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 ZC33: Flow Control V: Passive |
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Chair: Panagiotis Theodorakis, Institute of Physics, Polish Academy of Sciences Room: 255 E |
Tuesday, November 26, 2024 12:50PM - 1:03PM |
ZC33.00001: How Do Nature-inspired Porous Fractal Parapets Change Rooftop Pressures over a Low-rise Building? Wei Zhang, Erick Shelley The increasing occurrence of severe wind events poses a growing threat, resulting in substantial fatalities and economic losses annually in the United States. Among affected civil structures, low-rise buildings are particularly vulnerable, as revealed by post-disaster surveys. The damage originates at windward corners and roof edges due to peak suctions induced by flow separation and conical vortices along rooftops. This study evaluates the efficacy of porous and nature-inspired cross-grid pattern fractal parapets with 40% porosity in mitigating rooftop suction on a 1:6 scale TTU building model for a near full-scale Reynolds number (Re = 0.92 x 106). Wind tunnel experiments at Florida International University's Wall of Wind facility involve four test cases: bare roof (no parapet), fractal parapet, and two porous parapet configurations with different strut thicknesses. The rooftop pressure statistics, the mean, rms, and peak pressure coefficients, are analyzed for several cornering wind directions. Overall, parapets exhibit effectiveness across all tested wind directions. In particular, the bio-inspired fractal parapet outperforms its counterparts, achieving peak suction reductions of about 90% depending on the wind direction. Using bio-inspired fractal cross-grid parapets is a promising passive flow control strategy to mitigate peak rooftop sections. This study contributes to ongoing efforts to find solutions to reduce damage and losses of low-rise buildings resulting from severe strong wind events. |
Tuesday, November 26, 2024 1:03PM - 1:16PM |
ZC33.00002: Passive Flow Control Using a Multi-Scale Approach Miguel Angel Olvera, Isaac Choutapalli This study investigates the impact of Triangular Prism Texturing (TPT) elements on the turbulent boundary layer characteristics of a flat plate, specifically analyzing changes in turbulent skin friction and flow separation. The analysis is based on data collected from Particle Image Velocimetry (PIV), comparing a baseline flat plate to one modified with TPT elements with a freestream velocity of 13 m/s. Results indicate that the TPT elements significantly alter the boundary layer dynamics by reducing the velocity defect and enhancing the velocity profile's fullness near the wall. This modification leads to a reduction in turbulent skin friction, as shown by a lower shear stress across the boundary layer. Additionally, the fuller velocity profiles suggest an increased momentum near the wall, enhancing the boundary layer's resistance to adverse pressure gradients and thus reducing the likelihood of flow separation. These findings demonstrate that TPT's can effectively improve the aerodynamic efficiency of surfaces by reducing drag and preventing flow separation, making it a promising technology for applications requiring optimized flow characteristics, such as in aerospace, automotive, and wind energy sectors. |
Tuesday, November 26, 2024 1:16PM - 1:29PM |
ZC33.00003: Aerodynamic Flow Control of a NACA 0018 Airfoil Using Triangular Porous Texturing Elements Eric Rodriguez, Luis Alvarez, Carl Tilmann, Isaac Choutapalli Passive flow control methods play a pivotal role in enhancing aerodynamic performance without the need for active energy inputs. This study investigates the effects of triangular porous textured (TPT) elements on the flow characteristics of a NACA 0018 airfoil. To do a comparative analysis, a baseline airfoil was used against the airfoil modified with the TPT elements to assess any change in the efficiency of the passive flow control device. The TPT elements are 1 mm equilateral triangular prisms, the spacing between the elements in any given row is 5mm (center to center of base) and the spacing between the rows is 4mm. The rows are staggered. The data collected was from a force balance connected at the trailing edge of each airfoil at midspan. Additionally, planar particle image velocimetry (PIV) data was collected at three-quarter span from each airfoil at pre-stall, stall, and post-stall angles of attack at several velocities. The goal of this experiment is to enhance aerodynamic performance through boundary layer control and flow control. The results are verified by completing a lift and drag comparison, a pitching moment analysis, and investigating the effectiveness of TPT’s on near-wall turbulence and flow separation using PIV and Computational Fluid Dynamics (CFD). |
Tuesday, November 26, 2024 1:29PM - 1:42PM |
ZC33.00004: Durotaxis and antidurotaxis motion on gradient substrates Panagiotis E Theodorakis, Russell Kajouri, Piotr Deuar, Rachid Bennacer, Jan Zidek, Sergei Egorov, Andrey Milchev By means of molecular dynamics simulation of a coarse-grained model, we explored the possibilities of causing the spontaneous motion of droplets onto brush and gel substrates with stiffness gradient, either in the direction of the gradient (durotaxis) or in the opposite direction (antidurotaxis). A detailed analysis of the driving force for durotaxis and antidurotaxis phenomena and an in-depth exploration of the relevant parameters are performed. We anticipate that our studies provide insights into the self-sustained motion of fluids onto gradient substrates with stiffness gradient and motivate further experimental research in this area. |
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