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Rotating disks and cones - a legacy of von Kármán

Time: Thu 2023-02-23 10.30 - 11.30

Location: Faxén, Teknikringen 8

Participating: Henrik Alfredsson

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In a seminal paper from 1921 by von Kármán, boundary layers in general were discussed and in two of the nine sections results for the boundary layer over a rotating disk were presented. In the coming years the research community was mainly interested in using the rotating disk as a tool to determine boundary-layer friction. A disruptive paper by Gregory et al. in 1955 showed through flow visualization the existence of stationary crossflow vortices on the disk prior to transition to turbulence. Forty years later in 1995, Lingwood made another disruptive discovery, showing an absolute instability in the laminar boundary layer on the disk, the first absolute instability of any boundary-layer flow to be found. After those discoveries most research aimed to further investigating the instabilities occurring on the disk that ultimately lead to transition. Today the understanding is that there exist two alternative routes to transition, a ‘convective route’ and an ‘absolute route’, both relying on a secondary absolute instability before transition. The rotating disk can be seen as a special case of the general set of rotating cones and recent research has shown that broad cones behave in a similar way as the disk whereas sharp cones are susceptible to a different type of instability. In the seminar some aspects of our experimental and numerical work will be presented.

The research presented in the seminar has been carried out in collaboration with
R.J. Lingwood, S. Imayama, E. Appelquist, P. Schlatter, T. Kawata, K. Kato and
A. Segalini and has mainly been supported by the Swedish Research Council (ASTRID and SERAFINA projects), but also from FLOW, Carl Trygger Stiftelse, JSPS and KTH.


Additional reading:

Park, M., Leahey, E. & Funk, R.J. Papers and patents are becoming less disruptive over time. Nature 613, 138–144 (2023). doi.org/10.1038/s41586-022-05543-x

Page responsible:Ardeshir Hanifi
Belongs to: FLOW
Last changed: Feb 21, 2023