LDA Measurement in Cylindrical Containers without Using Planar Secondary Units

Abstract

To measure velocity components using the laser Doppler anemometry (LDA)in a cylindrical surface, as in a hydrocyclone, traditionally, one encloses the top circular tube of the hydrocyclone with a flat surface box to minimize the refraction effects of laser beams caused by the curved solid walls. In this brief study, an alternative procedure is suggested to reorient the laser beams to measure the mean and fluctuation velocity components. Adopting the beam orientation suggested—at a single point in the flow field—the axial and circumferential mean velocity components, along with the corresponding turbulent normal and shear stress components, can be determined. Test results confirm that the proposed method is valid to get data related to the mean velocities and the Reynolds stresses at a single point in the flow field of a hydrocyclone. The suggested procedure with slight modifications can be applied to measure velocities in the flow field formed by other circular surfaces, such as cones.