Numerical simulations of cooling air flow in electric generators, transients in hydraulic turbines, turbulence in tidal power flow, and FSI in stent grafts

SNIC 2017/1-651


SNAC Medium

Principal Investigator:

Håkan Nilsson


Chalmers tekniska högskola

Start Date:


End Date:


Primary Classification:

20306: Fluid Mechanics and Acoustics



This project will be used in four (4) numerical simulation activities: 1: Cooling air flow in electric generators 2: Transients in hydraulic turbines 3: Turbulence in tidal power flow 4: Fluid-Structure-Interaction in stent grafts 1: The electric generator project involves highly resolved computational fluid dynamics simulations (CFD) in a complex geometry with rotor-stator-interaction and with a very large number 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 conjugate heat transfer simulations involve simulations in both solid and fluid regions, and the coupling between the regions. 2: The hydraulic turbine project studies transients between different flow conditions in hydraulic turbines. 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. 3: Novel tidar power technologies are affected by the turbulent flow, and the turbulent flow is affected by the presence of the tidal power plants. We are doing highly resolved LES simulations of the oscillating tidal flow. The Reynolds number is very large, which requires a high resolution. The flow domain must be large enough to allow the turbulence to develop correctly. The oscillating tidal flow has a very long time scale. All these features give a very high computational demand. The tidal power plant is modelled using an actuator line methodology, and we are aiming for studies of entire tidal power farms. The LES results are also used in another software, for studies of how the dynamics of the power plant is affected by the turbulence. 4: 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 recently had a period of development and testing of new methodologies and a switch between a PhD project and a post-doc, as well as a switch between two PhD projects (as well as some experimental activities). We therefore had an unexpected dip in usage during 2016 and to some extent also during 2017. During 2018 all the projects are up to speed, and in need of al the resources they can get. We have a history of using the granted resources from previous years, except for 2016.