Nonlinear evolution of Vlasov equilibria

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1989

OSTI ID:5906900

Demeio, L

In this work, the author investigates numerically the evolution of perturbed Vlasov equilibria, according to the full nonlinear system, with particular emphasis on analyzing the asymptotic states towards which the system evolves. The simulations are carried out with the numerical code that has been implemented on the Cray X-MP of the Pittsburgh Supercomputing Center and which is based on the splitting scheme algorithm. Maxwellian, symmetric and one sided bump-on tail and two-stream type of equilibrium distributions are considered: the only distribution which seems to evolve towards a BGK equilibrium is the two-stream while the asymptotic states for all the other distributions are better described by superpositions of possible BGK modes. Perturbations with wave-like dependence in space and both symmetric and non-symmetric dependence on velocity are considered. For weakly unstable modes, the problem of the discrepancy between different theoretical models about the scaling of the saturation amplitude with the growth rate is addressed, for the first time with the splitting scheme algorithm. The results are in agreement with the ones obtained in the past with less accurate algorithms and do not exhibit spurious numerical effect present in those. Finally, collisions are included in the splitting scheme, in the form of the Krook model, and some simulations are performed, whose results are in agreement with existing theoretical models.

• Research Organization: Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (USA)
• OSTI ID: 5906900
• Country of Publication: United States
• Language: English

Related Subjects

657000* -- Theoretical & Mathematical Physics
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ALGORITHMS
BOLTZMANN-VLASOV EQUATION
COMPUTERIZED SIMULATION
COMPUTERS
CRAY COMPUTERS
DIFFERENTIAL EQUATIONS
DIGITAL COMPUTERS
EQUATIONS
FLUCTUATIONS
MATHEMATICAL LOGIC
NONLINEAR PROBLEMS
NUMERICAL SOLUTION
PARTIAL DIFFERENTIAL EQUATIONS
SIMULATION
SUPERCOMPUTERS
VARIATIONS