Deutsches Zentrum f. Luft- und Raumfahrt e.V. (DLR)

Kolloquium am 02.10.15

REFERENT: Prof. Peter J. Thomas
Fluid Dynamics Research Centre, School of Engineering,
University of Warwick
(Eingeladen von Prof. Dillmann, AS-LTG Gö)
TITEL: Effects of Surface Roughness on the Stability of the Rotating-Disk Boundary Layer
ZEIT: FREITAG, 02.10.2015
11:30 Uhr Vortragsbeginn
ORT: DLR Göttingen, Adolf-Busemann-Raum (Hörsaal Haus 7, EG)
The classic belief that surface roughness inevitably increases the skin-friction drag that acts on bodies moving through a fluid has been superseded. The right sort of roughness can reduce drag. The challenge that remains is to exploit this fundamental insight in practice for the development of new drag-reduction techniques.
I will present results of our theoretical study investigating the effects of surface roughness on the stability of the boundary-layer flow over a rotating disk. This flow represents a generic example of a general class of boundary layers that share the common characteristic of a cross-flow velocity component. Boundary layers of this type exist on highly-swept wings of aircraft. All such boundary layers display similar laminar-turbulent transition characteristics. Our results reveal stabilising, that is energetically beneficial, effects on the dominant instability mode responsible for transition in these boundary layers. Our aim is to develop theoretical methods to enable the design of energetically optimal surface roughness, for laminar flow control, in the context of new, passive drag-reduction techniques for boundary layers with a cross-flow component.