Bulletin of the American Physical Society
75th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 20–22, 2022; Indiana Convention Center, Indianapolis, Indiana.
Session L22: Turbulence: Rotating Flows 
Hide Abstracts 
Chair: Xiang Yang, Pennsylvania State University Room: 208 
Monday, November 21, 2022 8:00AM  8:13AM 
L22.00001: Energy spectrum and interscale transfer in nonhomogeneous rotating flow: the case of a mixer Paul Beaumard, Pierre Bragança, Christophe Cuvier, Kostas Steiros, John Christos Vassilicos Timeresolved 2D2C PIV measurements are carried out in a water tank agitated by four blades rotating at constant speed. Different blade geometries with rectangular and fractallike shapes are tested in order to change the turbulence properties. In some runs, vertical bars (baffles) on the walls are used to break the rotation of the flow and see the impact on the results. 
Monday, November 21, 2022 8:13AM  8:26AM 
L22.00002: Data reconstruction of rotating turbulent flows with Gappy POD and Generative Adversarial Networks Tianyi Li, Michele Buzzicotti, Fabio Bonaccorso, Luca Biferale, Minping Wan, Shiyi Chen Two methods are used to reconstruct twodimensional instantaneous velocity module fields in a turbulent flow under rotation. The first method is Gappy POD, in which we use proper orthogonal decomposition (POD) to complete flow fields from gappy data, while the second one reconstructs the flow fields using convolutional neural networks embedded in a Generative Adversarial Network (GAN). We first show that there is always an optimal number of POD modes for Gappy POD reconstruction regarding a specific gap. In order to systematically compare the applicability of the two tools, we consider one square gap at the center with different gap sizes. Results show that compared with Gappy POD, GAN reconstruction not only has a smaller L2 error, but also better turbulent statistics of both the velocity module and the velocity module gradient. This can be attributed to the ability of nonlinearity expression of the network and the presence of adversarial loss during the GAN training. We also investigate effects of the adversarial ratio, which controls the compromising between the L2 error and the statistical properties. Finally, we access the reconstruction on random gappiness. Both methods perform well for small and medium gappiness, while GAN works better when the gappiness is large. 
Monday, November 21, 2022 8:26AM  8:39AM 
L22.00003: Effects of boundary conditions on the dynamics of convectiondriven plane layer dynamos. Souvik Naskar, Anikesh Pal Rapidly rotating convectiondriven dynamos are investigated under different kinematic and magnetic boundary conditions using direct numerical simulations. At a fixed rotation rate, represented by the Ekman number, E=5×10^{7}, the thermal forcing is varied from 2 to 20 times its critical value (R=Ra/Ra_c=220, where Ra is the Rayleigh number), keeping the fluid properties constant (Pr=Pr_m=1, where Pr and Pr_m are the thermal and magnetic Prandtl numbers. For R=3, the horizontal and vertical velocities are higher with noslip conditions compared to freeslip conditions at the wall. The structure and strength of the magnetic field produced by the dynamos, especially near the walls, depend on both velocity and magnetic boundary conditions. Though the leadingorder force balance in bulk remains geostrophic, the Lorentz force becomes comparable to the Coriolis force inside the thermal boundary layer with noslip, electrically conducting conditions. We also find enhanced heat transfer in the rotating dynamo convection, as compared with nonmagnetic rotating convection, with the peak enhancement lying in the range R=34. The dynamo action may significantly enhance the heat transport for freeslip conditions by suppressing largescale vortex formation. However, the peak enhancement is found at R=3 with noslip, electrically conducting walls, which can be attributed to a local magnetorelaxation of the rotational constraint due to enhanced Lorentz force inside the thermal boundary layer. 
Monday, November 21, 2022 8:39AM  8:52AM 
L22.00004: Annular Geoinspired Soft Mixer Simone Scollo, Clement Nobili, Emmanuel Villermaux, Patrice Meunier A geoinspired soft mixer with application to bladeless bioreactors is studied. It is fitted with an internal cylinder in order to shine light within the reactors, in order to grow microalgae (dinoflagellates), when the concentration of cells is large (and hence the optical penetration depth is small). This mixer is an evolution of the cylindrical soft mixer (Meunier (2020), J. Fluid Mech. 903, A15), inspired by the precession of the Earth. It consists of an annular cavity rotating around its axis and is tilted from the vertical. The base flow is forced by the free surface to a global inertial flow (Kelvin modes). When the height of fluid is equal to a multiple of a halfwavelength, there is a resonance of the base flow. At the resonance the amplitude of the base flow is saturated by Ekman pumping, with a scaling proportional to the inverse of the square root of the Ekman number. Furthermore, for sufficiently large tilt angles and small Ekman numbers, the base flow triggers a parametric triadic instability involving interaction with two additional Kelvin modes. This instability promotes an efficient mixing within the annulus, with a shear rate of the order of 50% the angular velocity. However, this shear intensity is weaker than with a standard Rushton turbine classicaly used in stirred tank (approximately 5 times smaller), making of the annulus an appropriate bladeless mixer for largescale bioreactors. 
Monday, November 21, 2022 8:52AM  9:05AM 
L22.00005: Effect of swirl on linear formation of streaks in jets Quentin Chevalier, Lutz Lesshafft, Christopher M Douglas, André V Cavalieri, Peter Jordan Streaks in turbulent jets are a recent finding, dominating kinetic energy at low frequencies. It is an experimental result that is interesting in and of itself as one of the few coherent structures observed in this setting. Similar structures are known to be present and play a critical role in wallbounded transition to turbulence. We propose to investigate the linear dynamics of streak generation in swirling jets. We compute a turbulent baseflow from the RANS equations at high Reynolds number, then leverage resolvent and modal analysis to study linear amplification mechanisms of the turbulent jet. We study a 2D azimuthally decomposed geometry with a 3D incompressible flow, and look at the effect of swirl on the linear mechanisms that give rise to growth of streaks. We include a nozzle in the calculation and use an eddy viscosity obtained from our RANS calculation. 
Monday, November 21, 2022 9:05AM  9:18AM 
L22.00006: On the inertial LandauLevichDeryaguin problem over a rotating disc J John Soundar Jerome, Sébastien Thevenin, Mickaël Bourgoin, JeanPhilippe Matas

Monday, November 21, 2022 9:18AM  9:31AM Not Participating 
L22.00007: Numerical simulations of PlanoTaylorCouette flow Zhiyu Yang, Varghese Mathai The planeCouette flow and the TaylorCouette flow are two classical fluid dynamical systems that have been studied in great detail. However, the mechanism of how these two canonical flows may interact remains unexplored. Here we use a numerical method to simulate a flow geometry formed between sliding conveyor belts, which combines a linear, planeCouette region and a curved, TaylorCouette region. The geometry is mainly defined by the parameters L / r_{i} and (r_{o}r_{i}) / r_{i}, where r_{o}, r_{i} are the outer and inner radius of TaylorCouette region, and L is the length of linear planeCouette region. When L << r_{i}, this system reaches the limit of the TaylorCouette flow, while in the limit L >> r_{i} the planeCouette geometry is dominant. We explore the situation where the outer belt is fixed and only the inner one is moving, and quantify the torque and drag for varying L / r_{i}. We draw insights about how the flow transitions from one limit to the other, with changing L / r_{i}, and within the merging zone. 
Monday, November 21, 2022 9:31AM  9:44AM 
L22.00008: Centrifugal assembly of helical fibers during microfluidic twisting Shankar P Kharal, Martin F Haase Centrifugal microfluidics has been widely used to integrate different processes such as separating, mixing, and detecting molecules at the nanoscale. Aside from these unit operations, an unrecognized use of the centrifugal effect is introduced during Microfluidic Twisting (MT). 
Monday, November 21, 2022 9:44AM  9:57AM 
L22.00009: Flows over a spinning disc at incidence Abdullah Kuraan, Omer Savas Flows normal to the surface of stationary finite discs exhibit distinct periodic motions in their wakes marked by regular shedding of looplike vortical structures. Most studies focus on the flows in the wake region; however, the present study focuses on the flows upstream and near the surface of spinning discs at incidence. Flows are studied over a range of angles of incidence, 0 ≤ α ≤ 36^{◦}, spinning at angular velocities, Ω = 0 & ± 6.2 rev/s, in a freestream velocity of U_{∞} = 2 m/s. The Reynolds number based on the diameter of the disc is 2.7 × 10^{4}. A smokewire technique is used for smoke visualization and a planar particle image velocimetry technique is used to make velocity measurements near the upstream surface. 
Monday, November 21, 2022 9:57AM  10:10AM 
L22.00010: Criteria for the asymptotic turbulence in rapidly rotating convection Jiaxing Song, Xiaojue Zhu Turbulent rotating convection is the primary source of heat and momentum transfers in planetary and stellar flows. Key control parameters–the viscosity and the thermal diffusivity–in the flows are extremely small. As a result, theories often assume the existence of an asymptotic diffusivityfree heat scaling in the rapidly rotating convection, where the heat flux is independent of viscosity and thermal diffusivity. It is believed that when this heat scaling is achieved, the whole system becomes asymptotic or fully turbulent. Here, by performing extensive direct numerical simulations, we show that despite that the heat scaling behaves asymptotic, the kinetic energy dissipation rate can still be viscosity dependent, indicating the whole system is not fully asymptotic yet. A straightforward revision that bridges such a gap is presented based on the exact relations that link the dissipation rates with the heat transfer. Besides the heat scaling, an asymptotic Reynolds number scaling and a convective length scaling can be derived as well. The extrapolation of the results to more extreme parameters is only possible when all the three scalings are satisfied and when the flow is fully turbulent. Most importantly, realizing the asymptotic heat scaling itself does not necessarily signal the onset of the asymptotic or fully turbulent state in rapidly rotating convection. 
Follow Us 
Engage
Become an APS Member 
My APS
Renew Membership 
Information for 
About APSThe American Physical Society (APS) is a nonprofit membership organization working to advance the knowledge of physics. 
© 2023 American Physical Society
 All rights reserved  Terms of Use
 Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 207403844
(301) 2093200
Editorial Office
1 Research Road, Ridge, NY 119612701
(631) 5914000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 200452001
(202) 6628700