The comparison of air flow LDA measurement in simple cylindrical and cylindrical tube with flat external wall

Abstract

The application of 2D laser Doppler anemometry systems is considered, in the case of fluid flow confined in simple cylindrical and in cylindrical tube with flat external surface of the wall. Geometric optics laws are applied to the central lines of laser beams. Measurement volume dislocations, calibration angles and distances of measurement volume centre from the photo-detector field of view centre are expressed. The expressions derived in this paper were applied to specific turbulent swirl flow in pipe. That revealed several advantages of use of a simple cylindrical tube over nowadays favored use of cylindrical tube with flat external surface. Those results suggest that current avoiding of laser Doppler anemometry measurements with simple cylindrical tubes should be reconsidered.

Keywords

• laser doppler anemometry
• snell's law
• measurement volume dislocation
• decalibration