10:20   PIV/PTV methods and applications I Characteristics of turbulence-induced gel in open channel turbulent flow of aqueous surfactant solutions with different Reynolds numbers Yusei Yabuuchi, Makusu Kida, Shumpei Hara Abstract: This study aims to clarify the influence of Reynolds number on the growth behavior and structural stability of turbulence-induced gels formed by dosing a surfactant solution through a permeable wall in an open-channel turbulent flow. Experiments were conducted under two Reynolds number conditions with different turbulence intensities. Using video imaging and image analysis, the gel’s growth and height fluctuations were visualized and quantified. The results showed that under higher Reynolds number conditions, the gel grew faster, extended more significantly, and exhibited larger fluctuations. These findings indicate that turbulence strength plays a critical role in the formation and dynamic behavior of the gel structure. Iterative domain partitioning in pressure from PIV Alex-Mihai Dontu, Fulvio Scarano, Abbas Daliri Abstract: A generalized technique for pressure reconstruction from PIV data is proposed that eliminates the need for user specified boundary conditions prior to pressure gradient integration. The method extends the dual model approach developed by Jux et. al. in 2020, which partitions the measurement domain into irrotational (IRR) and rotational (ROT) regions using the total pressure coefficient as a discriminant. The latter approach, however, suffers from dependence upon the initial choice of irrotational boundary conditions as well as the threshold value set for the total pressure coefficient. Here, partitioning of the flow domain is approached iteratively for a significant reduction of result sensitivity to the user choice of parameters. It is demonstrated that Iterative Domain Partitioning (IDP) reliably converges to define a boundary between IRR and ROT. The validity of the method is verified through comparisons with the state-of-the-art techniques applied to the steady flow over a NACA0015 airfoil at incidence. The results verify that IDP yields consistent results when varying the initial boundary conditions and the threshold of total pressure coefficient. Lagrangian Approach To Study Cross-Flow Vortices On A Cone Rotating In Still Fluid Abel George, Sumit Tambe Abstract: This work aims to study the instability and turbulence onset mechanism in rotating cone boundary layers by focusing on the coherent vortex structures that form close to the cone surface. Time-resolved 2C PIV and dye visualisation are used to study the instability-induced coherent vortices on a cone rotating in still water. The cone half angle is 30 degrees, which is known to induce both co-rotating and counter-rotating vortices, suggesting a mixed presence of cross-flow and centrifugal instabilities, respectively. The Finite-Time Lyapunov Exponent (FTLE) field, which quantifies the rate of separation of nearby fluid particles over a finite time, was computed to identify Lagrangian Coherent Structures (LCS). These structures are used to track the transport of coherent vortices in the flow. The preliminary results presented. The results are scaled using the G¨ortler Number along the cone surface and the diffusion length scale perpendicular to it.

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