Vortex Shedding Optical Flowmeter based on Photonic Crystal Fiber

Area of Science:

• Optical Sensing
• Fluid Dynamics
• Fiber Optics

Background:

• Accurate measurement of low fluid flow velocities is crucial for industrial process control.
• Traditional vortex flowmeters often lack sensitivity at low flow rates.
• Photonic crystal fibers (PCFs) offer unique properties for developing novel sensing devices.

Purpose of the Study:

• To develop and characterize a PCF-based modal interferometer for enhanced low flow velocity sensing.
• To improve the sensitivity and robustness of vortex flowmeters for industrial applications.
• To investigate the sensor's performance in detecting vortex shedding frequencies.

Main Methods:

• A PCF-based modal interferometer with a protective metal casing was designed and fabricated.
• Sensor characterization was performed using a piezo actuator to assess frequency response (0-500 Hz).
• Experiments involved deploying the sensor in a vortex flowmeter setup to measure vortex shedding frequencies behind a bluff body.

Main Results:

• The developed sensor exhibited a reasonably flat response across the tested frequency range.
• The PCF sensor significantly improved the low flow rate sensitivity of the vortex flowmeter.
• A minimum detectable Reynolds number of Re = 5000 was achieved, with a linear correlation between vortex frequency and flow velocity.

Conclusions:

• The PCF-based modal interferometer with metal encapsulation provides a robust, economical, and highly sensitive solution for low flow velocity measurement.
• This technology enhances vortex flowmeter performance, making it suitable for demanding industrial environments.
• The sensor's ability to detect low flow rates opens new possibilities for process optimization and control.