Esempio n. 1
0
void arrayops() {
  double nx = 10;
  double ny = 10;
  double nt = 100;
  double c = 1;
  double dx = 2/(nx-1);
  double dy = 2/(ny-1);
  double sigma = .2;
  double dt = sigma*dx;
  
  Eigen::ArrayXd x; // Array containing our x values
  x.setLinSpaced(nx,0,2);
  
  Eigen::ArrayXd y; // Array containing our x values
  y.setLinSpaced(ny,0,2);

  Eigen::ArrayXXd u;
  u.setOnes(ny,nx);
  
  Eigen::ArrayXXd un;
  un.setOnes(ny,nx);
  
  u.block(.5/dy,.5/dx,(1/dy+1)-.5/dy,(1/dx+1)-.5/dx) = Eigen::ArrayXXd::Constant((1/dy+1)-.5/dy,(1/dx+1)-.5/dx,2);
  
  int count;
  for(int i=0;i<nt;i++) {
    un << u;
    u.block(1,1,ny-1,nx-1) = un.block(1,1,ny-1,nx-1)-(c*dt/dx*(un.block(1,1,ny-1,nx-1)-un.block(0,1,ny-1,nx-1)))-(c*dt/dy*(un.block(1,1,ny-1,nx-1)-un.block(1,0,ny-1,nx-1)));
    
  }
  
  std::cout << u << std::endl;
 
}  
Esempio n. 2
0
void nonlin2d() {
  double nx = 101;
  double ny = 101;
  double nt = 80;
  double c = 1;
  double dx = 2/(nx-1);
  double dy = 2/(ny-1);
  double sigma = .2;
  double dt = sigma*dx;
  
  // Make an output folder
  std::string dir = "step6/";
  
  Eigen::ArrayXd x; // Array containing our x values
  x.setLinSpaced(nx,0,2);
  
  Eigen::ArrayXd y; // Array containing our x values
  y.setLinSpaced(ny,0,2);

  Eigen::ArrayXXd u;
  u.setOnes(ny,nx);
  Eigen::ArrayXXd v;
  v.setOnes(ny,nx);
  Eigen::ArrayXXd un;
  un.setOnes(ny,nx);
  Eigen::ArrayXXd vn;
  vn.setOnes(ny,nx);
    
  u.block(.5/dy, .5/dx, 1/dy+1-.5/dy, 1/dx+1-.5/dx) = Eigen::ArrayXXd::Constant(1/dy+1-.5/dy,1/dx+1-.5/dx,2);
  v.block(.5/dy, .5/dx, 1/dy+1-.5/dy, 1/dx+1-.5/dx) = Eigen::ArrayXXd::Constant(1/dy+1-.5/dy,1/dx+1-.5/dx,2);
  
  for(int i=0;i<nt+1;i++) {
    un << u;
    vn << v;
    
    u.block(1,1,ny-1,nx-1) = un.block(1,1,ny-1,nx-1)-(un.block(1,1,ny-1,nx-1)*dt/dx*(un.block(1,1,ny-1,nx-1)-un.block(0,1,ny-1,nx-1)))-(vn.block(1,1,ny-1,nx-1)*dt/dy*(un.block(1,1,ny-1,nx-1)-un.block(1,0,ny-1,nx-1)));
    v.block(1,1,ny-1,nx-1) = vn.block(1,1,ny-1,nx-1)-(un.block(1,1,ny-1,nx-1)*dt/dx*(vn.block(1,1,ny-1,nx-1)-vn.block(0,1,ny-1,nx-1)))-(vn.block(1,1,ny-1,nx-1)*dt/dy*(vn.block(1,1,ny-1,nx-1)-vn.block(1,0,ny-1,nx-1)));
    
    u.block(0,0,1,nx-1) = Eigen::ArrayXXd::Constant(1,nx-1,1);
    u.block(ny-1,0,1,nx-1) = Eigen::ArrayXXd::Constant(1,nx-1,1);
    u.block(0,0,ny-1,1) = Eigen::ArrayXXd::Constant(ny-1,1,1);
    u.block(0,nx-1,ny-1,1) = Eigen::ArrayXXd::Constant(ny-1,1,1);
    
    v.block(0,0,1,nx-1) = Eigen::ArrayXXd::Constant(1,nx-1,1);
    v.block(ny-1,0,1,nx-1) = Eigen::ArrayXXd::Constant(1,nx-1,1);
    v.block(0,0,ny-1,1) = Eigen::ArrayXXd::Constant(ny-1,1,1);
    v.block(0,nx-1,ny-1,1) = Eigen::ArrayXXd::Constant(ny-1,1,1);
  }
  
  ofstream writexdata((dir + "output.dat").c_str(), ios::out | ios::trunc);
  writexdata << u << endl;
  writexdata.close();
}
Esempio n. 3
0
void laplace2d() {
  double nx = 31;
  double ny = 31;
  double c = 1;
  double dx = 2/(nx-1);
  double dy = 2/(ny-1);
  double linorm_target = .01;
  double linorm = 1;
  
  // Make an output folder
  std::string dir = "step9/";
  
  Eigen::ArrayXd x; // Array containing our x values
  x.setLinSpaced(nx,0,2); // Array is linearly spaced values from 0 to 2
  
  Eigen::ArrayXd y; // Array containing our x values
  y.setLinSpaced(ny,0,1);
  
  // Arrays containing our calculated values
  Eigen::ArrayXXd p;
  Eigen::ArrayXXd pn;
  
  // Initial Conditions
  p.setZero(ny,nx);
  pn.setZero(ny,nx);
  
  //Set Boundary Conditions
  p.block(0,0,ny,1) = Eigen::ArrayXXd::Constant(ny,1,0);
  p.block(0,nx-1,ny,1) = y.block(0,0,ny,1);
  p.block(0,0,1,nx) = p.block(1,0,1,nx);
  p.block(ny-1,0,1,nx) = p.block(ny-2,0,1,nx);

  while(linorm>linorm_target)
  {
    pn << p;
    p.block(1,1,ny-2,nx-2) = (pow(dy,2)*(pn.block(2,1,ny-2,nx-2)+pn.block(0,1,ny-2,nx-2))+pow(dx,2)*(pn.block(1,2,ny-2,nx-2)+pn.block(1,0,ny-2,nx-2)))/(2*(pow(dx,2)+pow(dy,2)));
    p(0,0) = (pow(dy,2)*(pn(1,0)+pn(ny-1,0))+pow(dx,2)*(pn(0,1)+pn(0,nx-1)))/(2*(pow(dx,2)+pow(dy,2)));
    p(ny-1,nx-1) = (pow(dy,2)*(pn(0,nx-1)+pn(ny-2,nx-1))+pow(dx,2)*(pn(ny-1,0)+pn(ny-1,nx-2)))/(2*(pow(dx,2)+pow(dy,2)));
    
    //Set Boundary Conditions
    p.block(0,0,ny,1) = Eigen::ArrayXXd::Constant(ny,1,0);
    p.block(0,nx-1,ny,1) = y.block(0,0,ny,1);
    p.block(0,0,1,nx) = p.block(1,0,1,nx);
    p.block(ny-1,0,1,nx) = p.block(ny-2,0,1,nx);
   
    linorm = (p.cwiseAbs()-pn.cwiseAbs()).sum()/(pn.cwiseAbs()).sum();
    
  }
  
  ofstream writexdata((dir + "output.dat").c_str(), ios::out | ios::trunc);
  writexdata << p << endl;
  writexdata.close();
}