An All-Optical System for Transit Time Estimation in Fluids Using Single Source and Detector

The estimation of vortex convection velocity and frequency of vortices is a challenging task that requires sophisticated experimental and computational techniques. Several methods have been developed to measure the velocity of vortices, including vortex flowmeters (vortex shedding flowmeter and Karman vortex flowmeter), pressure-sensitive paints (PSPs), and magnetic resonance velocimetry (MRV). These methods have different strengths and weaknesses, and the choice of technique depends on the specific application and the level of accuracy required. In this article, a photonic crystal fiber (PCF)-based dual-sensor optical flowmeter (vortex shedding flowmeter) is proposed and demonstrated for vortex detection and convection velocity estimation, allowing for the detection of a broad range of Reynolds numbers at a reasonable cost. The autocorrelation technique is demonstrated for estimating integral time scale (ITS) and convection velocity from the combined signal of two sensors using a single source and a detector. The proposed scheme eliminates the requirement of multiple sources and detectors for two or more sensor-based systems. Results show a significant improvement in signal-to-noise ratio (SNR) even at a low flow rate of 0.29 m/s.