Adding explanation

cpinte · Nov 21, 2023 · 066beeb · 066beeb
1 parent 31d5cde
commit 066beeb
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diff --git a/src/cylindrical_grid.f90 b/src/cylindrical_grid.f90
@@ -1201,6 +1201,20 @@ real(dp) function distance_to_closest_wall_cyl(id,icell,x,y,z) result(s)
 
     if (l3D) then
        ! phi walls
+       !
+       ! Distance between a line with equation a*x+by+c=0, ie y=-a/b*x-c/b and point (x0,y0) is:
+       !
+       ! d = |a*x0+b*y0+c|/sqrt(a**2+b**2)
+       !
+       ! In case of phi walls, we have y = x * tan(phi) so:
+       !
+       ! a = -sin(phi)
+       ! b = cos(phi)
+       ! c = 0
+       !
+       ! and therefore
+       !
+       ! d = |x0*sin(phi) - y0*cos(theta)| / sqrt[cos^2 + sin^2]
        s5 = abs(x*sin_phi_lim(k0) - y*cos_phi_lim(k0))
        s6 = abs(x*sin_phi_lim(k0-1) - y*cos_phi_lim(k0-1))
        s = min(s1,s2,s3,s4,s5,s6)

diff --git a/src/spherical_grid.f90 b/src/spherical_grid.f90
@@ -466,13 +466,27 @@ real(dp) function distance_to_closest_wall_sph(id,icell,x,y,z) result(s)
     s1 = r_lim(ri0) - r
     s2 = r - r_lim(ri0-1)
 
-    ! theta walls
+    ! theta walls (same method as phi)
     z0 = abs(z)
     s3 = abs(rcyl*w_lim(thetaj0) - z0*cos_phi_lim(thetaj0))
     s4 = abs(rcyl*w_lim(thetaj0-1) - z0*cos_phi_lim(thetaj0-1))
 
     if (l3D) then
        ! phi walls
+       !
+       ! Distance between a line with equation a*x+by+c=0, ie y=-a/b*x-c/b and point (x0,y0) is:
+       !
+       ! d = |a*x0+b*y0+c|/sqrt(a**2+b**2)
+       !
+       ! In case of phi walls, we have y = x * tan(phi) so:
+       !
+       ! a = -sin(phi)
+       ! b = cos(phi)
+       ! c = 0
+       !
+       ! and therefore
+       !
+       ! d = |x0*sin(phi) - y0*cos(theta)| / sqrt[cos^2 + sin^2]
        s5 = abs(x*sin_phi_lim(k0) - y*cos_phi_lim(k0))
        s6 = abs(x*sin_phi_lim(k0-1) - y*cos_phi_lim(k0-1))
        s = min(s1,s2,s3,s4,s5,s6)