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 T38: Vortex Dynamics and Vortex Flows: Turbulence |
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Chair: Robert Martinuzzi, University of Calgary Room: 355 D |
Monday, November 25, 2024 4:45PM - 4:58PM |
T38.00001: THREE-DIMENSIONAL, NONLINEAR, INSTABILITY OF THE BURGERS VORTEX Basak Cakmak, Greg Lewis, Lennaert Van Veen, Andrew Hazel Burgers' vortex is one of the few analytically known, three-dimensional, vortical solutions to the Navier-Stokes equations. It relies on vortex stretching, thought to be one of the sustaining mechanisms of turbulence. Remarkably, this solution has been shown to be linearly stable. At the same time, there are theoretical indications that families of less symmetric solutions and more realistic equilibrium vortical flows exist near Burgers' solution. We explore the phase space around Burgers' flow by direct numerical simulations of finite-sized perturbations for low and intermediate Reynolds numbers, relying on the finite element code OOMPH-LIB for time-stepping as well as for the computation and continuation of equilibria and their spectra. |
Monday, November 25, 2024 4:58PM - 5:11PM |
T38.00002: Abstract Withdrawn
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Monday, November 25, 2024 5:11PM - 5:24PM |
T38.00003: Abstract Withdrawn
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Monday, November 25, 2024 5:24PM - 5:37PM |
T38.00004: Direct numerical simulations of a cylinder cutting a vortex Rodolfo Ostilla Monico, Steven Soriano The interaction between a vortex and an impacting body which is oriented normally to it is complex due to the interaction of inviscid and viscous three-dimensional mechanisms. To model this process, direct numerical simulations of a thin cylinder intersecting a columnar vortex oriented normally to it are conducted. By varying the impact parameter and the Reynolds number, the two regimes of interaction mentioned in the literature are distinguished: the weak and strong vortex regimes. Low impact parameters, representing strong vortices, led to ejection and interaction of secondary vorticity from the cylinder's boundary layer, while high impact parameters, representing weak vortices, led to approximately inviscid interaction of the cylinder with the primary vortex through deformations. No significant effect of the Reynolds number in the overall phenomenology is found, even if larger Reynolds numbers lead to the formation of increasingly smaller and more intense vortex structures in the parameter range studied. Finally, the hydrodynamic force curves on the cylinder are analyzed, showing that intense forces could be locally generated for some parameter regimes, but that the average force on the cylinder does not substantially deviate from baseline cases where no vortex was present. Our results shed light on the underlying mechanisms of vortex-body interactions and their dependence on various parameters. |
Monday, November 25, 2024 5:37PM - 5:50PM |
T38.00005: On the negative production in the cylinder wake using triple decomposition Kwanho Ree, Jin Hwan Hwang Two-dimensional and two-component velocity fields of cylinder wakes were measured through laboratory experiments using particle image velocimetry (PIV). Proper orthogonal decomposition (POD) was applied to the measured data to extract the unsteady coherent motion of the cylinder wakes. The combination of the first and the second modes was assumed to be the unsteady coherent motion of cylinder wakes, and the summation of the rest of the fluctuation components was denoted as turbulent fluctuation. Similarly, decomposing an original velocity into the time average, unsteady coherent motion, and turbulent fluctuation is a decomposition methodology called triple decomposition. |
Monday, November 25, 2024 5:50PM - 6:03PM |
T38.00006: Analysis of vorticity flux during laminar-turbulence transition in channel flow Seungchank Kim, Donghyun You In channel flow, the wall-normal flux of spanwise vorticity is directly related to drag and energy dissipation. This flux starts from the wall and persists to the channel centerline, sustained by diffusive and advective transport. We investigate the contributions to this vorticity flux during transition from laminar flow, where the flux is entirely viscous, to turbulent flow, where viscous, advective, and stretching/tilting effects all contribute. Ensemble-averaged statistics of K-type and H-type transition are computed, and the analysis focuses on the nonlinear contribution (advective and stretching/tilting term) to the vorticity flux profile during the transition process. How these terms change is explained with reference to the changes in the base flow. In terms of flow structures, the lambda-shaped vortices that are observed prior to reaching the fully turbulent state are also examined, and they feature both upgradient and downgradient flux of vorticity. Conditionally sampled structures are also computed to distinguish the contributions to the upgradient and downgradient transport of spanwise vorticity. |
Monday, November 25, 2024 6:03PM - 6:16PM |
T38.00007: Hybrid study of Vortex Lines in Transitional Pipe Flow Cole Cooper, Scott West, Dustin P Kleckner Concentrated vortex lines spontaneously arise in many flows -- such as turbulence -- acting as organizing features of the flow. In order to study the interactions between vortices and background flows in a controlled environment, we have built an experimental apparatus to generate and track streamwise vortices in pipe flow at Reynolds numbers up to 2000. We image the resulting flows in 3D using a combination of fluorescently dyed vortex cores and randomly distributed tracer particles. Our experimental results are compared to a Navier-Stokes simulation of the same scenario. Our setup allows us the unique opportunity to analyze 3D flow fields in experiments and simulations using identical methods. This research extends the geometric analysis of vortices into more dynamic flow environments. |
Monday, November 25, 2024 6:16PM - 6:29PM |
T38.00008: Numerical simulations of vortex lines in transitional pipe flow Scott West, Cole Cooper, Dustin P Kleckner, maxime theillard Concentrated vortex lines appear in many flows, such as aerodynamics, turbulence, and weather systems. Although significant past work has focused on understanding the behavior of isolated vortices, the interaction of vortices with walls and shear flows also plays an important role in many systems. To study these interactions, we have developed tools to simulate an experiment which generates streamwise vortices in pipe flow at the laminar/turbulent transition regime. Our simulations employ a second-order projection method with adaptive octree grids and supra-convergent finite difference schemes to solve the incompressible Navier-Stokes equations across a wide range of Reynolds numbers. We use a level-set formulation and efficient tree-traversal algorithms to represent the realistic solid obstructions that are used in these experiments. A key feature of our simulation toolbox is the ability to augment and fine-tune the solver to match the experimental apparatus, allowing us to visualize and compare our results with experimental data easily. |
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