LDV measurements near the step in an axisymmetric sudden expansion air flow

Radial velocity measurements using an LDV in axisymmetric sudden expansion flows have been difficult to make because of optical aberrations introduced by the curved tube wall. The present investigation utilized a specially designed correction lens to overcome this problem. This allowed both radial and axial velocity and turbulence intensity fields to be mapped out in the near-step region. The weak secondary recirculation zone (corner eddy), which is predicted theoretically and has been seen in earlier flow visualization studies, was clearly identified and mapped.