Image shifting technique to resolve directional ambiguity in double-pulsed velocity

Area of Science:

• Fluid dynamics
• Optical measurement techniques
• Laser velocimetry

Background:

• Pulsed laser velocimetry is crucial for measuring fluid flow.
• Determining velocity direction can be challenging with conventional methods.
• Existing techniques may be sensitive to particle scattering and illumination variations.

Purpose of the Study:

• To introduce and validate image shifting as a robust method for pulsed laser velocimetry.
• To demonstrate the independence of image shifting from scattering properties and illumination intensity.
• To assess the performance limits of image shifting for velocity measurement.

Main Methods:

• Implementing image shifting in pulsed laser velocimeter systems.
• Utilizing rotating mirror systems for lower velocity ranges.
• Employing electro-optic systems for higher velocity measurements.

Main Results:

• Image shifting successfully determines displacement direction and velocity for all pulsed laser velocimeter types.
• The method shows independence from particle scattering and illumination intensity differences.
• Negative velocities up to 10 m/s were offset with rotating mirrors.
• Velocities up to 500 m/s are estimated to be measurable with electro-optic systems.

Conclusions:

• Image shifting offers a high-performance, versatile solution for pulsed laser velocimetry.
• This technique overcomes limitations of scattering and illumination sensitivity.
• Image shifting significantly expands the measurable velocity range, particularly for negative velocities.