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First conservative implementation of Coulomb

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I am doing a trick in which I ensure that energy is conserved for
Coulomb collisions. This was not happening and what an issue for
different mass ratios. Still, this can cause an issue on getting the
right relaxation rates, still necessary to check it.
This commit is contained in:
Jorge Gonzalez 2023-03-08 16:37:45 +01:00
commit fe94615a27
4 changed files with 26 additions and 13 deletions
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29
src/modules/mesh/moduleMesh.f90
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@ -975,10 +975,11 @@ MODULE moduleMesh
REAL(8):: delta_par, delta_par_square, delta_per, delta_per_square
REAL(8):: W(3), dW(2), normW !Relative velocity between particle and species and its increment
REAL(8):: l2, l, lW, AW
REAL(8):: deltaV(1:3), totalDeltaV_ij, normDeltaV
REAL(8):: rnd
!$OMP SINGLE
!$OMP DO SCHEDULE(DYNAMIC) PRIVATE(partTemp)
DO e = 1, self%numCells
cell => self%cells(e)%obj
cellNodes = cell%getNodes(cell%nNodes)
@ -1003,6 +1004,7 @@ MODULE moduleMesh
END DO
!Loop over particles of species_i
totalDeltaV_ij = 0.D0
partTemp => cell%listPart_in(i)%head
DO WHILE(ASSOCIATED(partTemp))
density = cell%gatherF(partTemp%part%Xi, cell%nNodes, densityNodes)
@ -1036,16 +1038,18 @@ MODULE moduleMesh
e2(3) = 0.D0
e2 = normalize(e2)
!Third one is perpendicular to the other two
e3 = crossProduct(e2, e1)
e3 = crossProduct(e1, e2)
e3 = normalize(e3)
!Random number for direction
rnd = PI2*random()
!Change particle velocity
partTemp%part%v = partTemp%part%v + dW(1)*e1 + dW(2)*(COS(rnd)*e2 + &
SIN(rnd)*e3)
deltaV = dW(1)*e1 + dW(2)*(COS(rnd)*e2 + SIN(rnd)*e3)
totalDeltaV_ij = totalDeltaV_ij + NORM2(deltaV)
!Change particle velocity
partTemp%part%v = partTemp%part%v + deltaV
partTemp => partTemp%next
END DO
@ -1062,6 +1066,8 @@ MODULE moduleMesh
END DO
!Divide total momentum exchanged among all the particles of species j
normDeltaV = totalDeltaV_ij / REAL(cell%listPart_in(j)%amount) * (self%sp_i%weight*self%sp_i%m)/(self%sp_j%weight*self%sp_j%m)
!Loop over particles of species_j
partTemp => cell%listPart_in(j)%head
DO WHILE(ASSOCIATED(partTemp))
@ -1086,6 +1092,10 @@ MODULE moduleMesh
dW(1) = delta_par*tauMin + randomMaxwellian()*SQRT(delta_par_square*tauMin)
dW(2) = ABS(randomMaxwellian()*SQRT(delta_per_square*tauMin))
!Normalize with average exchange per particle
!TODO: This is a dirty trick, it should not be neccessary but I don't lnow why it is.
dW = normDeltaV*dW/NORM2(dW)
!System of reference for the velocity change
!First one is parallel to the relative velocity
e1 = normalize(W)
@ -1095,15 +1105,16 @@ MODULE moduleMesh
e2(3) = 0.D0
e2 = normalize(e2)
!Third one is perpendicular to the other two
e3 = crossProduct(e2, e1)
e3 = crossProduct(e1, e2)
e3 = normalize(e3)
!Random number for direction
rnd = PI2*random()
deltaV = dW(1)*e1 + dW(2)*(COS(rnd)*e2 + SIN(rnd)*e3)
!Change particle velocity
partTemp%part%v = partTemp%part%v + dW(1)*e1 + dW(2)*(COS(rnd)*e2 + &
SIN(rnd)*e3)
partTemp%part%v = partTemp%part%v + deltaV
partTemp => partTemp%next
@ -1114,7 +1125,7 @@ MODULE moduleMesh
END DO
END DO
!$OMP END SINGLE
!$OMP END DO
END SUBROUTINE doCoulomb