Illustration of a highly compressive flow leading to both cork-free voids and regions with unnecessarily high cork density. Left panel: initial homogeneous cork placement in a 2D simulation, with one cork per grid cell. The top of the convection zone is located roughly at z = 0 Mm. Right panel: same simulation, but now after 300 s of solar time. The bottom and left axes are in computational pixels, the upper and right axes show physical size. The panels only show a subfield of the full simulation which had 512 × 496 grid cells. Corks have been swept up in convective downflows and shock fronts, and large cork-free regions appear above z = 1 Mm.