An inverse problems approach to micro-PIV for measuring flow around freely flying tiny insects

Area of Science:

• Fluid dynamics
• Insect biomechanics
• Optical measurement techniques

Background:

• Traditional brightfield micro-particle image velocimetry (micro-PIV) is limited to aqueous solutions and suffers from poor signal-to-noise ratio.
• Measuring the complex aerodynamics of freely flying insects, especially sub-millimeter species, presents significant challenges.
• Simultaneously capturing 2D flow fields and 3D kinematics of insect flight is difficult with existing methods.

Purpose of the Study:

• To introduce an advanced brightfield micro-PIV system capable of measuring 2D flows generated by freely flying sub-millimeter insects.
• To simultaneously measure the 3D wing and body kinematics of these insects during flight.
• To overcome the limitations of traditional micro-PIV in terms of medium and signal quality for insect flight studies.

Main Methods:

• Development of a novel aerosolization system for particle delivery in insect flight studies.
• Implementation of an inverse problems approach for image preprocessing to enhance particle detection.
• Optimization techniques to determine particle positions relative to the focal plane and generate synthetic, in-focus images.

Main Results:

• Demonstration of a 0.85 mm tobacco whitefly (Bemisia tabaci) generating a 0.5 m/s downward jet using a deep U-shaped wingtip trajectory during wing clap.
• Successful measurement of 2D flow fields around a flying insect.
• Simultaneous capture of 3D wing and body kinematics.

Conclusions:

• The novel brightfield micro-PIV technique effectively measures insect flight aerodynamics, overcoming previous limitations.
• This method provides a valuable tool for validating numerical simulations of tiny insect flight.
• The technique is adaptable for studying the aerodynamics of diverse insect species with varying morphologies.