Experimental Stand for Very-Low-Velocity Gas Flow Generation

Abstract

This article presents an experimental stand for the generation of gas flows with very low velocities. The constant volume air flow was generated in the measurement area with the use of a Mariotte bottle and a water piston (water column in a tank). The air-flow velocity was determined from the change in the height of the water piston with time, which was measured via the difference between the pressure above the water surface and the pressure at the bottom of the water column. The tests were carried out in the mean velocity range of 0.35–66 cm/s. The five different velocities of air flowing out of the measurement pipe, measured with the particle image velocimetry method were compared with the results from the water piston method. The differences did not exceed 7%.

Semi-Empirical Approach to Gas Flow Velocity Measurement by Means of the Thermal Time-of-Flight Method—Further Investigation

“…For the inflow velocity (v∞) range 0.00 ÷ 0.25 m/s, its measurement uncertainties varied from 10 to 3% of the measured values, respectively [41]. For the remaining range (up to 2.5 m/s) measurement, uncertainty was equal to 1.5% of the measured value but not less than 0.02 m/s.…”

“…A series of measurements, primarily for the velocity range below the diffusion velocity, was carried out on the second measurement stand-a specially designed measurement setup for generating the lowest flow velocities, based on a water piston driven by a Mariotte cylinder [41]. This measurement setup, after a modification that involved increasing the cross-section of the outlet pipe, allows one to obtain flow velocities from 0.01 to 0.20 m/s, with the stability from 5 to 2% and uncertainty of velocity determination from 10 to 3%, respectively.…”

“…For comparative purposes, one series of measurements carried out using probes H2 and H3 in similar measurement conditions and one series of measurements using probe H1 inclined by an angle of α = 7 • in the direction of the inflow were carried out. Additionally, in order to supplement the results obtained in the TANPOZ wind tunnel with the lowest flow velocity range, a series of measurements with the H1 probe on the water piston stand was also performed [41].…”