Browsing by Author "Hinman, William Schuyler"

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    Laminar Near Wake of Hypersonic Blunt Bodies
    (2017) Hinman, William Schuyler; Johansen, Craig; Martinuzzi, Robert; Wood, David; Cully, Christopher; Chue, Randy
    A detailed analysis of the mechanisms of the hypersonic laminar near-wake is presented. Simulations of the compressible Navier-Stokes equations in two dimensions for various geometries (a cylinder, sphere, and a truncated aft-body cylinder) at a range of Mach (6
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    Laser Sintering of Thin PZT Film for Sensing Applications
    (2023-01-26) Chuo, Yu Sung; Park, Simon; Tiamiyu, Ahmed A.; Dalton, Colin; Hinman, William Schuyler
    The discovery of piezoelectric effect has inspired sensor integration. For these applications, the thinness and flexibility of the sensor are key elements because the easily adaptable use of the sensor would benefit the widespread adoption. Thin ceramic-based piezoelectric sensor is advantageous compared to bulk piezoceramic and polymer sensors when it comes to impact on dynamics measurement, due to the minimal alteration to the system under measurement, and higher frequency bandwidth, provided by the low mass and high stiffness, while satisfying constraints in tight spaces. Lead zirconate titanate (PZT) sensor has traditionally been thermally sintered using a furnace. However, this process consumes large amount of time and energy, requiring many hours and heating of the entire chamber. In this investigation, thin PZT underwent laser sintering, whose localized heating reduces time and energy requirements. Furthermore, CNT/PZT nanocomposite film was prepared in which PZT particles were mixed with carbon nanotubes (CNT) to improve the strength and sintering efficiency, utilizing the mechanical and thermal properties of CNT. Laser processing was optimized by alternating the control parameters, material compositions, and deposition height. A multi-physics finite element modelling was performed to approximate the temperature of the sintering process. Sintered films were obtained and were electrically poled to enhance the piezoelectric property. The effectiveness of laser sintering was assessed with and without CNT. The piezoelectric coefficient of laser sintered PZT increased by approximately 10 fold compared to unsintered PZT. Due to CNTs acting as a reinforcement phase and sintering aid, PZT films containing 0.5 wt% CNTs displayed higher strength compared to PZT films without CNTs after laser sintering, while using less sintering energy. The CNT addition made a compromise on piezoelectric property compared to laser sintered PZT, but still at a high level which is easily utilizable. Based on these results, laser sintering can be effectively used to enhance piezoelectric and mechanical properties of PZT and CNT/PZT films, in smaller turnaround period and energy budget.
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    Multi-fidelity Aerodynamic Analysis of Outboard Horizontal Stabilizers for Small-scale Aircraft
    (2024-12-18) De Alwis, Arjuna; Hinman, William Schuyler; Limacher, Eric John; Benneker, Anne
    The Outboard Horizontal Stabilizer (OHS) configuration is a unique fixed-wing design often used when a traditional tail is impractical and has been proposed as a means to achieve enhanced range and endurance. This study utilized a mixture of numerical approaches to quantify and critically examine the potential performance gains of the OHS concept. A modified non-linear lifting-line approach incorporating wing interactions was used for a fast low-fidelity model, and Reynolds Averaged Navier Stokes simulations were completed using OpenFOAM. A representative small-scale wing-tail combination was arranged into traditional, outboard, split, and extended span configurations and was used as a case study. The results obtained in this work demonstrate a substantial increase in Cl/Cd and Cl^{3/2}/Cd ratios for the OHS when compared to configurations with a similar main wing span, correlating to increased range and endurance, respectively. However, it was observed that simply extending the main wing to the overall span of the OHS configuration yielded higher performance. The importance of performing an aerodynamic analysis while considering static stability and trim is also discussed in detail. Furthermore, the specific conditions that can lead to increased overall lift and reduced induced drag on the stabilizers are highlighted and discussed using different approaches, and a qualitative analysis of the wake flow field was used to explain and confirm conclusions. Finally, a focused parametric study was performed to analyze how stabilizer position and deflection impact aerodynamic performance. It was found that for a fixed tail arm, having the tail just outboard of the main wing would maximize the performance of an OHS configuration. It was further found that the lift-to-drag ratio of an OHS configuration may surpass that of a conventional configuration with the same overall span if the fraction of tail span is reduced while increasing the tail arm, in order to maintain stability. Future studies will focus on a comprehensive optimization analysis to examine when and how OHS configurations may outperform optimal conventional configurations.
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    Turbulent Combustion Modeling of an Ejector Ramjet Propulsion System
    (2024-08-12) Migadel, Tyson; Johansen, Craig; Korobenko, Artem; Hinman, William Schuyler; Benneker, Anne Maria
    The Atlantis Intake System (AIS) is a novel design for a ramjet inlet intended to produce thrust through a wide range of flight Mach numbers, including at static conditions, by operating as an ejector-ramjet. A computational fluid dynamics study is performed to assess the change in performance of the AIS due to preheating the fuel jet using heat released from combustion. However, first the computation model is assessed for several combustion-related problems relevant to an ejector ramjet: a one-dimensional laminar flame, a three-dimensional bluff-body stabilized flame, and a ramjet with the AIS operating at static conditions. For an ejector ramjet, preheating the fuel jet is shown to increase the ratio of air to fuel entrained by the AIS and the specific impulse (ISP). Furthermore, if the global equivalence ratio is above unity, preheating the fuel jet while keeping the fuel jet stagnation pressure constant results in an increase in thrust. In contrast, the thrust is lowered as the stagnation temperature of the fuel jet is increased for cases with lean combustion if the stagnation pressure of the fuel is kept constant.