Experimental investigations of the location of a piezoelectric probe in a vortex flow sensor

Abstract

Three fundamental problems about the vortex flow sensor—bluff body design, signal detection method and signal processing method—have been mainly discussed by a number of researchers in recent years. However, another significant thing is that the position for vortex signal detection, the location of a piezoelectric pressure probe in a vortex flow sensor, is seldom investigated, which is the focus of this paper. It is known that the quality of vortex signals is directly related to the probe's location. Therefore, the low limit of measurement for a vortex flow sensor can be expanded by searching the optimum position for detection. Experiments were carried out in a water channel to analyze the pressure signals downstream of the bluff body. The vortex signal intensity, frequency, signal-to-noise ratio and uncertainty of the Strouhal number at each position were discussed. Finally, the optimum regions for vortex signal detection (probe location) for three bluff bodies were given: the distance between the bluff body and the position for detection is 50–75 mm when the width of the bluff body d = 14 mm, the distance is 75–125 mm when d = 22.5 mm and the distance is 75–150 mm when d = 28 mm. Meanwhile, numerical simulations on flow field were adopted to explain the experimental results.