[SCM] Gerris Flow Solver branch, upstream, updated. b3aa46814a06c9cb2912790b23916ffb44f1f203

[Stephane Popinet]

The following commit has been merged in the upstream branch:
commit 3a2428beb64ced66936f222585b7b1667ba42073
Author: Stephane Popinet <popinet at users.sf.net>
Date:   Thu Aug 30 12:08:31 2007 +1000

    gradient_fine_coarse() uses only directly neighbouring cells
    
    Using a third cell in the opposite direction, although nominally second-order
    in space could cause instabilities. The reduced spatial order of this new
    implementation does not seem to affect the convergence rates for the test cases
    in the test suite.
    
    darcs-hash:20070830020831-d4795-b7e81854961665743c1b04bf61b15540872e7fea.gz

diff --git a/src/fluid.c b/src/fluid.c
index 16f8dbd..d83ba58 100644
--- a/src/fluid.c
+++ b/src/fluid.c
@@ -268,15 +268,10 @@ static gint perpendicular[FTT_NEIGHBORS][FTT_CELLS][2] =
    {{-1,-1},{-1,-1},{-1,-1},{-1,-1},{1,2},{0,2},{1,3},{0,3}}};
 #endif /* FTT_3D */
 
-static Gradient gradient_fine_coarse (const FttCellFace * face,
-				      guint v,
-				      gint max_level)
+static Gradient gradient_fine_coarse (const FttCellFace * face, guint v)
 {
   Gradient g;
-  guint level;
-  FttCell * n;
   GfsGradient p;
-  GfsSolidVector * s;
 #if (FTT_2D || FTT_2D3)
   gint dp;
 #else  /* FTT_3D */
@@ -286,12 +281,6 @@ static Gradient gradient_fine_coarse (const FttCellFace * face,
   g_assert (face != NULL);
   g_assert (ftt_face_type (face) == FTT_FINE_COARSE);
 
-  level = ftt_cell_level (face->cell);
-  s = GFS_STATE (face->cell)->solid;
-  n = (s != NULL && s->s[FTT_OPPOSITE_DIRECTION (face->d)] == 0.) ? NULL :
-    ftt_cell_neighbor (face->cell, FTT_OPPOSITE_DIRECTION (face->d));
-  g_assert (n == NULL || ftt_cell_level (n) == level);
-
   dp = perpendicular[face->d][FTT_CELL_ID (face->cell)];
 #if (FTT_2D || FTT_2D3)
   g_assert (dp >= 0);
@@ -301,34 +290,9 @@ static Gradient gradient_fine_coarse (const FttCellFace * face,
   p = interpolate_2D1 (face->neighbor, dp[0], dp[1], 1./4., 1./4., v);
 #endif /* FTT_3D */
 
-  if (n == NULL || GFS_IS_MIXED (n)) {
-    g.a = 2./3.;
-    g.b = 2.*p.a/3.;
-    g.c = 2.*p.b/3.;
-  }
-  else if (level == max_level || FTT_CELL_IS_LEAF (n)) {
-    g.a = 1./3.;
-    g.b = 8.*p.a/15.;
-    g.c = 8.*p.b/15. - GFS_VARIABLE (n, v)/5.;
-  }
-  else {
-    FttCellChildren children;
-    guint i, j;
-    gdouble sa = 0.;
-
-    j = ftt_cell_children_direction (n, face->d, &children);
-    g.a = 2./9.;
-    g.b = 14.*p.a/27.;
-    g.c = 0.;
-    for (i = 0; i < j; i++)
-      if (children.c[i]) {
-	gdouble w = GFS_IS_MIXED (children.c[i]) ? GFS_STATE (children.c[i])->solid->s[face->d] : 1.;
-	g.c += w*GFS_VARIABLE (children.c[i], v);
-	sa += w;
-      }
-    g_assert (sa > 0.);
-    g.c = (14.*p.b - 8.*g.c/sa)/27.;
-  }
+  g.a = 2./3.;
+  g.b = 2.*p.a/3.;
+  g.c = 2.*p.b/3.;
 
   return g;
 }
@@ -605,7 +569,7 @@ void gfs_face_gradient (const FttCellFace * face,
     /* neighbor is at a shallower level */
     Gradient gcf;
 
-    gcf = gradient_fine_coarse (face, v, max_level);
+    gcf = gradient_fine_coarse (face, v);
     g->a = gcf.a;
     g->b = gcf.b*GFS_VARIABLE (face->neighbor, v) + gcf.c;
   }
@@ -628,7 +592,7 @@ void gfs_face_gradient (const FttCellFace * face,
       for (i = 0; i < n; i++)
 	if ((f.cell = children.c[i])) {
 	  Gradient gcf;
-	  gcf = gradient_fine_coarse (&f, v, max_level);
+	  gcf = gradient_fine_coarse (&f, v);
 	  s = GFS_FACE_FRACTION (&f);
 	  g->a += s*gcf.b;
 	  g->b += s*(gcf.a*GFS_VARIABLE (f.cell, v) - gcf.c);
@@ -677,7 +641,7 @@ void gfs_face_weighted_gradient (const FttCellFace * face,
     Gradient gcf;
     gdouble w = GFS_STATE (face->cell)->f[face->d].v;
 
-    gcf = gradient_fine_coarse (face, v, max_level);
+    gcf = gradient_fine_coarse (face, v);
     g->a = w*gcf.a;
     g->b = w*(gcf.b*GFS_VARIABLE (face->neighbor, v) + gcf.c);
   }
@@ -703,7 +667,7 @@ void gfs_face_weighted_gradient (const FttCellFace * face,
 	  Gradient gcf;
 	  gdouble w = GFS_STATE (f.cell)->f[f.d].v;
 	
-	  gcf = gradient_fine_coarse (&f, v, max_level);
+	  gcf = gradient_fine_coarse (&f, v);
 	  g->a += w*gcf.b;
 	  g->b += w*(gcf.a*GFS_VARIABLE (f.cell, v) - gcf.c);
 	}
@@ -1155,10 +1119,10 @@ void gfs_face_gradient_flux (const FttCellFace * face,
     /* neighbor is at a shallower level */
     if (GFS_IS_MIXED (face->cell) || GFS_IS_MIXED (face->neighbor)) {
       if (!mixed_face_gradient (face, &gcf, v, max_level))
-	gcf = gradient_fine_coarse (face, v, max_level);
+	gcf = gradient_fine_coarse (face, v);
     }
     else
-      gcf = gradient_fine_coarse (face, v, max_level);
+      gcf = gradient_fine_coarse (face, v);
     g->a = w*gcf.a;
     g->b = w*(gcf.b*GFS_VARIABLE (face->neighbor, v) + gcf.c);
   }
@@ -1192,10 +1156,10 @@ void gfs_face_gradient_flux (const FttCellFace * face,
 	  w = GFS_STATE (f.cell)->f[f.d].v;
 	  if (GFS_IS_MIXED (f.cell) || GFS_IS_MIXED (f.neighbor)) {
 	    if (!mixed_face_gradient (&f, &gcf, v, max_level))
-	      gcf = gradient_fine_coarse (&f, v, max_level);
+	      gcf = gradient_fine_coarse (&f, v);
 	  }
 	  else
-	    gcf = gradient_fine_coarse (&f, v, max_level);
+	    gcf = gradient_fine_coarse (&f, v);
 	  g->a += w*gcf.b;
 	  g->b += w*(gcf.a*GFS_VARIABLE (f.cell, v) - gcf.c);
 	}

-- 
Gerris Flow Solver