/*
Philippose Rajan - 11 June 2009
Added an initial experimental function for
generating prismatic boundary layers on
a given set of surfaces.
The number of layers, height of the first layer
and the growth / shrink factor can be specified
by the user
Currently, the layer height is calculated using:
height = h_first_layer * (growth_factor^(num_layers - 1))
*/
void GenerateBoundaryLayer (Mesh & mesh, MeshingParameters & mp)
{
int i, j;
ofstream dbg("BndLayerDebug.log");
// Angle between a surface element and a growth-vector below which
// a prism is project onto that surface as a quad
// (in degrees)
double angleThreshold = 5.0;
cout << "Generate Prismatic Boundary Layers (Experimental)...." << endl;
// Use an array to support creation of boundary
// layers for multiple surfaces in the future...
Array<int> surfid;
int surfinp = 0;
int prismlayers = 1;
double hfirst = 0.01;
double growthfactor = 1.0;
// Monitor and print out the number of prism and quad elements
// added to the mesh
int numprisms = 0;
int numquads = 0;
while(surfinp >= 0)
{
cout << "Enter Surface ID (-1 to end list): ";
cin >> surfinp;
if(surfinp >= 0) surfid.Append(surfinp);
}
cout << "Number of surfaces entered = " << surfid.Size() << endl;
cout << "Selected surfaces are:" << endl;
for(i = 1; i <= surfid.Size(); i++)
{
cout << "Surface " << i << ": " << surfid.Elem(i) << endl;
}
cout << endl << "Enter number of prism layers: ";
cin >> prismlayers;
if(prismlayers < 1) prismlayers = 1;
cout << "Enter height of first layer: ";
cin >> hfirst;
if(hfirst <= 0.0) hfirst = 0.01;
cout << "Enter layer growth / shrink factor: ";
cin >> growthfactor;
if(growthfactor <= 0.0) growthfactor = 0.5;
cout << "Old NP: " << mesh.GetNP() << endl;
cout << "Old NSE: " << mesh.GetNSE() << endl;
for(int layer = prismlayers; layer >= 1; layer--)
{
cout << "Generating layer: " << layer << endl;
const MeshTopology& meshtopo = mesh.GetTopology();
const_cast<MeshTopology &> (meshtopo).SetBuildEdges(true);
const_cast<MeshTopology &> (meshtopo).SetBuildFaces(true);
const_cast<MeshTopology &> (meshtopo).Update();
double layerht = hfirst;
if(growthfactor == 1)
{
layerht = layer * hfirst;
}
else
{
layerht = hfirst*(pow(growthfactor,(layer+1)) - 1)/(growthfactor - 1);
}
cout << "Layer Height = " << layerht << endl;
// Need to store the old number of points and
// surface elements because there are new points and
// surface elements being added during the process
int np = mesh.GetNP();
int nse = mesh.GetNSE();
// Safety measure to ensure no issues with mesh
// consistency
int nseg = mesh.GetNSeg();
// Indicate which points need to be remapped
BitArray bndnodes(np);
// Map of the old points to the new points
Array<int> mapto(np);
// Growth vectors for the prismatic layer based on
// the effective surface normal at a given point
Array<Vec3d> growthvectors(np);
// Bit array to identify all the points belonging
// to the surface of interest
bndnodes.Clear();
// Run through all the surface elements and mark the points
// belonging to those where a boundary layer has to be created.
// In addition, also calculate the effective surface normal
// vectors at each of those points to determine the mesh motion
// direction
cout << "Marking points for remapping...." << endl;
for (i = 1; i <= nse; i++)
{
int snr = mesh.SurfaceElement(i).GetIndex();
// cout << "snr = " << snr << endl;
if (surfid.Contains(snr))
{
Element2d & sel = mesh.SurfaceElement(i);
int selNP = sel.GetNP();
for(j = 1; j <= selNP; j++)
{
// Set the bitarray to indicate that the
// point is part of the required set
bndnodes.Set(sel.PNum(j));
// Vec3d& surfacenormal = Vec3d(); ????
Vec3d surfacenormal;
// Calculate the surface normal at the current point
// with respect to the current surface element
GetSurfaceNormal(mesh,sel,j,surfacenormal);
// Add the surface normal to the already existent one
// (This gives the effective normal direction at corners
// and curved areas)
growthvectors.Elem(sel.PNum(j)) = growthvectors.Elem(sel.PNum(j))
+ surfacenormal;
}
}
}
// Add additional points into the mesh structure in order to
// clone the surface elements.
// Also invert the growth vectors so that they point inwards,
// and normalize them
cout << "Cloning points and calculating growth vectors...." << endl;
for (i = 1; i <= np; i++)
{
if (bndnodes.Test(i))
{
mapto.Elem(i) = mesh.AddPoint (mesh.Point (i));
growthvectors.Elem(i).Normalize();
growthvectors.Elem(i) *= -1.0;
}
else
{
mapto.Elem(i) = 0;
growthvectors.Elem(i) = Vec3d(0,0,0);
}
}
// Add quad surface elements at edges for surfaces which
// dont have boundary layers
// Bit array to keep track of segments already processed
BitArray segsel(nseg);
// Set them all to "1" to initially activate all segments
segsel.Set();
cout << "Adding 2D Quad elements on required surfaces...." << endl;
for (i = 1; i <= nseg; i++)
{
int seg_p1 = mesh.LineSegment(i)[0];
int seg_p2 = mesh.LineSegment(i)[1];
// Only go in if the segment is still active, and if both its
// surface index is part of the "hit-list"
if(segsel.Test(i) && surfid.Contains(mesh.LineSegment(i).si))
{
// clear the bit to indicate that this segment has been processed
segsel.Clear(i);
// Find matching segment pair on other surface
for(j = 1; j <= nseg; j++)
{
int segpair_p1 = mesh.LineSegment(j)[1];
int segpair_p2 = mesh.LineSegment(j)[0];
// Find the segment pair on the neighbouring surface element
// Identified by: seg1[0] = seg_pair[1] and seg1[1] = seg_pair[0]
if(segsel.Test(j) && ((segpair_p1 == seg_p1) && (segpair_p2 == seg_p2)))
{
// clear bit to indicate that processing of this segment is done
segsel.Clear(j);
// Only worry about those surfaces which are not in the
// boundary layer list
if(!surfid.Contains(mesh.LineSegment(j).si))
{
int pnt_commelem = 0;
int pnum_commelem = 0;
Array<int> pnt1_elems;
Array<int> pnt2_elems;
meshtopo.GetVertexSurfaceElements(segpair_p1,pnt1_elems);
meshtopo.GetVertexSurfaceElements(segpair_p2,pnt2_elems);
for(int k = 1; k <= pnt1_elems.Size(); k++)
{
Element2d pnt1_sel = mesh.SurfaceElement(pnt1_elems.Elem(k));
for(int l = 1; l <= pnt2_elems.Size(); l++)
{
Element2d pnt2_sel = mesh.SurfaceElement(pnt2_elems.Elem(l));
if((pnt1_sel.GetIndex() == mesh.LineSegment(j).si)
&& (pnt2_sel.GetIndex() == mesh.LineSegment(j).si)
&& (pnt1_elems.Elem(k) == pnt2_elems.Elem(l)))
{
pnt_commelem = pnt1_elems.Elem(k);
}
}
}
for(int k = 1; k <= mesh.SurfaceElement(pnt_commelem).GetNP(); k++)
{
if((mesh.SurfaceElement(pnt_commelem).PNum(k) != segpair_p1)
&& (mesh.SurfaceElement(pnt_commelem).PNum(k) != segpair_p2))
{
pnum_commelem = mesh.SurfaceElement(pnt_commelem).PNum(k);
}
}
Vec3d surfelem_vect, surfelem_vect1;
Element2d & commsel = mesh.SurfaceElement(pnt_commelem);
dbg << "NP= " << commsel.GetNP() << " : ";
for(int k = 1; k <= commsel.GetNP(); k++)
{
GetSurfaceNormal(mesh,commsel,k,surfelem_vect1);
surfelem_vect += surfelem_vect1;
}
surfelem_vect.Normalize();
double surfangle = Angle(growthvectors.Elem(segpair_p1),surfelem_vect);
dbg << "V1= " << surfelem_vect1
<< " : V2= " << surfelem_vect1
<< " : V= " << surfelem_vect
<< " : GV= " << growthvectors.Elem(segpair_p1)
<< " : Angle= " << surfangle * 180 / 3.141592;
// remap the segments to the new points
mesh.LineSegment(i)[0] = mapto.Get(seg_p1);
mesh.LineSegment(i)[1] = mapto.Get(seg_p2);
mesh.LineSegment(j)[1] = mapto.Get(seg_p1);
mesh.LineSegment(j)[0] = mapto.Get(seg_p2);
if((surfangle < (90 + angleThreshold) * 3.141592 / 180.0)
&& (surfangle > (90 - angleThreshold) * 3.141592 / 180.0))
{
dbg << " : quad\n";
// Since the surface is lower than the threshold, change the effective
// prism growth vector to match with the surface vector, so that
// the Quad which is created lies on the original surface
//growthvectors.Elem(segpair_p1) = surfelem_vect;
// Add a quad element to account for the prism volume
// element which is going to be added
Element2d sel(QUAD);
sel.PNum(4) = mapto.Get(seg_p1);
sel.PNum(3) = mapto.Get(seg_p2);
sel.PNum(2) = segpair_p2;
sel.PNum(1) = segpair_p1;
sel.SetIndex(mesh.LineSegment(j).si);
mesh.AddSurfaceElement(sel);
numquads++;
}
else
{
dbg << "\n";
for (int k = 1; k <= pnt1_elems.Size(); k++)
{
Element2d & pnt_sel = mesh.SurfaceElement(pnt1_elems.Elem(k));
if(pnt_sel.GetIndex() == mesh.LineSegment(j).si)
{
for(int l = 1; l <= pnt_sel.GetNP(); l++)
{
if(pnt_sel.PNum(l) == segpair_p1)
{
pnt_sel.PNum(l) = mapto.Get(seg_p1);
}
else if(pnt_sel.PNum(l) == segpair_p2)
{
pnt_sel.PNum(l) = mapto.Get(seg_p2);
}
}
}
}
for (int k = 1; k <= pnt2_elems.Size(); k++)
{
Element2d & pnt_sel = mesh.SurfaceElement(pnt2_elems.Elem(k));
if(pnt_sel.GetIndex() == mesh.LineSegment(j).si)
{
for(int l = 1; l <= pnt_sel.GetNP(); l++)
{
if(pnt_sel.PNum(l) == segpair_p1)
{
pnt_sel.PNum(l) = mapto.Get(seg_p1);
}
else if(pnt_sel.PNum(l) == segpair_p2)
{
pnt_sel.PNum(l) = mapto.Get(seg_p2);
}
}
}
}
}
}
else
{
// If the code comes here, it indicates that we are at
// a line segment pair which is at the intersection
// of two surfaces, both of which have to grow boundary
// layers.... here too, remapping the segments to the
// new points is required
mesh.LineSegment(i)[0] = mapto.Get(seg_p1);
mesh.LineSegment(i)[1] = mapto.Get(seg_p2);
mesh.LineSegment(j)[1] = mapto.Get(seg_p1);
mesh.LineSegment(j)[0] = mapto.Get(seg_p2);
}
}
}
}
}
// Add prismatic cells at the boundaries
cout << "Generating prism boundary layer volume elements...." << endl;
for (i = 1; i <= nse; i++)
{
Element2d & sel = mesh.SurfaceElement(i);
if(surfid.Contains(sel.GetIndex()))
{
Element el(PRISM);
for (j = 1; j <= sel.GetNP(); j++)
{
// Check (Doublecheck) if the corresponding point has a
// copy available for remapping
if (mapto.Get(sel.PNum(j)))
{
// Define the points of the newly added Prism cell
el.PNum(j+3) = mapto.Get(sel.PNum(j));
el.PNum(j) = sel.PNum(j);
}
}
el.SetIndex(1);
el.Invert();
mesh.AddVolumeElement(el);
numprisms++;
}
}
// Finally switch the point indices of the surface elements
// to the newly added ones
cout << "Transferring boundary layer surface elements to new vertex references...." << endl;
for (i = 1; i <= nse; i++)
{
Element2d & sel = mesh.SurfaceElement(i);
if(surfid.Contains(sel.GetIndex()))
{
for (j = 1; j <= sel.GetNP(); j++)
{
// Check (Doublecheck) if the corresponding point has a
// copy available for remapping
if (mapto.Get(sel.PNum(j)))
{
// Map the surface elements to the new points
sel.PNum(j) = mapto.Get(sel.PNum(j));
}
}
}
}
// Lock all the prism points so that the rest of the mesh can be
// optimised without invalidating the entire mesh
for (PointIndex pi = mesh.Points().Begin(); pi < mesh.Points().End(); pi++)
{
if(bndnodes.Test(i)) mesh.AddLockedPoint(pi);
}
// Now, actually pull back the old surface points to create
// the actual boundary layers
cout << "Moving and optimising boundary layer points...." << endl;
for (i = 1; i <= np; i++)
{
Array<ElementIndex> vertelems;
if(bndnodes.Test(i))
{
MeshPoint pointtomove;
pointtomove = mesh.Point(i);
if(layer == prismlayers)
{
mesh.Point(i).SetPoint(pointtomove + layerht * growthvectors.Elem(i));
meshtopo.GetVertexElements(i,vertelems);
for(j = 1; j <= vertelems.Size(); j++)
{
// double sfact = 0.9;
Element volel = mesh.VolumeElement(vertelems.Elem(j));
if(((volel.GetType() == TET) || (volel.GetType() == TET10)) && (!volel.IsDeleted()))
{
//while((volel.Volume(mesh.Points()) <= 0.0) && (sfact >= 0.0))
//{
// mesh.Point(i).SetPoint(pointtomove + (sfact * layerht * growthvectors.Elem(i)));
// mesh.ImproveMesh();
// // Try to move the point back by one step but
// // if the volume drops to below zero, double back
// mesh.Point(i).SetPoint(pointtomove + ((sfact + 0.1) * layerht * growthvectors.Elem(i)));
// if(volel.Volume(mesh.Points()) <= 0.0)
// {
// mesh.Point(i).SetPoint(pointtomove + (sfact * layerht * growthvectors.Elem(i)));
// }
// sfact -= 0.1;
//}
volel.Delete();
}
}
mesh.Compress();
}
else
{
mesh.Point(i).SetPoint(pointtomove + layerht * growthvectors.Elem(i));
}
}
}
}
// Optimise the tet part of the volume mesh after all the modifications
// to the system are completed
//OptimizeVolume(mparam,mesh);
cout << "New NP: " << mesh.GetNP() << endl;
cout << "Num of Quads: " << numquads << endl;
cout << "Num of Prisms: " << numprisms << endl;
cout << "Boundary Layer Generation....Done!" << endl;
dbg.close();
}
