Reproduction of air velocity in the entrance region of the pipe

N. Pedisius, A. Bertasiene

Abstract

Information about the airflow development in pipes in the entrance region is still not thoroughly investigated due to the complexity and restricted access for experiments. However, the reproduction of air velocity values, as well as calibration of the devices, is usually made in free streams from the nozzles or in the entrance region of the channels (pipes). In this study, different flow regimes have been investigated using different air velocity measurement methods for mean velocity to define. Experimental and numerical results in the entrance region of the pipe and in the test chamber of higher dimensions give a broad spectrum of information about the developing flow. Ultrasonic anemometer (UA) installed into the entrance region of the aerodynamic test facility shows reliable and highly comparable results in a wide range of velocities with another non-intrusive method – laser Doppler velocimetry (LDA). Due to the fast response, it enabled to analyse fluctuations in the flow. The mean air velocity values were determined from the singe path sound propagation time in the pipe with a defined distance between the transducers placed at an angle of 45 degrees with the main axis. Local vortices identified in the flow might have influenced the low-frequency fluctuations and the scatter of measurement results. Moreover, high-frequency fluctuations found in the flow originated from the flow turbulence and the electronic or acoustic noise. The stabilisation of the entrance region and the boundary layer of the pipe influenced mean velocity value, velocity distribution and axial velocity development in different test sections of the pipe. Along with the recirculation zones in cavities of ultrasonic transducers they are the essential impact factors on velocity value defined.

Download

IMEKO-TC9-2019-100.pdf

DOI

-

IMEKO TC

TC9 - Flow Measurement

Back to the proceedings