A theoretical study into the effects of wall compliance on the stability of therotating-disc boundary layer is described. A single-layer viscoelastic wall model is coupledto a sixth-order system of fluid stability equations which take into account the effects ofviscosity, Coriolis acceleration, and streamline curvature. The coupled system of equationsis integrated numerically by a spectral Chebyshev-tau technique.

Travelling and stationary modes are studied and wall compliance is found to greatlyincrease the complexity of the eigenmode spectrum. It is effective in stabilizing theinviscid Type I (or cross-flow) instability. The effect on the viscous (Type II) eigenmodeis more complex and can be strongly destabilizing. An analysis of the energy flux indicatesthat this destabilization arises as a result of a large degree of energy production byviscous stresses at the wall/flow interface.

The Type I and II instabilities are shown to be negative and positive energy wavesrespectively. The co-existence of eigenmodes of opposite energy type indicates thepossibility of modal interaction and coalescence. It is found that, compared with the rigiddisc, wall compliance promotes the interaction and coalescence of the Type I and IIeigenmodes. There is an associated strong instability which appears to be characterized bymarked horizontal motion of the compliant surface. Modal coalescence is interpretedphysically as producing local algebraic growth which could advance the onset of nonlineareffects.