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 ZC38: Vortex Dynamics and Vortex Flows: Applications |
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Chair: Mark Stremler, Virginia Tech Room: 355 D |
Tuesday, November 26, 2024 12:50PM - 1:03PM |
ZC38.00001: Vortex Dynamics Arising from Successive Vortex Rings Impacting Concave Asymmetric Cavities Tanvir Ahmed, Byron D Erath Tracheoesophageal (TES) speech is one of the most popular artificial voice rehabilitation techniques. During the production of TES, air passes through the tracheoesophageal prosthesis and enters the esophagus, generating successive vortex rings that impinge on the concave esophageal wall. A fundamental understanding of this fluid-structure interactions would help improve the success rate of TES, which is currently only 65%. This fundamental fluid-structure interaction also has applications to areas such as heat transfer enhancement and targeted fresh air supply. This study investigated the physics of successive vortex ring interactions with an asymmetric (hemicylindrical) concave cavity. Two successive vortex rings, referred to as leading and trailing, were generated with formation number of and Reynolds Number of using a piston-cylinder vortex ring generator inside a water tank. The frequency of the vortex ring generation was matched with that of TES. Three different ratios of vortex ring radius, Rv, to hemicylindrical cavity radius, Rcyl, were examined; namely, γ = Rv/Rcyl = 1/3, 1/2, and 2/3. Flow visualization and particle image velocimetry techniques were employed to quantify the interactions. Upon impact of the leading vortex ring on the cavity surface, secondary vorticity is generated. However, when the successive trailing vortex impacts the cavity wall, no secondary vorticity is generated despite the trailing vortex producing stronger wall-bounded vortices due to the vorticity sheet from the leading vortex ring. Aerodynamic loading on the structure is also estimated and discussed. |
Tuesday, November 26, 2024 1:03PM - 1:16PM |
ZC38.00002: Abstract Withdrawn
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Tuesday, November 26, 2024 1:16PM - 1:29PM |
ZC38.00003: Vortex-driven chemical species transport near a sharp corner Mohamed O Mahmoud Khattab, C.Nadir Kaplan We investigate how the advection and diffusion dynamics of a single chemical species are affected by Moffatt eddies, a low-Reynolds-number flow pattern emerging near a corner. To this end, we seek scale-free solutions to the 2D diffusion-advection equation to characterize the radial and angular dependence of the concentration field by using Moffatt's velocity profiles. The Lie symmetry method is used to analyze the 2D diffusion advection equation and obtain a similarity ansatz.The equation is then reduced into a 2nd order PDE in spatial variables only. This gives us a basic understanding of the role of advection and diffusion near singularities such as efficiency of chemical signal transport during protrusion formation inside a mesenchymal cell. |
Tuesday, November 26, 2024 1:29PM - 1:42PM |
ZC38.00004: Experimental and numerical study of flow passing through a series of angled plates Sajjad Hosseini, DongYeon Cheon, Wontae Hwang Air pollution capturing techniques have gained considerable attention over the past few decades as air pollution has significantly increased. For instance, selective catalytic reduction (SCR) systems eliminate nitrogen oxide (NOx) within a catalyst. Our previous studies have revealed that the uniformity of the flow entering the catalyst is a key factor in regards to efficiency. Often, flow straighteners are placed above the catalyst to straighten out the flow, turning around a corner. Thus, we intended to examine the effect of straightener ribs on flow uniformity in this research by utilizing particle image velocimetry (PIV) and large eddy simulation (LES). The flat straightener ribs are emulated by multiple parallel plates. Two variables are considered: the flow angle of attack and the separation distance between the plates. Compared to a single plate, the results illustrated a substantial difference in the wake size and shedding frequency, which varies from the first to last plate. This variation is due to multiple mechanisms related to the interaction of neighboring plates. The results are anticipated to provide insightful data and reveal mechanisms involved in the flow separation and vortex shedding from a straightener at an intermediate Reynolds number of 10,000. This will help design more efficient SCR systems. |
Tuesday, November 26, 2024 1:42PM - 1:55PM |
ZC38.00005: Resolvent analysis of flow inside a centrifugal pump Yonghong Zhong, Byungjin An, Motohiko Nohmi, Masashi Obuchi, Kunihiko Taira The near-tongue region of a centrifugal pump where the impeller and the volute meet plays a critical role in determining its overall performance and efficiency. The flow in this region is characterized by its complex unsteady behavior including flow separation and vortex shedding, which impact the pump operation. In this study, we employ resolvent analysis to investigate the unsteady flow dynamics in the near-tongue region of a centrifugal pump. Resolvent analysis allows us to identify the input and output modes about the baseflow. Here, the baseflow is taken to be the time-averaged turbulent flow in a two-dimensional centrifugal pump at $Re =\mathcal{O}$. Our findings reveal the existence of key modes and frequencies that govern the flow behavior in the near-tongue region. At below-nominal flow rate, the primary resolvent forcing and response modes appear inside of the tongue. On the other hand, when the flow rate is above nominal flow rate, the modal structures reside outside of the tongue. The identification of the resolvent modes and their frequencies has implications for potential design modification near the tongue. |
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