Wind tunnel draws international team

An international collaboration has brought researchers from the University of Minnesota and the University of Melbourne to the Subsonic Aerospace Wind Tunnel at NMSU to study turbulence in an experiment notable for its scale.

The researchers are measuring wallbounded turbulence, the turbulence on the surface of tunnels. The floor of the wind tunnel was covered in Braille paper to mimic “random roughness,” creating a rough surface on the walls of the tunnel so that the effect on turbulence can be measured and studied. Rough wall turbulence is the same kind of turbulence as exists around a ship or a plane.

“All forms of transport have a turbulent boundary layer on the surface,” said Jason Monty, a postdoctoral researcher from the University of Melbourne. “The problem with it is that nobody understands turbulence.”

A better understanding of rough wall turbulence could lead to more efficient travel for ships and airplanes. For instance, ships on long voyages are significantly slowed by barnacles attaching and increasing the roughness of the surface, creating resistance.

“The problem is that the boundary layer is responsible for all the drag or air resistance on a body. You need to understand it to control drag and resistance,” Monty said. The NMSU wind tunnel is ideal for this sort of experiment, as its long flat surface is similar to a ship hull, Monty said.

A traverse, an aerodynamically shaped metal bar that stretches across the wind tunnel and holds the sensors, takes measurements as it slowly moves up and down during wind tunnel operation. The traverse is entirely computer-controlled and is capable of movements as small as one micron. The tiny five-micron flow sensors can detect the smallest changes in turbulence.