Browsing by Subject "hypersonics"

Now showing 1 - 3 of 3
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    Design of the Sensor Pod of the Hypersonic Configurable Unit Ballistic Experiment (HyCUBE)
    (2021-07) Anderson, Nathaniel
    This thesis outlines the main design considerations of the sensor pod of a CubeSat-like, miniature re-entry vehicle, the Hypersonic Configurable Unit Ballistic Experiment (HyCUBE), that will serve as a versatile hypersonic flight test platform. HyCUBE's proposed first mission aims to collect experimental aerothermodynamic data of a hypersonic flight environment in order to investigate the chemical reactions that occur in that environment, namely the dissociation of nitrogen and oxygen. The data to be collected will contribute to the improvement and validation of computational models and ground testing methods. Numerical simulations were used to inform vehicle design decisions, using direct Simulation Monte Carlo (DSMC) method and computational fluid dynamics (CFD), when applicable and simplified estimation simulations when more appropriate. DSMC and CFD were utilized to establish the aerodynamic characteristics of the proposed vehicle, evaluate the heat-load such that the thermal protection system can be sized, and to produce three-dimensional flow solutions to guide sensor selection and placement. Simplified estimators solved the equations of motion to produce estimates for vehicle trajectories and used closed-form models to predict the aerothermodynamic environment at the vehicle stagnation point, which allowed for quick analysis of design changes. Preliminary designs for the HyCUBE vehicle form factor and sensor suite are proposed and discussed. The expected measurement environment was also used to optimize the placement of sensors to attempt maximize the amount of useful data that will be collected.
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    Numerical Analysis of the Diffusive Transport Phenomena in Hypersonic Flows
    (2023-07) Amato, Chiara
    One of the main focuses of hypersonic research is understanding the relevant physicochemical phenomena that characterize hypersonic flows. Shock-induced heating and strong thermochemical non-equilibrium are significant occurrences in high-enthalpy, high-speed flows. To accurately simulate such flows, one must ensure that the relevant effects are described in the physical model of the gas. In conventional CFD, we solve a set of governing equations, the Navier-Stokes equations, that include the terms related to viscous dissipation, heat transfer, and mass diffusion of multiple chemical species present in the flow. These diffusive processes are a continuum manifestation of transport processes at the molecular scale. According to kinetic theory, the Boltzmann equation fully describes the statistical behavior of dilute gas mixtures. A mathematical link between the Boltzmann and the Navier-Stokes equations provides a complete description of the transport phenomena with additional terms neglected in the conventional continuum flow representation. Thus, with this work, we study the effects of diffusion transport properties and chemical kinetics by simulating different hypersonic flows in the near-continuum regime. In particular, we compare the solutions obtained with US3D, a code routinely used for complex hypersonic computational fluid dynamics simulations, and MGDS, a code capable of large-scale 3D Direct Simulation Monte Carlo calculations. This work is part of a long-term effort to strike a balance between computational efficiency and accuracy in simulations and perform eventually coupled hybrid CFD-DSMC simulations of hypersonic flows.
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    Numerical Simulation Of Instabilities In Three-Dimensional Hypervelocity Boundary Layers
    (2020-03) Knutson, Anthony
    Direct numerical simulation has been used for decades to study the boundary layer transition process. The primary contributions of this dissertation are twofold. First, we identify barriers to performing accurate numerical simulation of instabilities using an existing finite-volume flow solver (US3D) and overcome these barriers by implementing improved numerical methods. In particular, we develop a new type of shock sensor that significantly reduces numerical noise and implement a time-accurate implicit method that significantly reduces numerical dissipation. Second, we perform numerical simulations of two different geometries - the boundary layer transition (BoLT) flight experiment geometry and a cone with a swept fin - to improve our understanding of instabilities in three-dimensional, high-speed boundary layers. We find a vortical mode and traveling crossflow are the dominant instabilities in the BoLT flowfield while a multi-modal instability in the horseshoe vortex leads to transition on the fin-cone geometry.