Quote:
Originally posted by Hawk:
Back to that image of the smoke trails around the wings Moby.....

Quote:
Showing the Airflow in a Wind Tunnel. A technique often used in wind tunnels is to introduce smoke in front of the airfoil that is being tested. The smoke comes from regularly-spaced point sources, and the wind flow in the tunnel spreads it out into parallel lines, called streamlines. The streamlines make it possible to visualize the airflow over the airfoil. When the lines continue smoothly over and past the airflow, they show that the flow remains laminar, and that the airfoil is creating very little drag. When the streamlines show more chaotic, turbulent flow, they indicate that the airfoil is creating more drag. You can do something similar with a wind tunnel by stretching thin strings across the flow path, above and below your airfoil test zone. Clip them in place so you can move them up and down to fit different airfoil shapes. Attach a ribbon (about 25 cm long) to each string. Use a stick attached to your airfoil to hold it while you place it in the flow path, between the ribbons. The ribbons will act like the smoke streamlines, so that you can visualize whether the flow over your airfoil is turbulent or laminar. Try different airfoil shapes and measure which have the most laminar and the most turbulent flow. (Parker, 2005, 18–19)
Taken from HERE

The smoke is released from a point on the wall, much in the same way that a rope is attached to a point on the wall wink
That smoke is not attached, though.
_________________________
"Nature has constituted utility to man the standard and test of virtue. Men living in different countries, under different circumstances, different habits and regimens, may have different utilities; the same act, therefore, may be useful and consequently virtuous in one country which is injurious and vicious in another differently circumstanced" - Thomas Jefferson, moral relativist