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! Copyright 2019 Maxence Thevenet, Weiqun Zhang
!
! This file is part of WarpX.
!
! License: BSD-3-Clause-LBNL
module warpx_ES_push_particles
use iso_c_binding
use amrex_fort_module, only : amrex_real, amrex_particle_real
implicit none
contains
!
! This routine updates the particle positions and velocities using the
! leapfrog time integration algorithm, given the electric fields at the
! particle positions. It also enforces specular reflection off the domain
! walls.
!
! Arguments:
! particles : a pointer to the particle array-of-structs
! ns : the stride length of particle struct (the size of the struct in number of reals)
! np : the number of particles
! vx_p : the particle x-velocities
! vy_p : the particle y-velocities
! vz_p : the particle z-velocities
! Ex_p : the electric field in the x-direction at the particle positions
! Ey_p : the electric field in the y-direction at the particle positions
! Ez_p : the electric field in the z-direction at the particle positions
! charge : the charge of this particle species
! mass : the mass of this particle species
! dt : the time step
! prob_lo : the left-hand corner of the problem domain
! prob_hi : the right-hand corner of the problem domain
!
subroutine warpx_push_leapfrog_3d(particles, ns, np, &
vx_p, vy_p, vz_p, &
Ex_p, Ey_p, Ez_p, &
charge, mass, dt, &
prob_lo, prob_hi) &
bind(c,name='warpx_push_leapfrog_3d')
integer, value, intent(in) :: ns, np
real(amrex_particle_real), intent(inout) :: particles(ns,np)
real(amrex_particle_real), intent(inout) :: vx_p(np), vy_p(np), vz_p(np)
real(amrex_real), intent(in) :: Ex_p(np), Ey_p(np), Ez_p(np)
real(amrex_real), intent(in) :: charge
real(amrex_real), intent(in) :: mass
real(amrex_real), intent(in) :: dt
real(amrex_real), intent(in) :: prob_lo(3), prob_hi(3)
integer n
real(amrex_real) fac
fac = charge * dt / mass
do n = 1, np
vx_p(n) = vx_p(n) + fac * Ex_p(n)
vy_p(n) = vy_p(n) + fac * Ey_p(n)
vz_p(n) = vz_p(n) + fac * Ez_p(n)
particles(1, n) = particles(1, n) + dt * vx_p(n)
particles(2, n) = particles(2, n) + dt * vy_p(n)
particles(3, n) = particles(3, n) + dt * vz_p(n)
! bounce off the walls in the x...
do while (particles(1, n) .lt. prob_lo(1) .or. particles(1, n) .gt. prob_hi(1))
if (particles(1, n) .lt. prob_lo(1)) then
particles(1, n) = 2.d0*prob_lo(1) - particles(1, n)
else
particles(1, n) = 2.d0*prob_hi(1) - particles(1, n)
end if
vx_p(n) = -vx_p(n)
end do
! ... y...
do while (particles(2, n) .lt. prob_lo(2) .or. particles(2, n) .gt. prob_hi(2))
if (particles(2, n) .lt. prob_lo(2)) then
particles(2, n) = 2.d0*prob_lo(2) - particles(2, n)
else
particles(2, n) = 2.d0*prob_hi(2) - particles(2, n)
end if
vy_p(n) = -vy_p(n)
end do
! ... and z directions
do while (particles(3, n) .lt. prob_lo(3) .or. particles(3, n) .gt. prob_hi(3))
if (particles(3, n) .lt. prob_lo(3)) then
particles(3, n) = 2.d0*prob_lo(3) - particles(3, n)
else
particles(3, n) = 2.d0*prob_hi(3) - particles(3, n)
end if
vz_p(n) = -vz_p(n)
end do
end do
end subroutine warpx_push_leapfrog_3d
subroutine warpx_push_leapfrog_2d(particles, ns, np, &
vx_p, vy_p, &
Ex_p, Ey_p, &
charge, mass, dt, &
prob_lo, prob_hi) &
bind(c,name='warpx_push_leapfrog_2d')
integer, value, intent(in) :: ns, np
real(amrex_particle_real), intent(inout) :: particles(ns,np)
real(amrex_particle_real), intent(inout) :: vx_p(np), vy_p(np)
real(amrex_real), intent(in) :: Ex_p(np), Ey_p(np)
real(amrex_real), intent(in) :: charge
real(amrex_real), intent(in) :: mass
real(amrex_real), intent(in) :: dt
real(amrex_real), intent(in) :: prob_lo(2), prob_hi(2)
integer n
real(amrex_real) fac
fac = charge * dt / mass
do n = 1, np
vx_p(n) = vx_p(n) + fac * Ex_p(n)
vy_p(n) = vy_p(n) + fac * Ey_p(n)
particles(1, n) = particles(1, n) + dt * vx_p(n)
particles(2, n) = particles(2, n) + dt * vy_p(n)
! bounce off the walls in the x...
do while (particles(1, n) .lt. prob_lo(1) .or. particles(1, n) .gt. prob_hi(1))
if (particles(1, n) .lt. prob_lo(1)) then
particles(1, n) = 2.d0*prob_lo(1) - particles(1, n)
else
particles(1, n) = 2.d0*prob_hi(1) - particles(1, n)
end if
vx_p(n) = -vx_p(n)
end do
! ... y...
do while (particles(2, n) .lt. prob_lo(2) .or. particles(2, n) .gt. prob_hi(2))
if (particles(2, n) .lt. prob_lo(2)) then
particles(2, n) = 2.d0*prob_lo(2) - particles(2, n)
else
particles(2, n) = 2.d0*prob_hi(2) - particles(2, n)
end if
vy_p(n) = -vy_p(n)
end do
end do
end subroutine warpx_push_leapfrog_2d
end module warpx_ES_push_particles
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