New and improved method to calculate collisions per iteration:

In each iteration, number of collisions are calculate as a REAL variable
(collFrac) and stored in each cell. The number of collisions is
calculated as FLOOR(collFrac) and, if it is >1 collisions are computed
as usual. Per each collision calculated, 1.0 is removed from collFrac

src/modules/mesh/moduleMesh.f90

@@ -134,6 +134,8 @@ MODULE moduleMesh
     INTEGER(KIND=OMP_LOCK_KIND):: lock
     !Number of collisions per volume
     INTEGER:: nColl = 0
+    !Collisional fraction
+    REAL(8):: collFrac = 0.D0
     !Total weight of particles inside cell
     REAL(8):: totalWeight = 0.D0
     CONTAINS
@@ -379,7 +381,7 @@ MODULE moduleMesh
     END SUBROUTINE findCell
 
     !Computes collisions in element
-    SUBROUTINE collision(self, t)
+    SUBROUTINE collision(self)
       USE moduleCollisions
       USE moduleSpecies
       USE moduleList
@@ -388,7 +390,6 @@ MODULE moduleMesh
       IMPLICIT NONE
 
       CLASS(meshVol), INTENT(inout):: self
-      INTEGER, INTENT(in):: t
       INTEGER:: modCollisions !Remain of current iteration and everyCollisions
       INTEGER:: iterToCollisions !Number of iterations from current to next collision
       INTEGER:: nPart !Number of particles inside the cell
@@ -401,36 +402,25 @@ MODULE moduleMesh
       REAL(8):: sigmaVrelMaxNew
       TYPE(pointerArray), ALLOCATABLE:: partTemp(:)
 
-      modCollisions = MOD(t, everyCollisions)
-      iterToCollisions = everyCollisions - modCollisions
-
       nPart = self%listPart_in%amount
+      !Computes iterations if there is more than one particle in the cell
       IF (nPart > 1) THEN
-        IF (modCollisions == 0) THEN
-          !Collisional iteration, computes the number of iterations
-          pMax = self%totalWeight*self%sigmaVrelMax*tauCollisions/self%volume
-          self%nColl = INT(REAL(nPart)*pMax*0.5D0)
+        !Probability of collision
+        pMax = self%totalWeight*self%sigmaVrelMax*tauMin/self%volume
 
-        END IF
+        !Increases the collisional fraction of the cell
+        self%collFrac = self%collFrac + REAL(nPart)*pMax*0.5D0
+        
+        !Number of collisions in the cell
+        self%nColl = FLOOR(self%collFrac)
 
-        IF (self%nColl > iterToCollisions) THEN
-          nCollIter = self%nColl / iterToCollisions
-
-        ELSE
-          nCollIter = self%nColl
-
-        END IF
-
-        IF (nCollIter > 0) THEN
+        IF (self%nColl > 0) THEN
           !Converts the list of particles to an array for easy access
           partTemp = self%listPart_in%convert2Array()
 
-          !Removes collisions from this iteration form the total in the cell
-          self%nColl = self%nColl - nCollIter
-
         END IF
 
-        DO n = 1, nCollIter
+        DO n = 1, self%nColl
           !Select random numbers
           rnd = random(1, nPart)
           part_i => partTemp(rnd)%part
@@ -448,8 +438,12 @@ MODULE moduleMesh
             self%sigmaVrelMax = sigmaVrelMaxNew
 
           END IF
+
+          !Removes one collision from the collisional fraction
+          self%collFrac = self%collFrac - 1.D0
             
         END DO
+
       END IF
 
     END SUBROUTINE collision
@@ -552,7 +546,7 @@ MODULE moduleMesh
       CHARACTER (LEN=iterationDigits):: tstring
 
 
-      IF (collOutput .AND. MOD(t, everyCollisions) == 0) THEN
+      IF (collOutput) THEN
         time = DBLE(t)*tauMin*ti_ref
         WRITE(tstring, iterationFormat) t