Transient growth calculations obtained directly from the Orr-Sommerfeld matrices

We introduce and validate an algorithm to compute transient amplication factors for the Orr-Sommerfeld-Squire linear theory for parallel two-phase flow. We further introduce direct numerical simulation as a way of comparing the linear theory with early-stage wave growth in simulations. The simulation results are drawn from a strongly supercritical parameter case wherein the modal growth rates are strong. In this case, the modal growth dominates the transient growth