In wind tunnel test, tripping wires or a local surface roughness are often applied to fixing the boundary layer transition on airfoils or wings.

在翼型或机翼的风洞试验中，常用绊线或局部表面粗糙度来固定边界层转捩。

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The vortex generators themselves are pins or vanes that protrude from the surface and set up microscopic eddies in the boundary layer.

ECONOMIST: The turbulent world of swimming