fdtd_1_1.cpp

FDTD 1-d C++ sourece

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

 # define KE 200              /* KE is the number of cells to be used */

 void main ()
 {
  float ex[KE],hy[KE];         
  int n,k,kc,ke,NSTEPS;
  float T;
  float t0,spread,pulse;

  FILE *fp;

  /* Initialize */
  for ( k=0; k<KE; k++)            /*此处应为k=0,不然得不到书中图形,因为ex[0]hy[0]为垃圾值
	                                 会随波动传播出去*/
  {
   ex[k] = 0;
   hy[k] = 0;
  }
 
  kc = KE/2;                    /* Center of the problem space */
  t0 = 40.0;                    /* Center of the incident pulse */
  spread = 12;                  /* Width of the incident pulse */
  NSTEPS = 1;
  T = 0;

  while (NSTEPS>0)
  {
   printf ("NSTEPS -->  ");   /* NSTEPS is the number of times the */
   scanf (" %d", &NSTEPS);    /* main loop has executed */
   printf (" %d \n",NSTEPS);
   n = 0;
   

   for ( n=1; n<=NSTEPS; n++)
   {
    T = T+1;                        /* T keeps track of the total number */
		                    		/* of times the main loop is executed */
    /* Main FDTD Loop */

    /* Calculate the Ex field */
    for ( k=1; k<KE; k++)
    {
     ex[k] = ex[k]+.5*(hy[k-1]-hy[k]);
    }

    /* Put a Gaussian pulse in the middle */

    pulse = exp(-.5*(pow((t0-T)/spread,2.0)));
    ex[kc] = pulse;
    printf ("%5.1f %6.2f \n",t0-T,ex[kc]);

    /* Calculate the Hy field */
    for ( k=0; k<KE-1; k++)
    {
     hy[k]=hy[k]+.5*(ex[k]-ex[k+1]);
    }

   }

    /* End of the Main FDTD Loop */

	/* At the end of the calculation,print out
	  the Ex and Hy fields */
    for (k=0;k<KE;k++)
    {
     printf ("%3d  %6.2f  %6.2f \n",k,ex[k],hy[k]);
    }

    /* Write the E field out ot a file "Ex" */
    fp=fopen( "Ex","w");
    for (k=0;k<KE;k++)
    {
     fprintf (fp," %6.2f \n",ex[k]);
    }
    fclose(fp);

    /* Write the H field out ot a file "Hy" */
    fp=fopen( "Hy","w");
    for (k=0;k<KE;k++)
    {
     fprintf (fp," %6.2f \n",hy[k]);
    }
    fclose(fp);

    printf("T= %5.0f \n",T);
  }
 }