Flow visualization speaks to me when it is involved with trains in any way. I particularly enjoy this photo of Rio Grande Southern 20 at the Colorado Railroad. In this picture, the locomotive is emitting condensation from anywhere that it possibly can. The cylinders blow out condensate to reduce the risk of blowing a cylinder head. The blast pipes draft smoke out from the fire and up the smoke stack. The safety valve lifts, creating an ear-piercing hiss, but reassuring us that the locomotive is working properly. All of these releases of various forms of water vapor are visually amplified by the sub-zero temperature during which the photo was taken. Water condenses faster in colder temperatures, so much of what would be invisible steam is now clear for us to see. The various ejections of condensate make the locomotive feel alive and powerful. Steam locomotives exhibit my favorite form of flow visualization in this way.
Credit: Erik C. Lindgren, Click the photo to view the original post on Flickr
