Bulletin of the American Physical Society
74th Annual Meeting of the APS Division of Fluid Dynamics
Volume 66, Number 17
Sunday–Tuesday, November 21–23, 2021; Phoenix Convention Center, Phoenix, Arizona
Session F19: Turbulence: Compressible |
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Chair: Katepalli Sreenivasan, New York University Room: North 132 ABC |
Sunday, November 21, 2021 5:25PM - 5:38PM |
F19.00001: Exploring near-continuum turbulent compressible flow in the Taylor-Green vortex Michael C Krygier, John R Torczynski, Michael A Gallis We investigate near-continuum turbulent compressible flow with non-continuum molecular gas dynamics (Direct Simulation Monte Carlo method) and continuum direct numerical simulations of the Navier-Stokes equations. We simulate compressible Taylor-Green vortex flow with polytropic initial conditions at five Mach numbers: 0.3, 0.6, 0.9, 1.2, and 2.0. At each Mach number, we compare kinetic-energy and energy-dissipation histories and velocity fields and spectra to assess the differences between the results from the two methods. The energy-decay histories are nearly identical, but molecular-level fluctuations break the symmetries of the initial condition and produce a different path from the initial nonturbulent flow to the long-time turbulent flow. |
Sunday, November 21, 2021 5:38PM - 5:51PM |
F19.00002: Energy exchange between solenoidal and dilatational motions in compressible isotropic turbulence Hang Song, Aditya S Ghate, Sanjiva K Lele In compressible turbulence, the dilatational motions and thermodynamic fluctuations become increasingly significant as Mach number increases and shocklets form. Understanding the mechanism of the energy transfer between solenoidal and dilatational motions is crucial in the study of compressible turbulent flows. This work follows Helmholtz decomposition of the velocity field and derives the budgets of the solenoidal and dilatational velocity variances for compressible turbulence. All terms in the budget equations are investigated using the direct numerical simulation data from a set of solenoidally forced compressible isotropic turbulence at different turbulent Mach numbers (M_{t}) with Reynolds number up to 170. The result shows that at low M_{t}, the terms in dilatational velocity variance equation oscillate about zero. As M_{t} increases, specific terms develop a bias in their statistical distribution and thus represent net variance transfer or exchange. The exchange processes are analyzed in detail at different Mach numbers both in physical space and in their statistical distribution. |
Sunday, November 21, 2021 5:51PM - 6:04PM |
F19.00003: Does dissipative anomaly hold for compressible turbulence? Diego A Donzis, John Panickacheril John, K. R Sreenivasan We systematically study dissipative anomaly in compressible turbulence |
Sunday, November 21, 2021 6:04PM - 6:17PM Not Participating |
F19.00004: Lie Symmetries of Characteristic Function Hierarchy in Compressible Turbulence Divya Sri Praturi, Dominik Pluemacher, Martin Oberlack Compressible turbulence is characterized by fluctuations in velocity as well as thermodynamic quantities. A unified framework to study flow and thermodynamics statistics in compressible turbulence is facilitated by a probability density function (PDF) or a characteristic function (CF) approach. In compressible flow regime, characteristic function offers advantages over its Fourier transform pair, the PDF. While the governing PDF equations are non-local in nature, CF equations do not contain any integral terms, thus simplifying the symmetry analysis. We compute the point-symmetries of the multi-point CF hierarchy by generalizing the symmetry groups obtained from single-, two- and three-point CF equations. As the CF equations are linear in nature, 'superposition principle' leads to two symmetry groups in addition to the ones seen in Euler equations. The validity of each of the symmetries at different fluid and flow parameters is discussed. We also present the group invariant solutions of various key statistics of compressible turbulence. |
Sunday, November 21, 2021 6:17PM - 6:30PM |
F19.00005: Signatures of compressibility of an annular free-shear layer with increasing Mach number Naoki N Manzano-Miura, Hazel T Rivera-Rosario, John Panickacheril John, Diego A Donzis, Gregory P Bewley The Variable Density and Speed of Sound Vessel (VDSSV) produces subsonic turbulent flows that are both compressible and observable at all scales with existing instrumentation including hot-wire anemometry. We raise the turbulent Mach number up to M_{t} = 0.17 at constant Reynolds numbers (up to R_{λ} = 1600) and while holding the boundary conditions fixed. We do this by comparing the flow of air with the flow of the heavy gas sulfur hexafluoride (SF_{6}), with a speed of sound almost three times lower than for air, downstream of a ducted fan. We show that the mean velocity profiles of the resulting turbulence approach a self-similar shape with increasing distance from the source. The jet responds like a compressible shear layer in the sense that it spreads more slowly at higher Mach numbers (up to M_{j} = 0.7) than at low Mach numbers. In contrast, the integral length scales and the Kolmogorov constant are approximately invariant with respect to changes in either the Reynolds or Mach numbers. |
Sunday, November 21, 2021 6:30PM - 6:43PM |
F19.00006: Quantifying density fluctuations in compressible turbulence Hazel T Rivera-Rosario, Naoki Manzano-Miura, Gregory P Bewley Numerical simulations show compressible shock-like structures at turbulent Mach numbers as low as 0.1. Quantifying the conditions that generate these structures is key to understanding how they behave in nature and engineered settings. Our goal is to quantify the density gradient field and to visualize shocks. We examine a turbulent jet inside a pressurized vessel with the ability to adjust the speed of sound using different gases including SF_{6}, reaching up to Re_{λ}~1000 and Ma_{t}~0.15. We perform Schlieren imaging and use the Gladstone-Dale relation to infer the density field from the image intensities. We visualize the turbulent jet flow and identify areas associated with large changes in density. These regions are then used to report spatial density gradient distributions and time-varying density fluctuations. With this information, we determine the frequency of highly compressive structures and validate published computer simulations. |
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