scholarly journals Stereo PIV measurements of oscillatory plasma forcing in the cross-plane of a channel flow

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Marc T. Hehner ◽  
Lars H. Von Deyn ◽  
Jacopo Serpieri ◽  
Saskia Pasch ◽  
Timo Reinheimer ◽  
...  
Keyword(s):  
Channel Flow ◽  
Particle Image ◽  
Dynamic Range ◽  
Turbulent Channel Flow ◽  
Plasma Actuator ◽  
Piv Measurements ◽  
Stochastic Fluctuations ◽  
Image Velocimetry ◽  
Field Dynamic ◽  
Stereo Particle Image Velocimetry

The present work describes an experimental investigation that applies stereo particle image velocimetry in a cross-plane of a turbulent channel flow that is additionally perturbed by spanwise oscillatory body forces, induced by a plasma actuator and designed to mimic the effect of spanwise wall oscillations. The experiment is aimed at retrieving the forcing-correlated scales and the turbulent flow stochastic fluctuations for the measured cross-plane. The first are macroscopic scales and require a larger investigation domain while the latter benefit of a higher resolution. Furthermore, the extended flow-field dynamic range posed a challenge on the experiment design, finally leading to an optimal tradeoff. The results of the unactuated flow compare well to the direct numerical simulations of Hoyas and Jimenez ́ (2008), while the actuated case demonstrates strong near-wall momentum addition and spanwise modulation of the streamwise flow component.

Particle-Image Velocimetry Investigation of an Oscillating Turbulent Channel Flow

2008 ◽  
Author(s):  
Sean Kearney ◽  
Timothy O'Hern ◽  
Thomas Dimiduk ◽  
Thomas Grasser ◽  
Jermey Barney ◽  
...  
Keyword(s):  
Particle Image Velocimetry ◽  
Channel Flow ◽  
Particle Image ◽  
Turbulent Channel Flow ◽  
Image Velocimetry

scholarly journals On the Effects of Tip Clearance and Operating Condition on the Flow Structures Within an Axial Turbomachine Rotor Passage

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Yuanchao Li ◽  
Huang Chen ◽  
David Tan ◽  
Joseph Katz
Keyword(s):  
Particle Image ◽  
Suction Side ◽  
Tip Clearance ◽  
Flow Structures ◽  
Narrow Gap ◽  
Piv Measurements ◽  
Tip Leakage ◽  
Image Velocimetry ◽  
Stereo Particle Image Velocimetry ◽  
Turbomachine Rotor

Abstract Effects of tip clearance size and flowrate on the flow around the tip of an axial turbomachine rotor are studied experimentally. Visualizations and stereo-particle image velocimetry (PIV) measurements in a refractive index-matched facility compare the performance, leakage velocity, and the trajectory, growth rate, and strength of the tip leakage vortex (TLV) for gaps of 0.49% and 2.3% of the blade chord, and two flowrates. Enlarging the tip clearance delays the TLV breakup in the aft part of the rotor passage at high flowrates but causes earlier breakup under pre-stall conditions. It also reduces the entrainment of endwall boundary layer vorticity from the separation point where the leakage and passage flows meet. Reducing the flowrate or tip gap shifts the location of the TLV detachment from the blade suction side (SS) upstream to points where the leakage velocity is 70–80% of the tip speed. Once detached, the growth rates of the total shed circulation are similar for all cases, i.e., varying the gap or flowrate mostly shifts the detachment point. The TLV migration away from the SS decreases with an increasing gap but not with the flowrate. Two mechanisms dominate this migration: initially, the leakage jet pushes the TLV away from the blade at 50% of the leakage velocity. Further downstream, the TLV is driven by its image on the other side of the endwall. Differences in migration rate are caused by the smaller distance between the TLV and its image for the narrow gap, and the increase in initial TLV strength with decreasing flowrate and gap.

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