Laser optical flow measurement
Requirements of EN 1434 – fully developed velocity profiles
EN 1434-4:2015 contains requirements about the velocity characteristics of test benches for calibration of flow sensors. According to part 4, chapter 7.22 the calibration test benches for flow sensors must contain fully developed and undisturbed velocity profiles. The minimum criteria are stated in annex C. For the validation and conformity the “Guidelines for the Fluid Mechanical Validation of Calibration Test-Benches in the Framework of EN 1434” can be used.
For validation of the mentioned test benches we use the Laser Doppler Velocimetry, which is a contactless measuring technique to acquire local velocities of the flow. For the optical access to the fluid, a special window chamber will be mounted. The inside diameter of this chamber is kept the same as the pipe diameter of the test bench. Thereby possible impacts to the velocity profile will be prevented.
After installation of the measurement equipment, the local velocities at the prescribed flow rates will be measured along a special measuring grid. For the assessment of the pipe velocity, the results are compared to standard laminar and turbulent profiles and used to determine the performance of the test-bench by calculating the relevant flow coefficients. Details to the whole process are contained in “Guidelines for the Fluid Mechanical Validation of Calibration Test-Benches in the Framework of EN 1434” written by “Task Force laser optical flow diagnostics”.
M. Turiso, M. Straka, J. Rose, C. Bombis, D. F. Hinz (2018): The asymmetric swirl disturbance generator: Towards a realistic and reproducible standard (Link)
S. Graner, D. F. Hinz, C. Breitsamter (2016): Downstream relaxation of velocity profiles in pipe-flow with swirl disturbances (Link)