Macro Flashcards
What particle methods are used in Macroscopic scale?
Particle-in-cells
Vortex-in-cells
Smoothed Particle Hydrodynamics
How is the Particle-in-cell algorithm structured? (PIC)
1) realise the particle-state at time n
2) charge density evaluation on the grid
3) electrostatic potential evaluation on the grid
4) electrostatic field evaluation on the grid
5) final particle-state update
6) repeat to 1)
What are the typical applications of Particle-in-cell? (PIC)
collisionless plasma simulations
astrophysics simulations
What are the differences between Particle-in-cell and Cloud-in-cell? (PIC)
in Particle-in-cell, the charge of a particle is associated by its cell’s centroid
in Cloud-in-cell, the charge of a particle is determined by a weighting to the nearbiest cells’ centroids
How does the Particle-in-cell solves the complexity problem in simulating a large number of particles? (PIC)
1) consider a set of N particles randomly distributed over the domain A
2) the domain A is divided into finite subcells pf linear size delta
3) the size delta is determined in such a way that a sufficient number of particles is contained
How is the Hydrodynamics Particle-in-cell method’s algorithm structured? (PIC)
1) initiate the mean-field force based on the pressure gradient
2) define N particles and their states
3) evaluate the cell-quantities
4) computation of the momentum equation (Eulerian then Lagrangian)
5) update the particles’ velocities and energies
What are the differences between Particle-in-cell and Vortex-in-cell? (PIC)
VIC : vorticity-stream
PIC : pressure-velocity
VIC : lagrangian calculation first for the vorticity THEN eulerian to solve the stream fct and get the velocity field
PIC : eulerian computation first to solve for the pressure field THEN lagrangian for updating the velocities, energy, and motion
What is an important information of Particle-in-cell method?(PIC)
momentum is not conserved
What is a problem with Smoothed Particle Hydrodynamics? (SPH)
it has non-physical artifacts from molecular dynamics
What are the properties of kernel funcitons? (SPH)
radial symmetry
compact property
approximation of delta function
What is the Kernel fucntion? (SPH)
an interpolation function to determine how the properties of the neighbouring particles influence a given particle
When is Smoothed Particle Hydrodyanmics used? (SPH)
in CGI and astrophysics simulations
How is the Smoothed Particle Hydrodynamics algorithm structured? (SPH)
1) initialisation
2) realisation
3) partition domain into cells
4) construct cell linked lists
5) boundary condition
6) calculate new velocity
7) repeat to 2)
*similar to Molecular Dynamics or Direct Simulation Monte-Carlo but no average is needed
