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Air Force Builds Quiet Mach 6 Wind Tunnel

Posted by ScuttleMonkey on from the hold-on-to-your-hat dept.

An anonymous reader writes "To help design 'scramjets' -- vehicles that'll travel thousands of miles per hour as they leave the atmosphere and zip around the globe -- the U.S. Air Force has just funded a wind tunnel that operates quietly at Mach 6. To get a quiet flow, the throat of the Mach 6 nozzle must be polished to a near-perfect mirror finish, eliminating roughness that would trip the flow."

3 of 153 comments (clear)

  1. "Quiet"? by timeOday · · Score: 3, Interesting
    From reading the article, I gather "quiet" is being used here as a technical term which is roughly synonymous with laminar, or lack of turbulence (rather than "gee I wish my vacuum cleaner were quiet").

    Can anybody with the right background tell me whether that's the case?

  2. Re:Some further comments by Moofie · · Score: 3, Interesting

    Columbia broke up somewhere north of Mach 12, I believe.

    I'd be much, MUCH more concerned about an engine unstart than about a mechanical problem with the heat shielding system. So much so, that I'd be totally unwilling to fly aboard a scramjet-powered aircraft that had a pilot with a joystick in his hand.

    --
    Why yes, I AM a rocket scientist!
  3. Re:Super Smooth vs. Dimples... by penguin121 · · Score: 3, Interesting

    The reason that dimples work for a golf ball is exactly the same reason they would be counter productive for the wind tunnel. Basically the dimples induce a turbulent flow around the golf ball, which reduces the flow seperation at the rear of the ball as compared to that resulting from laminar flow over a smooth ball. By reducing the size of the flow separation region, the pressure drag on the ball is significantly reduced, allowing the ball to travel farther. Now in the case of the wind tunnel turbulent flow along the walls would generate noise that would interfere with the experiments, so they want as smooth a surface as possible to minimize turbulence at the tunnel walls, thereby minimizing the background noise.