Abstract
Both vortex flowmeters and fluidic flowmeters form a family of the hydrodynamic oscillator type flowmeters, since the oscillation of wakes in vortex flowmeters and that of jets in fluidic flowmeters have geometrical and hydrodynamic complementarity, and there exist a unified model describing fluid motion in the hydrodynamic oscillator type flowmeter. Furthermore, topological isomorphism between the flow fields of both flowmeters leads to a new fluidic oscillator which consists of a jet and a bluff cylinder. The objectives of the research are to clarify the mechanism of the oscillation and to apply the oscillator to a flowmeter. The relationship between the velocity at the inlet nozzle and the oscillation frequency for the various combinations of geometric parameters were measured with the air as operating fluid. The results are summarized as follows:
1. A bluff cylinder-so called target-is indispensable to the oscillator; the less the bluffness, the higher the frequency.
2. The oscillation frequency is almost inversely proportional to the distance between the target and the nozzle.
3. A downstream contraction increases the frequency and stabilizes the oscilation; the nearer and the narrower the contraction, the higher the frequency.
4. The wider the jet, the higher the frequency.
These results together with flow visualization studies conclude that the degree of the deflection of the jet from the natural reattachment streamline mainly determines the oscillation frequency. Since the deflection depends on the position and the bluffness of the target, proposed oscillator is a hybrid of fluidic and vortex flowmeters. The experimental results also show that the oscillator shares the merits of hydrodynamic oscillator type flowmeters and is applicable to low flowrate measurement.
