Bulletin of the American Physical Society
77th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 24–26, 2024; Salt Lake City, Utah
Session J39: Turbulent Jets |
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Chair: Kostas Steiros Room: 355 E |
Sunday, November 24, 2024 5:50PM - 6:03PM |
J39.00001: Simulating a Variable Density Jet with Negative Turbulent Kinetic Energy Production Vincent P Chiravalle, Tiffany R Desjardins, John J Charonko Experiments with a variable density, turbulent jet in coflow by Charonko & Prestridge (2017) have observed negative turbulent kinetic energy production. While backscattering of energy is known to occur in turbulent flows exhibiting a conventional forward cascade, in this variable density jet a net transfer of energy from the fluctuations to the mean flow takes place as demonstrated by Lai, Charonko, & Prestridge (2018). It is a challenge to represent this kind of jet using many Reynolds-Averaged Navier-Stokes (RANS) models available in the literature. Prior simulations with established RANS methods have shown excessive spreading of the jet relative to the experiment. One promising method which could potentially overcome this challenge is a recently developed de-mix capable RANS model for compressible, variable density flows, based on the Besnard-Harlow-Rauenzahn (BHR) family of models. BHR-4 differs from previous BHR models in that it evolves additional turbulent correlations associated with fluctuations in species mass fraction. This work simulates the variable density jet using the BHR-4 model and compares the results to earlier versions of BHR in order to see if these additional turbulent correlations better represent the jet. |
Sunday, November 24, 2024 6:03PM - 6:16PM |
J39.00002: A new scaling for turbulent, twin round jets Joseph Mathew, Taye M Taddesse The flow field due to a pair of identical uniform round jets emerging from ports in a plane wall depend on the jet velocity U, port diameter d, and port separation S. At Reynolds numbers Ud/ν that are O(1000) or larger, these jets will breakdown into turbulence. The jets grow downstream and merge to have an elliptical cross-section that will develop into a single circular jet downstream. From LES of such configurations at Re of 25000, and 230000 of two experiments and 2 < S < 8, we observed the mean axial velocity to rise to a peak U0 at distance L0 from the inflow plane wall, and thereafter to fall off smoothly. U0 decreases and L0 increases with S. For all nozzle spacings, a similar development was observed: Uc/U0 is a function of axial distance x/L0 only, and is essentially independent of jet spacing S/d, and Re. Since U0 and L0 depend linearly on inflow plane parameters, near-fields of all twin round jets can be predicted from one solution. |
Sunday, November 24, 2024 6:16PM - 6:29PM |
J39.00003: Azimuthal Decomposition of Turbulent Fluctuations in a Round Jet near the Nozzle Exit and Far Downstream Amaru A Ordóñez-Jacobson, Gao Jun Wu, Sanjiva K Lele As interest grows in innovating commercial supersonic aircraft, accurate modeling of jet noise from engine exhaust is crucial for manufacturers and regulatory bodies. Existing prediction tools for jets from conical nozzles typically use simplified noise source models based on statistical averaging and symmetry assumptions of turbulence fluctuations. However, these assumptions may not adequately account for the aeroacoustic effects of instability waves in the shear layer near the nozzle or the intermittent bursts of fluctuations downstream of the potential core. This could explain why noise prediction models are less accurate for upstream noise emission and spectra outside the mid-St range (St < 0.2 or St > 1). |
Sunday, November 24, 2024 6:29PM - 6:42PM |
J39.00004: Study of a Synthetic Jet as a Building Block for Turbulence Facilities Rhett Parry, Tim Berk Our work studies the development of multi-orifice synthetic jets (SJs). We show that scaling arguments for our multi-orifice jet are consistent with the development of a single-orifice SJ. In the context of using these SJs as actuators in a turbulence box, we focus on optimizing the turbulent kinetic energy (TKE). TKE is not typically investigated, with most literature focusing on velocity profiles and development. Our hexagonally packed orifice geometry minimizes axis switching and develops into a merged axisymmetric jet. Because multiple orifices lead to more TKE-producing shear layer structures, our latest iteration of testing focuses on an increasing number of orifices. The maximum number of orifices that fit within the loud speaker diaphragm decreases with increasing orifice diameter, but a balance may be struck between number and size of the created shear layers. Additionally we use a pressure probe to track the usage of the jet reservoir. With increasing total orifice area we expect that the diaphragm will need to deflect more to compensate for a faster loss in pressure. The geometries and operating conditions for our SJ must thus be tuned to ensure an optimal level of turbulence is achieved in a facility which uses such SJs as building blocks for creating turbulence. |
Sunday, November 24, 2024 6:42PM - 6:55PM |
J39.00005: CFD-Based Pressure Solver for PIV Forest D Shaner, Walter C Smith, Alexander Mychkovsky Pressure reconstruction from PIV data is a powerful means to extract full-field pressure data from empirical measurements. In an effort to validate the time resolved reconstructed pressure fields from a flat plate synthetic jet impingement experiment in water, the PIV measurement volume was modelled and a CFD simulation was performed in Ansys CFX. The reconstructed pressure field from the PIV experiment was then compared to the output pressure field of the CFD solver as well as the reconstructed pressure field using the calculated velocity field from the CFD solver. Aside from the reconstructed pressure field, pressure transducer measurements taken at the center of the impingement plate were compared to the results of the CFD simulations. The synthetic jet experiment was performed at 3 different jetting frequencies: 10Hz, 5Hz, and 2.5Hz, each of which was simulated for 6 periods in CFX. |
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