This paper was motivated by the possibility of extracting from a vortex-shedding strut, in addition to flow velocity V, information on fluid density ρ or temperature T, and combining them to obtain mass flowrate. Shedder shapes were diamond and bluff polygon. These shapes are compared as vortex shedders in flowing air or water. V is obtained from the shedding frequency f. In water, V ranged from 0.5 to 4 m/s and, in air, from 0.3 to 15 m/s. Clamp-on ultrasonic transducers generated and, on the diagonally opposite side of the pipe, received the beam that obliquely traversed the wake of the shedder. A continuous-wave transmission across the fluid was modulated by vortices passing through the beam. The modulation frequency yielded f. In air, the bluff polygon yielded f over a 50:1 flow range, which was better than the diamond's flow range of 20:1. Whether the shedder was a diamond or a bluff polygon, and the fluid air or water, f correlated approximately linearly with the flow velocity V. Using one path of an ultrasonic tag clamp-on flowmeter system, the measured vortex-shedding frequencies were found to be in reasonable agreement with computational-fluid-dynamic predictions for diamond and for bluff-polygon struts. Collectively, the pipe Reynolds number (Re) range was 1000-200000. With both shedders, operation was demonstrated in laminar- and turbulent-flow regimes. In water flow tests, rotating the diamond (aspect ratio = 3) through 90° about its axis, from broadside to airfoil, diminished the Strouhal number by 17%. When the diamond shedder was tested as a torsional density sensor in flowing air or water, no torsional transit time effect of V was observed, confirming for the first time a 1989 prediction. The negative result in flowing water implies that there were no attached bubbles or microbubbles.
All Science Journal Classification (ASJC) codes
- Electrical and Electronic Engineering