Fixed an issue with the random Maxwellian subroutines

src/modules/common/moduleRandom.f90

@@ -48,24 +48,23 @@ MODULE moduleRandom
     END FUNCTION randomIntAB
 
     !Returns a random number in a Maxwellian distribution of mean 0 and width 1 with the Box-Muller Method
-    FUNCTION randomMaxwellian() RESULT(rnd)
-      USE moduleConstParam, ONLY: PI
-      IMPLICIT NONE
+    function randomMaxwellian() result(rnd)
+      USE moduleConstParam, only: pi
+      implicit none
 
-      REAL(8):: rnd
-      REAL(8):: v1, v2, Rsquare
+      real(8):: rnd
+      real(8):: v1, v2, Rsquare
 
-      Rsquare = 1.D0
-      do while (Rsquare >= 1.D0 .and. Rsquare > 0.D0)
-        v1 = 2.D0 * random() - 1.D0
-        v2 = 2.D0 * random() - 1.D0
-        Rsquare = v1**2 + v2**2
+      v1 = 0.d0
+      do while (v1 <= 0.d0)
+        v1 = random()
 
       end do
+      v2 = random()
 
-      rnd = v2 * sqrt(-2.D0 * log(Rsquare) / Rsquare)
+      rnd = sqrt(-2.d0*log(v1))*cos(2*pi*v2)
 
-    END FUNCTION randomMaxwellian
+    end function randomMaxwellian
 
     !Returns a random number in a Maxwellian distribution of mean 0 and width 1
     FUNCTION randomHalfMaxwellian() RESULT(rnd)

src/modules/moduleInject.f90

@@ -257,7 +257,7 @@ MODULE moduleInject
       CLASS(velDistGeneric), ALLOCATABLE, INTENT(out):: velDist
       REAL(8), INTENT(in):: temperature, m
 
-      velDist = velDistMaxwellian(vTh = DSQRT(temperature/m))
+      velDist = velDistMaxwellian(vTh = DSQRT(2.d0*temperature/m))
 
     END SUBROUTINE initVelDistMaxwellian
 
@@ -267,7 +267,7 @@ MODULE moduleInject
       CLASS(velDistGeneric), ALLOCATABLE, INTENT(out):: velDist
       REAL(8), INTENT(in):: temperature, m
 
-      velDist = velDistHalfMaxwellian(vTh = DSQRT(temperature/m))
+      velDist = velDistHalfMaxwellian(vTh = DSQRT(2.d0*temperature/m))
 
     END SUBROUTINE initVelDistHalfMaxwellian
 
@@ -289,7 +289,7 @@ MODULE moduleInject
       REAL(8):: v
       v = 0.D0
 
-      v = sqrt(2.0)*self%vTh*randomMaxwellian()
+      v = self%vTh*randomMaxwellian()/sqrt(2.d0)
 
     END FUNCTION randomVelMaxwellian
 
@@ -302,7 +302,7 @@ MODULE moduleInject
       REAL(8):: v
       v = 0.D0
 
-      v = sqrt(2.0)*self%vTh*randomHalfMaxwellian()
+      v = self%vTh*randomHalfMaxwellian()/sqrt(2.d0)
 
     END FUNCTION randomVelHalfMaxwellian
 
@@ -393,12 +393,6 @@ MODULE moduleInject
                                                      self%v(3)%obj%randomVel() /)
           end do
 
-          !If injecting a no-drift distribution and velocity is negative, reflect
-          if ((self%vMod == 0.D0) .and. &
-              (dot_product(direction, partInj(n)%v) < 0.D0)) then
-            partInj(n)%v = - partInj(n)%v
-
-          end if
 
           !Obtain natural coordinates of particle in cell
           partInj(n)%Xi = mesh%cells(partInj(n)%cell)%obj%phy2log(partInj(n)%r)