NAG Library Manual, Mark 27.2
Interfaces:  FL   CL   CPP   AD 

NAG CL Interface Introduction
Example description
/* nag_mesh_dim2_gen_front (d06acc) Example Program.
 *
 * Copyright 2021 Numerical Algorithms Group.
 *
 * Mark 27.2, 2021.
 */

#include <math.h>
#include <nag.h>
#include <stdio.h>

/* Structure to allow data to be passed onto */
/* the nag_mesh_dim2_gen_boundary (d06bac) user-supplied function fbnd */

struct user {
  /* details of the double NACA0012 and the circle around it */

  double x0, y0, x1, y1, radius;
};

#ifdef __cplusplus
extern "C" {
#endif
static double NAG_CALL fbnd(Integer, double, double, Nag_Comm *);
#ifdef __cplusplus
}
#endif

#define EDGE(I, J) edge[3 * ((J)-1) + (I)-1]
#define LINED(I, J) lined[4 * ((J)-1) + (I)-1]
#define CONN(I, J) conn[3 * ((J)-1) + (I)-1]
#define COOR(I, J) coor[2 * ((J)-1) + (I)-1]
#define COORCH(I, J) coorch[2 * ((J)-1) + (I)-1]

int main(void) {
  const Integer nus = 1, nvmax = 2000, nedmx = 200, nvint = 40;
  struct user geom_Naca;
  double dnvint, radius, x0, x1, y0, y1;
  Integer exit_status = 0, i, itrace, j, k, l, ncomp, nedge, nelt, nlines;
  Integer nv, nvb, nvint2, reftk;
  char pmesh[2];
  double *coor = 0, *coorch = 0, *coorus = 0, *rate = 0, *weight = 0;
  Integer *conn = 0, *edge = 0, *lcomp = 0, *lined = 0, *nlcomp = 0;
  NagError fail;
  Nag_Comm comm;

  INIT_FAIL(fail);

  printf(" nag_mesh_dim2_gen_front (d06acc) Example Program Results\n\n");

  /* Skip heading in data file */
  scanf("%*[^\n] ");

  /* Initialize boundary mesh inputs: the number of lines and */
  /* the number of characteristic points of the boundary mesh */
  scanf("%" NAG_IFMT "", &nlines);
  scanf("%*[^\n] ");

  /* Allocate memory */

  if (!(coor = NAG_ALLOC(2 * nvmax, double)) ||
      !(coorch = NAG_ALLOC(2 * nlines, double)) ||
      !(coorus = NAG_ALLOC(2 * nus, double)) ||
      !(rate = NAG_ALLOC(nlines, double)) ||
      !(weight = NAG_ALLOC(nvint, double)) ||
      !(conn = NAG_ALLOC(3 * (2 * nvmax + 5), Integer)) ||
      !(edge = NAG_ALLOC(3 * nedmx, Integer)) ||
      !(lined = NAG_ALLOC(4 * nlines, Integer)) ||
      !(lcomp = NAG_ALLOC(nlines, Integer))) {
    printf("Allocation failure\n");
    exit_status = -1;
    goto END;
  }

  /* The double NACA0012 and the circle around it */
  for (j = 1; j <= nlines; ++j)
    scanf("%lf", &COORCH(1, j));
  scanf("%*[^\n] ");
  for (j = 1; j <= nlines; ++j)
    scanf("%lf", &COORCH(2, j));
  scanf("%*[^\n] ");

  /* The lines of the boundary mesh */

  for (j = 1; j <= nlines; ++j) {
    for (i = 1; i <= 4; ++i)
      scanf("%" NAG_IFMT "", &LINED(i, j));
    scanf("%lf", &rate[j - 1]);
  }
  scanf("%*[^\n] ");

  /* The number of connected components to */
  /* the boundary and their information */
  scanf("%" NAG_IFMT "", &ncomp);
  scanf("%*[^\n] ");

  /* Allocate memory */

  if (!(nlcomp = NAG_ALLOC(ncomp, Integer))) {
    printf("Allocation failure\n");
    exit_status = -1;
    goto END;
  }

  j = 0;
  for (i = 0; i < ncomp; ++i) {
    scanf("%" NAG_IFMT "", &nlcomp[i]);
    scanf("%*[^\n] ");
    l = j + NAG_IABS(nlcomp[i]);
    for (k = j; k < l; ++k)
      scanf("%" NAG_IFMT "", &lcomp[k]);
    scanf("%*[^\n] ");

    j += NAG_IABS(nlcomp[i]);
  }
  scanf(" ' %1s '%*[^\n]", pmesh);

  /* Data passed to the user-supplied function */

  x0 = 1.5;
  y0 = 0.0;
  radius = 4.5;
  x1 = 0.8;
  y1 = -0.3;

  comm.p = (Pointer)&geom_Naca;

  geom_Naca.x0 = x0;
  geom_Naca.y0 = y0;
  geom_Naca.radius = radius;
  geom_Naca.x1 = x1;
  geom_Naca.y1 = y1;

  itrace = 0;

  /* Call to the 2D boundary mesh generator */

  /* nag_mesh_dim2_gen_boundary (d06bac).
   * Generates a boundary mesh
   */
  nag_mesh_dim2_gen_boundary(nlines, coorch, lined, fbnd, coorus, nus, rate,
                             ncomp, nlcomp, lcomp, nvmax, nedmx, &nvb, coor,
                             &nedge, edge, itrace, 0, &comm, &fail);

  if (fail.code == NE_NOERROR) {
    if (pmesh[0] == 'N') {
      printf(" Boundary mesh characteristics\n");
      printf(" nvb   =%6" NAG_IFMT "\n", nvb);
      printf(" nedge =%6" NAG_IFMT "\n", nedge);
    } else if (pmesh[0] == 'Y') {
      /* Output the mesh to view it using the NAG Graphics Library */

      printf(" %10" NAG_IFMT " %10" NAG_IFMT "\n", nvb, nedge);

      for (i = 1; i <= nvb; ++i)
        printf("  %4" NAG_IFMT "  %15.6e  %15.6e  \n", i, COOR(1, i),
               COOR(2, i));

      for (i = 1; i <= nedge; ++i)
        printf(" %4" NAG_IFMT " %4" NAG_IFMT " %4" NAG_IFMT " %4" NAG_IFMT "\n",
               i, EDGE(1, i), EDGE(2, i), EDGE(3, i));
    } else {
      printf("Problem with the printing option Y or N\n");
      exit_status = -1;
      goto END;
    }
  } else {
    printf("Error from nag_mesh_dim2_gen_boundary (d06bac).\n%s\n",
           fail.message);
    exit_status = 1;
    goto END;
  }

  /* Initialize mesh control parameters */

  itrace = 0;

  /* Generation of interior vertices */
  /* for the wake of the first NACA */

  nvint2 = nvint / 2;
  dnvint = 5.0 / (nvint2 + 1.0);

  for (i = 1; i <= nvint2; ++i) {
    reftk = nvb + i;
    COOR(1, reftk) = i * dnvint + 1.0;
    COOR(2, reftk) = 0.0;
    weight[i - 1] = 0.05;
  }

  /* for the wake of the second one */

  dnvint = 4.19 / (nvint2 + 1.0);

  for (i = nvint2 + 1; i <= nvint; ++i) {
    reftk = nvb + i;
    COOR(1, reftk) = (i - nvint2) * dnvint + 1.8;
    COOR(2, reftk) = -0.3;
    weight[i - 1] = 0.05;
  }

  /* Call to the 2D Advancing front mesh generator */

  /* nag_mesh_dim2_gen_front (d06acc).
   * Generates a two-dimensional mesh using an Advancing-front
   * method
   */
  nag_mesh_dim2_gen_front(nvb, nvint, nvmax, nedge, edge, &nv, &nelt, coor,
                          conn, weight, itrace, 0, &fail);

  if (fail.code == NE_NOERROR) {
    if (pmesh[0] == 'N') {
      printf(" Complete mesh characteristics\n");
      printf("   nv (rounded to nearest 10) =%6" NAG_IFMT "\n",
             10 * ((nv + 5) / 10));
      printf(" nelt (rounded to nearest 10) =%6" NAG_IFMT "\n",
             10 * ((nelt + 5) / 10));
    } else if (pmesh[0] == 'Y') {
      /* Output the mesh to view it using the NAG Graphics Library */

      printf(" %10" NAG_IFMT " %10" NAG_IFMT "\n", nv, nelt);

      for (i = 1; i <= nv; ++i)
        printf("  %15.6e  %15.6e\n", COOR(1, i), COOR(2, i));

      reftk = 0;
      for (k = 1; k <= nelt; ++k)
        printf(" %10" NAG_IFMT "%10" NAG_IFMT "%10" NAG_IFMT "%10" NAG_IFMT
               "\n",
               CONN(1, k), CONN(2, k), CONN(3, k), reftk);
    } else {
      printf("Problem with the printing option Y or N\n");
      exit_status = -1;
      goto END;
    }
  } else {
    printf("Error from nag_mesh_dim2_gen_front (d06acc).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }

END:
  NAG_FREE(coor);
  NAG_FREE(coorch);
  NAG_FREE(coorus);
  NAG_FREE(rate);
  NAG_FREE(weight);
  NAG_FREE(conn);
  NAG_FREE(edge);
  NAG_FREE(lcomp);
  NAG_FREE(lined);
  NAG_FREE(nlcomp);

  return exit_status;
}

double NAG_CALL fbnd(Integer i, double x, double y, Nag_Comm *pcomm) {
  double ret_val;
  double c, radius, x0, x1, y0, y1;
  struct user *geom_Naca = (struct user *)pcomm->p;

  x0 = geom_Naca->x0;
  y0 = geom_Naca->y0;
  radius = geom_Naca->radius;
  x1 = geom_Naca->x1;
  y1 = geom_Naca->y1;

  ret_val = 0.0;

  switch (i) {
  case 1:

    /* upper NACA0012 wing beginning at the origin */

    c = 1.008930411365;

    ret_val = 0.6 * (0.2969 * sqrt(c * x) - 0.126 * (c * x) -
                     0.3516 * pow(c * x, 2.0) + 0.2843 * pow(c * x, 3.0) -
                     0.1015 * pow(c * x, 4.0)) -
              c * y;
    break;

  case 2:

    /* lower NACA0012 wing beginning at the origin */

    c = 1.008930411365;

    ret_val = 0.6 * (0.2969 * sqrt(c * x) - 0.126 * (c * x) -
                     0.3516 * pow(c * x, 2.0) + 0.2843 * pow(c * x, 3.0) -
                     0.1015 * pow(c * x, 4.0)) +
              c * y;

    break;

  case 3:

    /* the circle around the double NACA */

    ret_val = (x - x0) * (x - x0) + (y - y0) * (y - y0) - radius * radius;
    break;

  case 4:

    /* upper NACA0012 wing beginning at (X1;Y1) */

    c = 1.008930411365;

    ret_val = 0.6 * (0.2969 * sqrt(c * (x - x1)) - 0.126 * c * (x - x1) -
                     0.3516 * pow(c * (x - x1), 2.0) +
                     0.2843 * pow(c * (x - x1), 3.0) -
                     0.1015 * pow(c * (x - x1), 4.0)) -
              c * (y - y1);
    break;

  case 5:

    /* lower NACA0012 wing beginning at (X1;Y1) */

    c = 1.008930411365;

    ret_val = 0.6 * (0.2969 * sqrt(c * (x - x1)) - 0.126 * (c * (x - x1)) -
                     0.3516 * pow(c * (x - x1), 2.0) +
                     0.2843 * pow(c * (x - x1), 3.0) -
                     0.1015 * pow(c * (x - x1), 4.0)) +
              c * (y - y1);
    break;
  }

  return ret_val;
}