Evidence for transient disturbance growth in a 1961 pipe-flow experiment

Abstract

Evidence is presented for what appears to have been nonmodal disturbance growth in a pipe-flow experiment performed by Kaskel [Technical Report No. 32-138, Jet Propulsion Laboratory, California Institute of Technology, 1961], based on a comparison of the experimental traces of disturbance amplitude with predictions of transient amplitude growth calculated from the underlying linear stability operator. Owing to the geometry of the experimental disturbance generator, modes having azimuthal wavenumbers n=0, 6 and 12 are expected to contribute the bulk of the disturbance energy, and numerically predicted amplitude growth versus downstream distance is in good agreement with the experiment.