Proper orthogonal decomposition analysis of the large-scale dynamics of a round turbulent jet in counterflow

Rovira, Marc; Engvall, Klas; Duwig, Christophe

doi:10.1103/physrevfluids.6.014701

Cited by 8 publications

(3 citation statements)

References 26 publications

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“…However, as 𝐶 𝜇 increases, the forward flowfield becomes significantly asymmetric; SJ deflects downward (i.e., −𝑦 direction), and this deflection becomes more significant with the increase in 𝛽. This asymmetry is attributed to large radial oscillations caused by the strong shear interaction between the attributed to and the counterflow, which has been widely discussed in similar studies on turbulent jets in counterflows (e.g., Rovira et al, 2020Rovira et al, , 2021. In confined flow control applications, this asymmetry may exacerbate the blocking effect of the gap flow and lead to an increase in unbalanced forces on the controlled bluff body.…”

Section: Wake Flow Under Controlmentioning

confidence: 85%

Cylinder wake flow in confined channel and its active control by sweeping jets

Song,

Qiu,

Liu

et al. 2024

Preprint

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The wake dynamics of the flow past a confined circular cylinder and its active control by sweeping jets (SWJs) and steady jets (SJs) positioned at the front stagnation points were experimentally investigated using Particle Image Velocimetry (PIV) and pressure measurements. Experiments were conducted across a range of Reynolds numbers (Re) from 10,000 to 45,000 and blockage ratios (β) of \(1/2\), \(1/3\), \(1/4\), and \(1/5\). A comprehensive comparison between the current results and existing literature on natural flow dynamics fills the knowledge gap and reveals that confinement gradually reduces the time-average pressure coefficient (C_p) and increases the drag coefficient (\({C}_{D}\)) and Strouhal number (St). The interaction between the wake and wall shear layer gradually increased as \(\beta\) increased. Both SWJs and SJs effectively suppressed wake fluctuations, and the statistical characteristics of the flow field and Proper Orthogonal Decomposition (POD) analysis indicated a consistent flow control mechanism between the two methods. However, the SJs introduced external fluctuations and unbalanced forces in the forward flow field, resulting in a wake flow asymmetry. By contrast, SWJs provide more uniform control and superior flow control effectiveness and efficiency.

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Section: Wake Flow Under Controlmentioning

confidence: 85%

Cylinder wake flow in confined channel and its active control by sweeping jets

Song,

Qiu,

Liu

et al. 2024

Preprint

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“…To capture the relevant flow dynamics of the jet flow, we apply snapshot SPOD as reduced order modelling technique (24). Snapshot SPOD has already shown its capabilities for both swirling and non-swirling jet flows (21,28,29,32). The velocity field is decomposed into a mean and fluctuating part:…”

Section: Spectral Proper Orthogonal Decomposition (Spod)mentioning

confidence: 99%

Experimental study of a self-excited jet precession in a sudden expansion flow

et al. 2023

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Stereoscopic Particle Image Velocimetry (S-PIV) measurements are performed to analyse the flow field in a sudden expansion with an expansion ratio of 4.9:1. The velocity profile in the inlet tube is measured using Laser Doppler Anemometry (LDA) and the Reynolds number (Re) is varied from 3150 till 63300. The time-averaged flow field is found to be axisymmetric and has a jet-like velocity profile near the nozzle with a spreading rate comparable to free round jets. Despite the axisymmetric nature of the mean flow field, it contains unsteady coherent structures, which are analysed using both Spectral Proper Orthogonal Decomposition (SPOD) and phase averaging. It is found that the instantaneous flow field is asymmetric and it precesses around the central axis of the geometry. The structure of this precession is similar for all Reynolds numbers investigated and the Strouhal number increases with increasing Reynolds number till Re =26000, after which it reaches a constant value of around 3 × 10 −3 . These precessing structures were previously only reported for swirling sudden expansion flows or flows in dedicated free jet nozzles, but this study shows they also exist in confined nonswirling sudden expansion flows.

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“…The flow regimes have been identified due to the impingement of two fluids at room temperature [18][19][20][21][22][23][24][25][26]. Linear stability analysis was used to reveal the impingement of the laminar isothermal flows at a finite Reynolds number [24].…”

Section: Introductionmentioning

confidence: 99%

Quasi-direct numerical simulations of the flow characteristics of a thermal plasma reactor with counterflow jet

Zhang

Chen

et al. 2023

Plasma Sci. Technol.

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Three-dimensional quasi-Direct Numerical Simulations (q-DNS) have been performed to investigate a thermal plasma reactor with the counterflow jet. The effects of the momentum-flux ratio and distance between the counterflow jet and the thermal plasma jet on the flow characteristics are addressed. The numerical results show that the dimensionless location of the stagnation layer is significantly affected by the momentum-flux ratio, but it is independent on the distance. Specifically, the stagnation layer is closer to the plasma torch outlet with the increase of the momentum-flux ratio. Furthermore, the flow regimes of the stagnation layer and the flow characteristics of the thermal plasma jet are closely related to the momentum flux ratio. The characteristic frequencies associated with the different regimes are identified. The deflecting oscillation flow regimes are found when the momentum flux ratio is low, which provokes the axial velocity fluctuations inside the thermal plasma jet. By contrast, for the cases with high momentum flux ratio, the flapping flow regimes are distinguished. The thermal plasma jets are very stable and the axial velocity fluctuations mainly exist in the stagnation layer.

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Proper orthogonal decomposition analysis of the large-scale dynamics of a round turbulent jet in counterflow

Cited by 8 publications

References 26 publications

Cylinder wake flow in confined channel and its active control by sweeping jets

Cylinder wake flow in confined channel and its active control by sweeping jets

Experimental study of a self-excited jet precession in a sudden expansion flow

Quasi-direct numerical simulations of the flow characteristics of a thermal plasma reactor with counterflow jet

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