Original author: Ian Smith, By Iansmith6 – Own work, CC BY 3.0
URL link: https://commons.wikimedia.org/w/index.php?curid=7469155
This flow visualization shown uses color schlieren photography to highlight the hot air rising from the tip of a soldering iron. Schlieren photography is able to visualize flow in a transparent material by analyzing the a gradient of refracted light between the high/low pressure zones surrounding the flow. I think this image is especially appealing because of how it visually conveys the flow and heat distribution of something we are all familiar with.