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

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Abstract

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 crossflow velocity ratios in the range from 0.9 to 1.7. Previous studies have shown that for high ratios (\(\ge\) 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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Acknowledgements

The authors gratefully acknowledge support from Nuclear Energy University Program (NEUP) through the following projects: NEUP 12-3582 entitled “Experimentally Validated Numerical Models of Non-Isothermal Turbulent Mixing in High Temperature Reactors”. NEUP 15-8627 “Experimental Validation Data and Computational Models for Turbulent Mixing of Bypass and Coolant Jet Flows in Gas-Cooled Reactors”.

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Authors and Affiliations

  1. Department of Mechanical Engineering, Texas A&M University, AIEN M104, 423 Spence Street, College Station, Texas, 77843, USA

    Paul J. Kristo

  2. Department of Nuclear Engineering, Department of Mechanical Engineering, Texas A&M University, AIEN 205D, 423 Spence Street, College Station, Texas, 77843, USA

    Mark L. Kimber

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  1. Paul J. Kristo
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  2. Mark L. Kimber
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Correspondence to Mark L. Kimber.

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Appendix: Test cases

Appendix: Test cases

See Tables 3 and 4

Table 3 Experimental test conditions for the single jet in crossflow. For each element, three numbers imply conditions for velocity ratios \({{\varvec{V}}}_{{\varvec{J}}}/{{\varvec{U}}}_{\boldsymbol{\infty }}\)=0.92, 1.26 and 1.70. If only one number is present in a given element, it is consistent across all three velocity ratios tested
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Table 4 Experimental test conditions for the tandem jets in crossflow. The element values follow the same convention as Table 3
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Kristo, P.J., Kimber, M.L. Time-resolved particle image velocimetry measurements of a tandem jet array in a crossflow at low velocity ratios. Exp Fluids 62, 67 (2021). https://doi.org/10.1007/s00348-021-03159-x

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  • DOI: https://doi.org/10.1007/s00348-021-03159-x

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