1. Stereo and time-resolved PIV for measuring pulsatile exhaust flow from a motorized engine
- Author
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Yukika Kuga, Ryo Yamamoto, Yoichi Ogata, Hideaki Yokohata, Keiya Nishida, Haruna Yanagida, Junichi Oki, and Kazuhiro Nakamura
- Subjects
Technology ,Reversed flow ,Science (General) ,Pulsatile flow ,02 engineering and technology ,01 natural sciences ,010305 fluids & plasmas ,Physics::Fluid Dynamics ,Q1-390 ,Flow separation ,proper orthogonal decomposition ,0203 mechanical engineering ,particle image velocimetry ,0103 physical sciences ,turbulent flow ,Fluid Flow and Transfer Processes ,Physics ,Turbulence ,Mechanical Engineering ,Mechanics ,Secondary flow ,secondary flow ,020303 mechanical engineering & transports ,Particle image velocimetry ,Flow (mathematics) ,flow separation ,exhaust flow ,Proper orthogonal decomposition ,reversed flow ,pulsatile flow - Abstract
The present experimental study deals with a pulsatile turbulent flow simulating the exhaust flow of an automotive engine. In the experiments, a four-cylinder engine is used as an exhaust-flow generator to realize flow conditions close to those in an engine environment. Particle image velocimetry (PIV) measurements visualize the flow field in an S-shaped double-bend duct at a Reynolds number of 48,000 and a Womersley number of 70.9. Stereo PIV, which is classified as a two-dimensional three-component measurement, is conducted in the duct cross sections located downstream of the bends. The stereo PIV system is synchronized with the engine operation to enable phase-locked measurements at particular phases, and the phase-averaged results show the large-scale vortical structures and the duct axial velocity distribution. Downstream of the first bend, the secondary flow consists of vortices that circulate as Dean-type vortices. Downstream of the second bend, by contrast, vortices that circulate in opposite directions to the Dean-type vortices, so-called Lyne-type vortices, form in the core of the cross section. These secondary flows persist without significant changes in their large-scale vortical structures over time. Time-resolved PIV is conducted to track the temporal evolution of the flow in the bend planes. The results show that the flow reverses locally along the inner wall of the bends during flow deceleration. Snapshot proper orthogonal decomposition (POD) is used on the time-resolved PIV data to extract the significant flow structure from the instantaneous field. We propose POD as a good post-processing tool for the instantaneous data of pulsatile cases.
- Published
- 2018
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