The University of Southampton
University of Southampton Institutional Repository

Direct numerical simulations of forced and unforced separation bubbles on an airfoil at incidence

Jones, L.E., Sandberg, R.D. and Sandham, N.D. (2008) Direct numerical simulations of forced and unforced separation bubbles on an airfoil at incidence Journal of Fluid Mechanics, 602, pp. 175-207. (doi:10.1017/S0022112008000864).

Record type: Article


Direct numerical simulations (DNS) of laminar separation bubbles on a NACA-0012 airfoil at Re-c = 5 x 10(4) and incidence 5 degrees are presented. Initially volume forcing is introduced in order to promote transition to turbulence. After obtaining sufficient data from this forced case, the explicitly added disturbances are removed and the simulation run further. With no forcing the turbulence is observed to self-sustain, with increased turbulence intensity in the reattachment region. A comparison of the forced and unforced cases shows that the forcing improves the aerodynamic performance whilst requiring little energy input. Classical linear stability analysis is performed upon the time-averaged flow field; however no absolute instability is observed that could explain the presence of self-sustaining turbulence. Finally, a series of simplified DNS are presented that illustrate a three-dimensional absolute instability of the two-dimensional vortex shedding that occurs naturally. Three-dimensional perturbations are amplified in the braid region of developing vortices, and subsequently convected upstream by local regions of reverse flow, within which the upstream velocity magnitude greatly exceeds that of the time-average. The perturbations are convected into the braid region of the next developing vortex, where they are amplified further, hence the cycle repeats with increasing amplitude. The fact that this transition process is independent of upstream disturbances has implications for modelling separation bubbles.

PDF JonesSandbergSandhamJFM2008.pdf - Accepted Manuscript
Download (2MB)

More information

Submitted date: 21 August 2007
Published date: 10 May 2008
Keywords: direct numerical simulation, airfoil, aerofoil, laminar separation bubble, transitional separation bubble
Organisations: Aerodynamics & Flight Mechanics


Local EPrints ID: 55698
ISSN: 0022-1120
PURE UUID: 12aaa3fd-6501-4d46-a17a-63ebdcc92c34

Catalogue record

Date deposited: 05 Aug 2008
Last modified: 17 Jul 2017 14:32

Export record


Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton:

ePrints Soton supports OAI 2.0 with a base URL of

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.