TR-PIV measurements and POD analysis of the plane wall jet subjected to lateral perturbation

Kaffel, Ahmed; Moureh, Jean; Harion, J.‐L.; Russeil, S.

doi:10.1016/j.expthermflusci.2016.04.001

Cited by 17 publications

(5 citation statements)

References 76 publications

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“…This is best attributed to the effects of new shear mechanisms promoted by the additional jets, with more localized eddies and swirling. In their study of the outer shear layer of wall jets, Kaffel et al (2016) have observed similar effects in their POD analysis, where their flow structures were significantly dominated by the streamwise direction. They confirmed the presence of additional coherent structures developing as a result of secondary instabilities in the spanwise direction.…”

Section: = φσψ (2)mentioning

confidence: 77%

Time-resolved particle image velocimetry measurements of a tandem jet array in a cross flow at low velocity ratios

Kristo¹,

Kimber²

2020

Preprint

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Investigation of the near field dynamics of a single and tandem array of three jets are provided by 2-D time-resolved particle image velocimetry (TR-PIV) measurements. Instantaneous velocity fields are examined in the transverse and spanwise planes with jet to cross flow velocity ratios in the range from 0.9 to 1.7. Previous studies have shown that for high ratios (≥2), the leading jet provides sufficient shielding to ensure that all jets downstream exhibit nearly identical flow characteristics. The current transverse plane measurements exhibit more unique and localized features as a result of the competing effects of pressure gradients and vortex mechanisms assessed via the jet exit profiles, first and second order turbulent statistics, streamline trajectories, recirculation areas, and penetrations depths. Proper orthogonal decomposition (POD) is applied to the spanwise plane instantaneous velocity fields to determine the statistically dominant features of the single and tandem jet configurations at equivalent velocity ratios. The velocity fields are then reconstructed using the truncated POD modes to provide further insight into the shear layer and wake vortices that drive these configurations. Vortex identification algorithms are applied to the reconstructed velocity fields to determine the statistical characteristics of the vortices, including their centroids, populations, areas, and strengths, each of which exhibit largely different dependencies on jet configuration and velocity ratio. Several of the investigated metrics are found to exhibit different behaviors below and above a velocity ratio of unity, and also as a function of increasing velocity ratio between 1 and 2, implying that several transitions mechanisms are present in the low velocity ratio regime investigated herein.

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Section: = φσψ (2)mentioning

confidence: 77%

Time-resolved particle image velocimetry measurements of a tandem jet array in a cross flow at low velocity ratios

Kristo¹,

Kimber²

2020

Preprint

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“…The LES Smagorinsky SGS model approach was adopted to resolve timewise and spacewise variation in the ow [22][23] . During simulations, the SIMPLE scheme, PRESTO!, the bounded central difference, the rst-order upwind are applied for pressure-velocity coupling, pressure-discretization, momentum discretization, and the volume fraction.…”

Section: Solution Methods and Convergence Criteriamentioning

confidence: 99%

Analysis of Transient Turbulent Flow in the Pilot Stage of a Deflector Jet Servo Valve

Wu,

Zou

2024

Preprint

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The performance of a deflector jet servo valve is highly affected by the characteristics of the pilot stage flow field. In this paper, the transient results of the large eddy simulation (LES)-based numerical simulation of the pilot stage flow field are presented. The LES results are validated against particle image velocimetry, showing that the LES method can predict the transient turbulent flow. The length of the potential core of the jet assuming from the nozzle and the position of the jet impinging on the V-groove have great relations with the inlet pressure. Traveling cavitation in the deflector begins to appear when the inlet pressure reaches 6 MPa. The increment in inlet pressure enhances cavitation and cavitation shedding. Snapshot proper orthogonal decomposition(snapshot POD) analysis, based on LES, is applied to decompose the instantaneous velocity fluctuation into coherent structures and turbulent velocity components. The relationships between each coherent structure and wall attachment flow, cavitation phenomena, and vortex pairs are discussed. The vortex in Mode 2 contributes to deflecting the jet from the nozzle and causing part of the fluid to flow along the side wall in the V-groove. Through the fast Fourier transform (FFT) result of the POD coefficient, it is known that the traveling cavitation near the side wall of the V-groove is related to Mode 4. This research contributes to the mathematical modeling and improving the stability of the flow field.

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“…Recently, POD method has been successfully applied for extracting the coherent structures in turbulent wakes, jets and channel flows (e.g. Feng et al 2011;Kaffel et al 2016; Qu et al 2017). It has also been used to reconstruct the lower order flow structures to reflect the dominant flow dynamics with the least number of modes (Bai et al 2019;Shi & Feng 2015;Tang et al 2015).…”

Section: Pod Analysismentioning

confidence: 99%

Vortex evolution in the near wake behind polygonal cylinders

Wang

Gan

et al. 2020

Experimental Thermal and Fluid Science

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TR-PIV measurements and POD analysis of the plane wall jet subjected to lateral perturbation

Cited by 17 publications

References 76 publications

Time-resolved particle image velocimetry measurements of a tandem jet array in a cross flow at low velocity ratios

Time-resolved particle image velocimetry measurements of a tandem jet array in a cross flow at low velocity ratios

Analysis of Transient Turbulent Flow in the Pilot Stage of a Deflector Jet Servo Valve

Vortex evolution in the near wake behind polygonal cylinders

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