A numerical study has been undertaken of the influence of a compliant boundary on absoluteinstability. In a certain parameter range absolute instability occurs in the boundary layeron a rotating disc, thereby instigating rapid transition to turbulence. The conventional useof wall compliance as a laminar-flow control technique has been to lower growth rates ofconvective instabilities. This has the effect of reducing amplification of disturbances asthey propagate downstream. For absolute instability, however, only the suppression of itsonset would be a significant gain. This paper addresses the question of whether passive wallcompliance can be advantageous when absolute instability exists in a boundary layer.

A theoretical model of a single-layer viscoelastic compliant wall was used in conjunctionwith the sixth-order system of differential equations which govern the stability of theboundary-layer flow over a rotating disc. The absolute/convective nature of the flow wasascertained by using a spatio-temporal analysis. Pinch-point singularities of the dispersionrelation and a point of zero group velocity identify the presence of absolute instability.It was found that only a low level of wall compliance was enough to delay the appearance ofabsolute instability to higher Reynolds numbers. Beyond a critical level of wall complianceresults suggest that complete suppression of absolute instability is possible. This wouldthen remove a major route to transition in the rotating-disc boundary layer.