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ME 563 - Intermediate Fluid Dynamics - Su Lecture 0 - Visual fluids examples Fluid dynamics is a unique subject because it’s very visual. The book “An Album of Fluid Motion” by Milton van Dyke (on reserve at Wendt) is a collection of fascinating images from fluids experiments. You really can’t say you understand fluids if you only think of it in terms of equations. Figure 1 is a top view of a triangular wing immersed in a flow of water (moving from left to right in the image). Colored fluid, appearing as white, is introduced near the leading edge. The wing Figure 1: Turbulent transition in flow over a wing. is inclined at a 20◦ angle of attack. Initially the fluid pattern is very smooth, then the filaments of colored fluid make a very abrupt transition to turbulence. The abruptness of the turbulent transition is interesting for many reasons, not least of which is that it’s not really predicted by the equations of fluid flow. Another interesting property of fluid flows is that the organization of it is very persistent. The upper left photo in Fig. 2 is of the wake of a circular cylinder in a water flow. The cylinder is at the left edge of the photo. The mean flow is very slow – about one cylinder diameter per second. The Reynolds number is 105. The alternating pattern of eddies (vortices) is called the ‘K`arm` an vortex street.’ Intuitively, it kind of makes sense that a slow, laminar flow would be very organized. The upper right photo in Fig. 2, showing the wake of a plate at a 45◦ angle of attack, is taken at a flow that is, relatively, about 40 times faster (Reynolds number 4300). The flow in this case is turbulent, but even so, the alternating pattern of eddies is visible above the randomness. To drive home this point further, the lower photo in the figure is of the wake of a tanker inclined at roughly 45◦ to the mean current. The pattern assumed by the oil slick is amazingly similar t