Force bounds on x argument

src/ALE/Recon1d_PLM_CW.F90

@@ -168,15 +168,17 @@ real function f(this, k, x)
   class(PLM_CW), intent(in) :: this !< This reconstruction
   integer,       intent(in) :: k    !< Cell number
   real,          intent(in) :: x    !< Non-dimensional position within element [nondim]
+  real :: xc ! Bounded version of x [nondim]
   real :: du ! Difference across cell [A]
   real :: u_a, u_b ! Two estimate of f [A]
 
   du = this%ur(k) - this%ul(k)
+  xc = max( 0., min( 1., x ) )
 
   ! This expression for u_a can overshoot u_r but is good for x<<1
-  u_a = this%ul(k) + du * x
+  u_a = this%ul(k) + du * xc
   ! This expression for u_b can overshoot u_l but is good for 1-x<<1
-  u_b = this%ur(k) + du * ( x - 1. )
+  u_b = this%ur(k) + du * ( xc - 1. )
 
   ! Since u_a and u_b are both bounded, this will perserve uniformity
   f = 0.5 * ( u_a + u_b )

src/ALE/Recon1d_PPM_H4_2019.F90

@@ -119,6 +119,7 @@ real function f(this, k, x)
   class(PPM_H4_2019), intent(in) :: this !< This reconstruction
   integer,            intent(in) :: k    !< Cell number
   real,               intent(in) :: x    !< Non-dimensional position within element [nondim]
+  real :: xc ! Bounded version of x [nondim]
   real :: du ! Difference across cell [A]
   real :: a6 ! Collela and Woordward curvature parameter [A]
   real :: u_a, u_b ! Two estimate of f [A]
@@ -127,15 +128,16 @@ real function f(this, k, x)
 
   du = this%ur(k) - this%ul(k)
   a6 = 3.0 * ( ( this%u_mean(k) - this%ul(k) ) + ( this%u_mean(k) - this%ur(k) ) )
-  lmx = 1.0 - x
+  xc = max( 0., min( 1., x ) )
+  lmx = 1.0 - xc
 
   ! This expression for u_a can overshoot u_r but is good for x<<1
-  u_a = this%ul(k) + x * ( du + a6 * x )
+  u_a = this%ul(k) + xc * ( du + a6 * xc )
   ! This expression for u_b can overshoot u_l but is good for 1-x<<1
   u_b = this%ur(k) + lmx * ( - du + a6 * lmx )
 
   ! Since u_a and u_b are both side-bounded, using weights=0 or 1 will preserve uniformity
-  wb = 0.5 + sign(0.5, x - 0.5 ) ! = 1 @ x=0, = 0 @ x=1
+  wb = 0.5 + sign(0.5, xc - 0.5 ) ! = 1 @ x=0, = 0 @ x=1
   f = ( ( 1. - wb ) * u_a ) + ( wb * u_b )
 
 end function f
@@ -145,13 +147,15 @@ real function dfdx(this, k, x)
   class(PPM_H4_2019), intent(in) :: this !< This reconstruction
   integer,            intent(in) :: k    !< Cell number
   real,               intent(in) :: x    !< Non-dimensional position within element [nondim]
+  real :: xc ! Bounded version of x [nondim]
   real :: du ! Difference across cell [A]
   real :: a6 ! Collela and Woordward curvature parameter [A]
 
   du = this%ur(k) - this%ul(k)
   a6 = 3.0 * ( ( this%u_mean(k) - this%ul(k) ) + ( this%u_mean(k) - this%ur(k) ) )
+  xc = max( 0., min( 1., x ) )
 
-  dfdx = du + a6 * ( 2.0 * x - 1.0 )
+  dfdx = du + a6 * ( 2.0 * xc - 1.0 )
 
 end function dfdx