Benard cells - parallel roll structures - inside a flat enclosure containing air. Result of a numerical simulation using the <a href="https://en.wikipedia.org/wiki/Computational_fluid_dynamics" class="extiw" title="en:Computational fluid dynamics">CFD</a> software Flotherm. The enclosure dimensions were set to 100 x 100 x 15 mm<sup>3</sup>, the temperature difference between the upper and the lower plate was set to 1 °C. The air speed distribution is shown at a cross-section in the middle between the upper and the lower enclosure walls. The maximum speed is approximately 0.3 mm/s.
<a href="//commons.wikimedia.org/wiki/User:Harke" title="User:Harke">Harke</a>
<span class="int-own-work" lang="en">Own work</span>