Assessment of event-based vision sensor cameras for measuring bubbly flow characteristics

Area of Science:

• Fluid Dynamics
• Optical Measurement Techniques
• Flow Visualization

Background:

• Characterizing bubble dynamics in multiphase flows is crucial for various industrial processes.
• Conventional high-speed (HS) cameras face limitations in data rates and temporal resolution for dense bubbly flows.
• Event-based vision sensor (EVS) cameras offer a novel approach with high temporal resolution and low data rates.

Purpose of the Study:

• To assess the capability of EVS cameras for measuring bubble motion, size, and shape in complex bubbly flows.
• To benchmark EVS camera performance against conventional HS cameras.
• To identify advantages and limitations of EVS cameras in bubbly flow analysis.

Main Methods:

• Benchmark evaluation using precisely manufactured particles in quiescent water, synchronized with an HS camera.
• Characterization of bubbles generated by compressed air injection at various pressures.
• Implementation of pulsed illumination to address EVS camera event saturation in dense bubbly flows.

Main Results:

• EVS cameras demonstrated high accuracy in measuring particle velocity ( < 0.65% difference) and diameter ( < 2.4% difference) compared to HS cameras.
• Comparable performance to HS cameras for bubble size and velocity at low to moderate injection pressures.
• EVS cameras successfully captured dense bubbly flows with pulsed illumination, overcoming event saturation issues.

Conclusions:

• EVS cameras provide accurate measurements of bubble motion and dimensions, comparable to HS cameras.
• EVS cameras offer unique advantages, including direct bubble velocimetry from recorded tracks and high-speed real-time imaging.
• EVS cameras are a promising tool for advanced bubbly flow characterization, especially in challenging conditions.