Development of Impulsively Excited, Linearized Poiseuille Flow

We simulate the equations of linearized (around Poiseuille flow) 3D channel flow with body force fields as inputs. With zero initial conditions, introduce a body force which is a spatio-temporal impulse near the bottom wall. Physically, this can be thought of as a concentrated momentary “detonation” near the bottom wall. The pictures below show the development of stream-wise vorticity and velocity thereafter. Note the striking resemblance to some features of so-called “turbulnet spots” (e.g. the arrow head shape, span-wise spreading, and alternating stream-wise streaks and vortices). Keep in mind that these are the linearized Navier-Stokes equations!