Event-based particle image velocimetry for high-speed flows

Abstract The article describes the implementation of a particle image velocimetry system based on event-based vision (EBV) capable of providing time-resolved, two-component flow field data at frame rates exceeding <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mn>2.5</mml:mn> <mml:mstyle scriptlevel="0"/> <mml:mrow> <mml:mtext>kHz</mml:mtext> </mml:mrow> </mml:mrow> </mml:math> . Compared to previous event-based imaging velocimetry (EBIV)systems the present setup is applicable to high-speed flows in the transonic regime and beyond. At the core of the measurement principle is the separation of the two laser pulses onto two imaging channels. Using orthogonally polarized pulses of light to illuminate micrometer sized particles carried with the flow, the dual-EBV camera setup incorporates a polarizing beam-splitter cube to redirect the scattered polarized light onto the respective EBV detectors. The proposed high-speed EBIV measurement approach is demonstrated on a high-speed ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mrow> <mml:mi>Ma</mml:mi> </mml:mrow> <mml:mo>=</mml:mo> <mml:mn>0.5</mml:mn> </mml:mrow> </mml:math> ) free jet with inter-pulse delays down to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mn>100</mml:mn> <mml:mstyle scriptlevel="0"/> <mml:mrow> <mml:mi>ns</mml:mi> </mml:mrow> </mml:mrow> </mml:math> . For cases in which polarization separation cannot be realized, a two-color illumination of the particles with a dichroic mirror on the camera side is proposed.