Geometric slow manifold, interconnected, and adjoint sensitivity methods for modeling and design of high-contrast plasma systems
Abstract
Rapid exploration of design space is enabled by simulation driven optimal design and control methods. This requires accurately predicting the plasma response as well as the adjoint sensitivity to optimize the thruster geometries (16). Therefore, an essential component of our research program will be to develop computationally inexpensive and accurate simulations for high-contrast plasma physics problems. Our two-pronged strategy for meeting this challenge will exploit the Hamiltonian structure in order to (a) identify continuum reduced models that inherit structural properties such as energy, momentum, and wave-action conservation laws, and (b) directly build fully-discrete models that are able to accurately resolve the dynamics of highcontrast observables. We will perform adjoint sensitivity analysis for our reduced models using the fact that any system of differential equations and its adjoint equations are described by a formal Lagrangian (24; 25). Variational integrators can be used to efficiently compute adjoints, which arise in sensitivity analysis (12; 13), adaptive mesh refinement (32), uncertainty quantification (57), automatic differentiation (18), superconvergent functional recovery (45), optimal control (48), optimal design (16), and optimal estimation (42). Transition to turbulence in high-speed flight- Incoming disturbances and particulates At high speeds, flight vehicles experience extreme aero-thermal loads when the flow transitions from a laminar to a turbulent state, either due to incoming disturbances or particles. Free-stream disturbances can modify and be modified by the leading-edge shock of the flight vehicle; Downstream, the boundary layer is only receptive to the a portion of the disturbance spectrum, and the impact of the flow stability depends on the amount of energy contained in these modes. Provided sufficient energy is present in the unstable frequency band, the boundary layer can be destabilized and break down to turbulence. Particles, on the other hand, are imparted with a sudden acceleration as they traverse the leading-edge shock of the flight article, and their trajectories are deflected as they approach the flight article. If the particles are sufficiently small, they respond to the flow between the shock and the vehicle and behave as tracers that avoid impact with the surface. The larger particles will enter the boundary layer, potentially impact the surface, and generate wave packets that spread as they propagate downstream. Existing efforts are aimed at characterizing the flight environment, both in terms of measuring the disturbance fields and particulates, followed by evaluating the potential impact of such disturbances. This effort adopts an alternative view.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 29, 2024
- Source ID
- FA95502310279
Entities
People
- Melvin Leok
Organizations
- Air Force Office of Scientific Research
- United States Air Force
- University of California, San Diego