Point-velocity methods for flow-rate measurements in asymmetric pipe flow

Laser Doppler velocimetry (LDV) is characterized by its ability to determine local fluid velocities with high accuracy. Therefore, LDV may also be used for precise flow-rate measurements of turbulent flow in circular ducts. The uncertainty of the measurement depends mainly on the asymmetry of the axial velocity distribution and on the point-velocity method chosen to estimate the flow-rate. LDV-measurements in conjunction with velocity-area methods have been performed under different asymmetric flow conditions yielding errors in the range of one per cent. The experimental data have been transformed into analytical flow profiles, in order to investigate combinations of single-point measurements. As a result, a new multi-point method with variable centre-point factor is introduced, that reduces both the effort and uncertainty in the measurement.