Regular sensitivity computation avoiding chaotic effects in particle-in-cell plasma methods
[1];
- Univ. of Illinois at Urbana-Champaign, Urbana, IL (United States). Dept. of Mechanical Science and Engineering
- Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Center for Computing Research
- Univ. of Illinois at Urbana-Champaign, Urbana, IL (United States). Dept. of Mechanical Science and Engineering and Dept. of Aerospace Engineering
Particle-in-cell (PIC) simulation methods are attractive for representing species distribution functions in plasmas. However, as a model, they introduce uncertain parameters, and for quantifying their prediction uncertainty it is useful to be able to assess the sensitivity of a quantity-of-interest (QoI) to these parameters. Such sensitivity information is likewise useful for optimization. However, computing sensitivity for PIC methods is challenging due to the chaotic particle dynamics, and sensitivity techniques remain underdeveloped compared to those for Eulerian discretizations. This challenge is examined from a dual particle–continuum perspective that motivates a new sensitivity discretization. Two routes to sensitivity computation are presented and compared: a direct fully-Lagrangian particle-exact approach provides sensitivities of each particle trajectory, and a new particle-pdf discretization, which is formulated from a continuum perspective but discretized by particles to take the advantages of the same type of Lagrangian particle description leveraged by PIC methods. Since the sensitivity particles in this approach are only indirectly linked to the plasma-PIC particles, they can be positioned and weighted independently for efficiency and accuracy. The corresponding numerical algorithms are presented here in mathematical detail. The advantage of the particle-pdf approach in avoiding the spurious chaotic sensitivity of the particle-exact approach is demonstrated for Debye shielding and sheath configurations. In essence, the continuum perspective makes implicit the distinctness of the particles, which circumvents the Lyapunov instability of the N-body PIC system. The cost of the particle-pdf approach is comparable to the baseline PIC simulation.
- Research Organization:
- Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
- Sponsoring Organization:
- USDOE National Nuclear Security Administration (NNSA)
- Grant/Contract Number:
- AC04-94AL85000; NA0002374; NA0003525
- OSTI ID:
- 1570259
- Alternate ID(s):
- OSTI ID: 1703198
- Report Number(s):
- SAND2019-10797J; 679339; TRN: US2001260
- Journal Information:
- Journal of Computational Physics, Vol. 400, Issue C; ISSN 0021-9991
- Publisher:
- ElsevierCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
Similar Records
Fluid-Kinetic Coupling: Advanced Discretizations for Simulations on Emerging Heterogeneous Architectures (LDRD FY20-0643)
Comparison of Conservation Behavior in Several Variationally Derived Implementations for Simulating Electromagnetic Plasmas