The linear impulse response for disturbances in an oscillatory Stokes layer

Numerical simulation results are reported for the linear evolution of disturbances in a flat oscillatory Stokes layer. A spatially localised form of impulsive forcing is applied. The subsequent disturbance development displays an intriguing family tree-like structure, which involves the birth of successive generations of wavepackets. The complexity of this response is likely to lead to some difficulties in the interpretation of data obtained from physical experiments. It is also noted that important features of the wavepacket behaviour can be accounted for using linear stability results based upon Floquet theory.