// Do these edges intersect?
// Inspired by paper: "A Vertex Program for Efficient Box-Plane Intersection"
// by Christof Rezk Salama and Andreas Kolb, 2005
bool IntersectEdges(int i,int j,Vector *Point,Vector *n)
{
// Vertices of edge ij
Vector Vertex_i = MakeCubeCorner(i); // vertex i
Vector Edge_ij = MakeCubeCorner(j); // vertex j
Edge_ij.x -=Vertex_i.x; // difference of coordinates
Edge_ij.y -=Vertex_i.y;
Edge_ij.z -=Vertex_i.z;
// Start calculating lambda
double lambda = -DotVectors(&Vertex_i,n); // numerator of lambda
double denom = DotVectors(&Edge_ij,n); // denominator of lambda
// Don't divide by zero
if(DbleEqual(denom,0.0))
{
return false; // colinear
}
// Calculate lambda
lambda = lambda/denom;
// if not in [0,1] then it doesn't intersect
if(lambda>1.0 || lambda<0.0) {
return false; // doesn't intersect
}
// Find point
Point->x = Vertex_i.x +lambda*Edge_ij.x;
Point->y = Vertex_i.y +lambda*Edge_ij.y;
Point->z = Vertex_i.z +lambda*Edge_ij.z;
return true; // it does intersect
}
// Adjust change in momentum for frictional contact in tangential direction
// If has component of tangential motion, calculate force depending on whether it is sticking or sliding
// When frictional sliding, find tangential force (times dt) and set flag, if not set flag false
// When friction heating is on, set Ftdt term and set hasFriction to true
// (hasFriction (meaning has frictional heating value) must be initialized to false when called)
// contactArea only provided if frictional law needs it
// Normally in contact when called, but some laws might want call even when not in contact. If return
// value is false, the contact should be treated as no contact
bool CoulombFriction::GetFrictionalDeltaMomentum(Vector *delPi,Vector *norm,double dotn,double *mredDE,double mred,
bool getHeating,double contactArea,bool inContact,double deltime,Vector *at) const
{
// indicate no frictional heat yet
*mredDE=-1.;
// stick and frictionless are easy and no heating
if(frictionStyle==STICK)
{ // stick conditions no change
return true;
}
else if(frictionStyle==FRICTIONLESS)
{ // remove tangential term
CopyScaleVector(delPi,norm,dotn);
return true;
}
// Rest implements friction sliding
// The initial delPi = (-N A dt) norm + (Sstick A dt) tang = dotn norm + dott tang
// where N is normal traction (positive in compression), A is contact area, and dt is timestep
// get unnormalized tangential vector and its magnitude
// tang = delPi - dotn norm
Vector tang;
CopyVector(&tang,delPi);
AddScaledVector(&tang,norm,-dotn);
double tangMag = sqrt(DotVectors(&tang,&tang));
// if has tangential motion, we need to change momemtum if frictional sliding is occuring
if(!DbleEqual(tangMag,0.))
{ ScaleVector(&tang,1./tangMag);
double dott = DotVectors(delPi,&tang);
// make it positive for comparison to the positive frictional force Sslide
if(dott < 0.)
{ ScaleVector(&tang,-1.);
dott = -dott;
}
// Let frictional sliding force be Sslide Ac dt = f(N) Ac dt
// Then if dott > Sslide Ac dt (which means Sstick>Sslide)
// a. Set delPi = dotn norm + Sslide Ac dt tang
// For example, Coulomb friction has Fslide dt = mu(dotn) so delPi = (norm - mu tang) dotn
double SslideAcDt = GetSslideAcDt(-dotn,dott,0.,mred,contactArea,inContact,deltime);
if(!inContact) return false;
if(dott > SslideAcDt)
{ CopyScaleVector(delPi,norm,dotn);
AddScaledVector(delPi,&tang,SslideAcDt);
// get frictional heating term as friction work times reduced mass
// As heat source need Energy/sec or divide by timestep*reduced mass
// Note: only add frictional heating during momentum update (when friction
// force is appropriate) and only if frictional contact heat is enabled.
if(getHeating)
{ if(at!=NULL)
{ double Vs = SslideAcDt*(dott-SslideAcDt);
AddScaledVector(at, delPi, -1./deltime);
double AsDt = SslideAcDt*DotVectors(at,&tang)*deltime;
if(AsDt>Vs)
{ //*mredDE = Vs*(Vs/AsDt-1.)+0.5*AsDt;
*mredDE = 0.5*Vs*Vs/AsDt;
}
else
*mredDE = Vs - 0.5*AsDt;
}
else
*mredDE = SslideAcDt*(dott-SslideAcDt);
}
}
}
// still in contact
return true;
}
// increment external load on a particle
// input is analysis time in seconds
// (only called when diffusion is active)
MatPtFluxBC *MatPtFluxBC::AddMPFlux(double bctime)
{
// condition value is g/(mm^2-sec), Divide by rho*csat to get potential flux in mm/sec
// find this flux and then add (times area) to get mm^3-potential/sec
MPMBase *mpmptr = mpm[ptNum-1];
MaterialBase *matptr = theMaterials[mpmptr->MatID()];
// Flux is a scalar and we need int_(face) F Ni(x) dA
// Since F is constant, only need integral which is done by CPDI methods
// which has be generalized to work for GIMP too
// We use X_DIRECTION for bcDIR for efficiency. For Silent BC, change to
// Normal direction to all caculation of n
Vector fluxMag;
ZeroVector(&fluxMag);
int bcDir=X_DIRECTION;
if(style==SILENT)
{ TransportProperties t;
matptr->GetTransportProps(mpmptr,fmobj->np,&t);
Tensor *D = &(t.diffusionTensor);
// D in mm^2/sec, Dc in 1/mm
if(fmobj->IsThreeD())
{ fluxMag.x = D->xx*mpmptr->pDiffusion[gGRADx] + D->xy*mpmptr->pDiffusion[gGRADy] + D->xz*mpmptr->pDiffusion[gGRADz];
fluxMag.y = D->xy*mpmptr->pDiffusion[gGRADx] + D->yy*mpmptr->pDiffusion[gGRADy] + D->yz*mpmptr->pDiffusion[gGRADz];
fluxMag.z = D->xz*mpmptr->pDiffusion[gGRADx] + D->yz*mpmptr->pDiffusion[gGRADy] + D->zz*mpmptr->pDiffusion[gGRADz];
}
else
{ fluxMag.x = D->xx*mpmptr->pDiffusion[gGRADx] + D->xy*mpmptr->pDiffusion[gGRADy];
fluxMag.y = D->xy*mpmptr->pDiffusion[gGRADx] + D->yy*mpmptr->pDiffusion[gGRADy];
}
bcDir = N_DIRECTION;
}
else if(direction==EXTERNAL_FLUX)
{ // csatrho = rho0 V0 csat/V (units g/mm^3)
double csatrho = mpmptr->GetRho()*mpmptr->GetConcSaturation()/mpmptr->GetRelativeVolume();
fluxMag.x = BCValue(bctime)/csatrho;
}
else
{ // coupled surface flux and ftime is bath concentration
// time variable (t) is replaced by c-cbath, where c is the particle potential and cbath is bath potential
varTime = mpmptr->pPreviousConcentration-GetBCFirstTime();
GetPosition(&varXValue,&varYValue,&varZValue,&varRotValue);
double currentValue = fabs(scale*function->Val());
if(varTime>0.) currentValue=-currentValue;
// csatrho = rho0 V0 csat/V (units g/mm^3)
double csatrho = mpmptr->GetRho()*mpmptr->GetConcSaturation()/mpmptr->GetRelativeVolume();
fluxMag.x = currentValue/csatrho;
}
// get corners and direction from material point
int cElem[4],numDnds;
Vector corners[4],tscaled;
double ratio = mpmptr->GetTractionInfo(face,bcDir,cElem,corners,&tscaled,&numDnds);
// compact CPDI nodes into list of nodes (nds) and final shape function term (fn)
// May need up to 8 (in 3D) for each of the numDnds (2 in 2D or 4 in 3D)
int nds[8*numDnds+1];
double fn[8*numDnds+1];
int numnds = CompactCornerNodes(numDnds,corners,cElem,ratio,nds,fn);
// add force to each node
int i;
for(i=1;i<=numnds;i++)
diffusion->AddFluxCondition(nd[nds[i]],DotVectors(&fluxMag,&tscaled)*fn[i],false);
return (MatPtFluxBC *)GetNextObject();
}
