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

Kristo, Paul; Kimber, Mark

doi:10.1007/s00348-021-03159-x

Cited by 2 publications

(12 citation statements)

References 55 publications

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“…Instantaneous and time-averaged velocity magnitude profiles of the xz plane at y/D = 1 have been observed previously in [15,44] and are reproduced here in Figures 3 and 4. The single jet profiles in Figure 3a-c appear amorphous, as a result of the aggregation of Both the crossflow and jets are seeded sequentially using a TSI Six Jet Atomizer (TSI Incorporated, Shoreview, MN, USA) with Dioctyl Sebacate tracer particles.…”

Section: Description Of Data Setssupporting

confidence: 80%

“…Instantaneous and time-averaged velocity magnitude profiles of the xz plane at y/D = 1 have been observed previously in [15,44] and are reproduced here in Figures 3 and 4. The single jet profiles in Figure 3a-c appear amorphous, as a result of the aggregation of several mechanisms induced by the two perpendicular flow streams and boundary layer interactions with the wall leading up to the jet.…”

Section: Description Of Data Setssupporting

confidence: 80%

“…Full details regarding the experimental arrangement have been outlined previously [15,44] with pertinent details reviewed here. The experiment consists of a low speed wind tunnel test section with three round jets in a tandem formation issuing vertically downward from the ceiling of the test section as outlined in Figure 2.…”

Section: Description Of Data Setsmentioning

confidence: 99%

“…The tandem jet configuration further complicates these interactions as the flow driving mechanisms become less clear, exhibiting more localized features as a result of the spatial proximity of each jet. Reproduced with permission from Kristo and Kimber, Time-resolved particle image velocimetry measurements of a tandem jet array in a crossflow at low velocity ratios [15]; published by Springer Nature, 2021. Reproduced with permission from Kristo and Kimber, Time-resolved particle image velocimetry measurements of a tandem jet array in a crossflow at low velocity ratios [15]; published by Springer Nature, 2021.…”

Section: Description Of Data Setsmentioning

confidence: 99%

“…However, no effort is provided here. In Section 4, the methodology is applied to time-resolved particle image velocimetry (TR-PIV) data of a single and three tandem round jets in a crossflow, where the latter exhibits complicated secondary interactions as a result of shielding provided by each jet with its neighbor(s) [15]. The cross-sectional plane measurements of the single and tandem jet arrays share the same general physical features and phenomena and constitute the unit and complex flows, respectively.…”

Section: Introductionmentioning

confidence: 99%

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Towards Reconstruction of Complex Flow Fields Using Unit Flows

Kristo

Kimber

Girimaji

2021

Fluids

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Many complex turbulent flows in nature and engineering can be qualitatively regarded as being constituted of multiple simpler unit flows. The objective of this work is to characterize the coherent structures in such complex flows as a combination of constituent unitary flow structures for the purpose of reduced-order representation. While turbulence is clearly a non-linear phenomenon, we aim to establish the degree to which the optimally weighted superposition of unitary flow structures can represent the complex flow structures. The rationale for investigating such superposition stems from the fact that the large-scale coherent structures are generated by underlying flow instabilities that may be reasonably described using linear analysis. Clearly, the degree of validity of superposition will depend on the flow under consideration. In this work, we take the first step toward establishing a procedure for investigating superposition. Experimental data of single and triple tandem jets in crossflow are used to demonstrate the procedure. A composite triple tandem jet flow field is generated from optimal superposition of single jet data and compared against ‘true’ triple jet data. Direct comparisons between the true and composite fields are made for spatial, temporal, and kinetic energy content. The large-scale features (obtained from proper orthogonal decomposition or POD) of true and composite tandem jet wakes exhibit nearly 70% agreement in terms of modal eigenvector correlation. Corresponding eigenvalues reveal that the kinetic energy of the flow is also emulated with only a slight overprediction. Temporal frequency features are also examined in an effort to completely characterize POD modes. The proposed method serves as a foundation for more rigorous and robust dimensional reduction in complex flows based on unit flow modes.

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Section: Description Of Data Setssupporting

confidence: 80%

“…Instantaneous and time-averaged velocity magnitude profiles of the xz plane at y/D = 1 have been observed previously in [15,44] and are reproduced here in Figures 3 and 4. The single jet profiles in Figure 3a-c appear amorphous, as a result of the aggregation of several mechanisms induced by the two perpendicular flow streams and boundary layer interactions with the wall leading up to the jet.…”

Section: Description Of Data Setssupporting

confidence: 80%

Section: Description Of Data Setsmentioning

confidence: 99%

Section: Description Of Data Setsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Towards Reconstruction of Complex Flow Fields Using Unit Flows

Kristo

Kimber

Girimaji

2021

Fluids

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Cylinders and jets in crossflow: Wake formations as a result of varying geometric proximities

Kristo

Kimber

2021

Physics of Fluids

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The combined flow physics of several canonical flow configurations is experimentally studied. Here, we analyze an array of jets issuing into a crossflow, then immediately navigating past an array of cylinders. This is achieved with a 2 × 3 triangular pattern of jets and symmetric cylinders at three jets to crossflow velocity ratios, enabling near-complete optical access of each jet, with velocities measured by time-resolved particle image velocimetry. Jet trajectories reveal that each configuration adheres to a power-law trend and that greater penetration is achieved by the downstream and confined jets compared to the more conventional upstream one. Recirculation regions of the upstream and downstream jets are nearly independent, with the confined jet encompassing regions of overlap with both. Turbulent statistics reveal the influence of geometric placement and velocity ratio on the time-averaged velocity, anisotropy, and Reynolds stresses incurred by each jet. Galilean decomposition utilizes a supplemental crossflow-only velocity field to delineate the influence of each jet's low- and high-pressure regions on the otherwise uniform stream. Proper orthogonal decomposition suggests that increased jet penetration decreases the number of modes required for truncation in the investigated spanwise plane. Vortex identification algorithms are applied to the reconstructed flow fields, reaffirming that with increasing velocity ratio, the jets generate vortices of their own in similar statistical formations as the cylinders. This investigation provides a foundation to aid future modeling efforts toward characterizing flow physics of importance in designing and passively controlling transverse jets with varying blockage proximities in a crossflow.

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

Cited by 2 publications

References 55 publications

Towards Reconstruction of Complex Flow Fields Using Unit Flows

Towards Reconstruction of Complex Flow Fields Using Unit Flows

Cylinders and jets in crossflow: Wake formations as a result of varying geometric proximities

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