Laminar-turbulent transition of rotating-disk flow - an experimental and numerical approach

Författare: Imayama, S.I., Appelquist, E., Lingwood, R. J., Schlatter, P., Alfredsson, P.H.
Dokumenttyp: Konferens
Tillstånd: Publicerad
Tidskrift: 10th ERCOFTAC SIG 33 Workshop, Sandhamn, Sweden, May 29-31, 2013
År: 2013


A main objective of this experimental and numerical work is to investigate laminar- turbulent transition of rotating-disk flow. The observation that transition occurs at a quite specific Reynolds number led Lingwood (1995) to suggest that the transition is due to an absolute instability. In experiments typically 28 to 32 stationary vortices are observed and appear to dominate the flow within the convectively unstable region (see e.g. Gregory et al. 1955) since such vortices are excited by minute roughnesses on the disk surface, which reinforce the disturbance pattern continuously. However Lingwood (1995) found that travelling waves made the flow absolutely unstable above R = 507 (R is Reynolds number based on the radius). The numerical simulation has the advantage that the convective stationary disturbances can be avoided and thereby enable detailed studies of the absolute instability, whereas for experimental studies it is hard to isolate the stationary disturbances from the travelling and hence the absolute instability. The figures below show developments of the stationary convectively unstable vortices by visualizing the azimuthal velocity component and there is a good agreement between experimental and numerical data. We will discuss how Lingwood’s absolute instability mechanism can be observed in our experiments and simulations of the transition process.

Abstract (page28)