Browsing by Author "Desai, Siddhant"

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    Development of a low-cost flutter test bed with an EPS foam model for preliminary wing design
    Sanmugadas, Varakini; Miglani, Jitish; Zhao, Wei; Desai, Siddhant; Schetz, Joseph A.; Kapania, Rakesh K. (Elsevier France-Editions Scientifiques Medicales Elsevier, 2024-07)
    This paper discusses a novel, low-cost approach for the design and testing of a flutter test article made out of expanded polystyrene (EPS) foam. The low mass of this test article makes it especially suitable for serving as a test bed for similar low structure-to-fluid mass ratio wing configurations, though it could just as easily be used as the first step in the flutter testing of any structure with complex shape and mechanical properties. The material properties of EPS foam were tested using two different approaches: a 3-point bending test based on ASTM Standards for cellular materials and a new finite element model updating approach that used experimental data collected from simple ground vibration tests (GVT). It was found that the second approach provided material properties that were the most representative of the behavior of the specimen under flutter loads. That information was then used in a computational aeroelastic flutter model of the EPS foam wing. Wind tunnel flutter tests were performed for the EPS foam model. The computational frequency domain decomposition (CFDD) method was used to identify modal parameters and the damping trend extrapolating method was used to predict the critical flutter speed from pre-flutter experimental data. The flutter results from the aeroelastic model were in good agreement with the test data.
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    Wind Tunnel Testing of Tethered Inflatable Wings
    Desai, Siddhant; Schetz, Joseph A.; Kapania, Rakesh K.; Gupta, Rikin (AIAA, 2024-07)
    A wind tunnel testing approach for tethered inflatable wings is presented. Use cases for such wings range from airborne wind energy systems to high-altitude communication platforms. The tests were conducted for two tethered inflatable wings, one made out of nylon fabric and the other an ultra-high-molecular-weight polyethylene fabric. They were tested within a speed range of 15–32.5 m/s for three tether attachment configurations. Stereo photogrammetry data, force and moment measurements, and wake pressure measurements were recorded for each speed and test configuration. These measurements provide an experimental database for aeroelastic model validation and comparison with high-fidelity computational fluid dynamics studies. The effects of wing fabric material and tether attachment configurations on aerodynamic performance were explored and found to have a profound impact. These tests also highlight the possibility of passive aeroelastic tailoring of the wing configuration to achieve desired aerodynamic performance in the form of high lift and load alleviation. Some testing challenges and possible sources of measurement uncertainty are also discussed.