Piezoelectric tiles for passive flow rate monitoring across a surface

Abstract

We introduce a method for measuring the velocity of turbulent fluid flow passing through a pipe using piezoelectric tiles without penetrating the pipe, and without having previously designed the pipe to easily allow monitoring. To measure the flow, the vibrations induced on the pipe by the fluctuating pressure loading induced by the turbulent flow are measured and compared across flow speeds to establish effective invertible relationships from vibration to velocity. Measurements are reported for instrumented pipes transporting, in separate experiments, water and air. The water experiment was able to resolve linear velocity differences on the order of 1~cm/second, while the air experiment was able to resolve on the order of 15~cm/sec. Turned inside out, a similar system might be used to assess external flow velocity, determine differential velocities on opposite sides of a body traveling through air and water, and thus provide navigational data in the form of speed and attitude/angle of attack information. Although this approach is prototyped for a single sensor, it is likely to benefit substantially from the noise suppression possible when employing an array of sensors.

Figures (8)

• Figure 1: (Left) The air tube setup. (Right) The water tube setup.
• Figure 2: Processed measured vibration power for individual trials at each pump setting.
• Figure 3: The vibration response of the tube is measured for ascending and descending pump settings.
• Figure 4: Time series for the electrical signals and vibration signals associated with an outlier.
• Figure 5: After applying EMI filtering and the skewness-based outlier rejection techniques, the variability in the samples associated with each pump setting (standard deviation are shown) is modest, and allows inversion with a high degree of confidence.