double x_load = 0.2; // Target x-coordinate for load
double y_load = 0.2; // Target y-coordinate for load
double load = 1e-9; // Load, volume charge
double dist = 10.0; // Distance to (x_load,y_load) from degree of freedom
int index = 0; // Index of the degree of freedom closest to (x_load,y_load)
// Clear any previous model.
// Create a new model component.
model.modelNode().create(“comp1”);
// Create the 2D geometry.
model.geom().create(“geom1”, 2);
model.geom(“geom1”).feature().create(“sq1”, “Square”);
model.geom(“geom1”).run();
model.mesh().create(“mesh1”, “geom1”);
model.mesh(“mesh1”).feature().create(“fre1”, “FreeTri”);
model.mesh(“mesh1”).run();
// Setup the electrostatics physics problem.
model.physics().create(“es”, “Electrostatics”, “geom1”);
model.physics(“es”).feature().create(“gnd1”, “Ground”, 1);
model.physics(“es”).feature(“gnd1”).selection().set(new int[]{1});
model.physics(“es”).feature().create(“sfcd1”, “SurfaceChargeDensity”, 1);
model.physics(“es”).feature(“sfcd1”).selection().set(new int[]{4});
// Add a varying distributed charge density along the rightmost boundary.
model.physics(“es”).feature(“sfcd1”).set(“rhoqs”, “1e-9*y”);
model.component(“comp1”).physics(“es”).feature(“ccn1”).set(“epsilonr_mat”, “userdef”);
model.component(“comp1”).physics(“es”).feature(“ccn1”).set(“epsilonr”, “1”);
// Change to 1st order shape functions, to keep things simple.
model.component(“comp1”).physics(“es”).prop(“ShapeProperty”).
set(“order_electricpotential”, 1);
// Create and run the study.
model.study().create(“std1”);
model.study(“std1”).feature().create(“stat1”, “Stationary”);
model.study(“std1”).run();
// Create a 2D plot group with a surface plot for the original problem.
model.result().create(“pg1”, 2);
model.result(“pg1”).set(“data”, “dset1”);
model.result(“pg1”).feature().create(“surf1”, “Surface”);
selectNode(model.result(“pg1”)); // Set focus on the plot node.
// Create a reusable solver feature variable.
model.study().create(“std2”); // Create a Study 2 node.
model.sol().create(“sol2”); // Create a dataset Solution 2.
// Create a Solver configurations node under Study 2
model.sol(“sol2”).study(“std2”);
model.sol(“sol2”).create(“st1”, “StudyStep”); // Create a Compile Equations node.
solft = model.sol(“sol2”).feature(“st1”); // Assign solver step to variable solver.
solft.set(“study”, “std2”);
model.sol(“sol2”).create(“v1”, “Variables”); // Create a Dependent Variables node.
solft = model.sol(“sol2”).feature(“v1”);
model.sol(“sol2”).attach(“std2”);
model.sol(“sol2”).create(“a1”, “Assemble”); // Add an Assemble node.
solft = model.sol(“sol2”).feature(“a1”);
// Now define which system matrices should be output (Non-Eliminated Output).
// L=Load vector, K=Stiffness matrix, M=Constraint vector, N=Constraint Jacobian
// For more information see the Programming Reference Manual.
//Create a Stationary Solver 2 node: Study 2>Solver Configurations>Solution 2.
model.sol(“sol2”).create(“s2”, “Stationary”);
// Create an Input Matrix node under Stationary Solver 2.
solft = model.sol(“sol2”).feature(“s2”).create(“im1”, “InputMatrix”);
// Define which system matrices should be input.
// Find the degree of freedom coordinate closest to the target coordinate.
solft = model.sol(“sol2”).feature(“v1”);
XmeshInfo xmi = solft.xmeshInfo();
XmeshInfoDofs mydofs = xmi.dofs();
double[][] coords = mydofs.gCoords();
int[] coordsize = matrixSize(coords);
for (int k = 0; k < coordsize[1]; k++) {
new_dist = Math.sqrt((coords[0][k]-x_load)*(coords[0][k]-x_load)+ (coords[1][k]-y_load)*(coords[1][k]-y_load));
// Run the solver sequence up to and including the Assemble node.
model.sol(“sol2”).runFromTo(“st1”, “a1”);
// Extract system matrices and vectors.
solft = model.sol(“sol2”).feature(“a1”);
int KM = solft.getM(“K”);
int KN = solft.getN(“K”);
int KNnz = solft.getNnz(“K”);
int[] Ki = solft.getSparseMatrixRow(“K”);
int[] Kj = solft.getSparseMatrixCol(“K”);
double[] Kv = solft.getSparseMatrixVal(“K”);
// For more information, see the Programming Reference Manual.
double[] Lv = solft.getVector(“L”);
int NM = solft.getM(“N”);
int NN = solft.getN(“N”);
int NNnz = solft.getNnz(“N”);
int[] Ni = solft.getSparseMatrixRow(“N”);
int[] Nj = solft.getSparseMatrixCol(“N”);
double[] Nv = solft.getSparseMatrixVal(“N”);
double[] Mv = solft.getVector(“M”);
// Put the system matrices and vectors back in again.
solft = model.sol(“sol2”).feature(“s2”).feature(“im1”);
solft.createSparseMatrix(“K”, KM, KN, KNnz, true);
solft.addSparseMatrixVal(“K”, Ki, Kj, Kv);
solft.createVector(“L”, Lv.length, true);
solft.setVector(“L”, Lv);
solft.createSparseMatrix(“N”, NM, NN, NNnz, true);
solft.addSparseMatrixVal(“N”, Ni, Nj, Nv);
solft.createVector(“M”, Mv.length, true);
solft.setVector(“M”, Mv);
// Solve Stationary Solver 2 with the modified system.
model.sol(“sol2”).runFromTo(“s2”, “s2”);
model.result().create(“pg2”, “PlotGroup2D”);
with(model.result(“pg2”));
model.result(“pg2”).create(“surf1”, “Surface”);
// Plot electric potential and original mesh overlayed with no smoothing.
with(model.result(“pg2”).feature(“surf1”));
set(“resolution”, “norefine”);
model.result(“pg2”).create(“surf2”, “Surface”);
with(model.result(“pg2”).feature(“surf2”));
set(“resolution”, “norefine”);
set(“coloring”, “uniform”);
model.result(“pg2”).run();
selectNode(model.result(“pg2”)); // Set focus on the plot node.
در مثال قبلی، «دسترسی به گره‌های المان محدود با مرتبه بالاتر» در صفحه 204 ، از روش‌های XmeshInfoNodes برای دسترسی به گره‌های المان محدود استفاده می‌شود که طول آن‌ها با تعداد گره‌های المان محدود برابر است. در این مثال از متدهای XmeshInfoDofs برای دسترسی به بردار درجات آزادی استفاده می شود که طول آن برابر با بردار بار است.
توجه داشته باشید که فقط بردار بار اصلاح شده است. ماتریس ها و بردارهای دیگر فقط استخراج می شوند و سپس دوباره به سیستم بازگردانده می شوند.
