2: Stent grafts are used to treat abdominal aortic aneurysms. We are studying the forces acting on stent grafts under realistic conditions, aiming at modifications of the stent grafts that reduce mortality. The stent graft project involves Fluid-Structure-Interaction simulations, i.e. simulations that couple the solution in the fluid domain with the deformation of the solid domain. Such simulations are much more demanding than each individual simulation, since a strong coupling needs an iterative procedure where the fluid and solid domains are computed a number of times each time step. The strong coupling is needed due to the properties of the case: large deformations and similar densities in the solid and fluid domains. We also need to investigate a large number of cases for a parameter study. Each case will be run in parallel, and the cases will be run in parallel. 3: The Francis turbine project studies transients between different flow conditions in a Francis turbine. This requires a detailed resolution of the flow details, using rotor-stator-interaction, adjustable blade angles, and advanced turbulence modeling. Very long time scales need to be included, related to those of the transient processes. Therefore there is a need for a substantial amount of computational resources. The history of our usage for 2016 shows that we did not use the resources we were granted, and we should have asked for a reduction of the resources. The main thing that happened was that an extremely resource-demanding PhD project ended before summer. It should have been followed up by a similar post-doc-project, which it did, but problems in that project caused our usage to drop completely. My hope was that it would pick up again, but it didn't. At the same time there was as well a focus on experimental activities in the electric generator project. Also the other projects listed in that application finished. We have a history of using the granted resources from previous years.