Directions

usmannazir (47)
In the code given below,
Line # 91 stores a value to the east of i=0 and j=0. using [k][k + 1] as index terms.
Line # 92 stores a value to the west of i=0 and j=0. using [k][k - 1] as index terms.
Line # 93 stores a value to the north of i=0 and j=0. using [k][k - Ky] as index terms.
Line # 94 stores a value to the south of i=0 and j=0 using [k][k + Ky] as index terms.

I want to ask what if I use index as [k+1][k + 1] and [k+1][k + 1], which direction will this point to?

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#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <iostream>
#define Kx 6
#define Ky 8
#define N 48
#define K 1.0 //thermal conductivity,
#define TR 300.0 //
#define TL 300.0 //
#define TT 380.0 //Panel Face /Bottom Temerature
#define TB 300.0 //M-chasiss Face
#define aT 1.0 //relaxation factor (energy)
#define localre 0.001 //local residual for iterative method to solve matrix
#define localiter 50  //local iteration
using namespace std;

int main()
{
 int i, j, js;
 double S[N]; //source term
 double l; //Localre 
 double K_Tstar[Ky][Kx];/// Previous stage temperature value
 double T[Ky][Kx];//// Current stage temperature value
 double Mk[N];// Arrangement for Matrix Breakdown
 double Lex, Ley, dx, error, dy;//// Length direction variable
 double aP, aE, aW, aS, aN;
 double ke, kw, ks, kn;// Heat transfer coefficient
 dx = 1.0 / Kx;
 dy = 1.0 / Ky;
 ke = dy / dx;
 kw = dy / dx;
 ks = dx / dy;
 kn = dx / dy;
 int Ms;	//T initialize
 for (i = 0; i < Ky; i++)
 {
   for (j = 0; j < Kx; j++)
   {
     T[i][j] = 300.0;
   }
 }
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
for (Ms = 0; Ms < localiter; Ms++)
{
  int x = 0;
  int k = 0;//
  //arrange u, v, source, p_prime to 1'col matrix
  for (i = 0; i < Ky; i++)
  {
    for (j = 0; j < Kx; j++)
    {
       S[k] = 0.0;
       l = 0.0;
       Mk[k] = T[i][j];
       K_Tstar[i][j] = T[i][j];
       k++;
    }
}
 double **kP_T = NULL;// Memory Area Allocation
 kP_T = new double *[N];
  for (i = 0; i < N; i++)
  {
    kP_T[i] = new double[N];
  }
  for (i = 0; i < N; i++)
  {
    for (j = 0; j < N; j++)
    {
     kP_T[i][j] = 0.0;
    }
  }
//??? ??// Insert Initial Value
  for (i = 0; i < N; i++)
  {
   for (j = 0; j < N; j++)
    {
     kP_T[i][j] = 0.0;
    }
  }
 //T - matrix coefficient
  k = 0;
  for (i = 0; i < Ky; i++)
  {
   for (j = 0; j < Kx; j++)
    {
     if (i == 0)
      {
      if (j == 0) // bottom node, left column
       {
	kP_T[k][k + 1] = -ke;
	kP_T[k][k - 1] = -kw;
        kP_T[k][k - Ky] = -kn;
        kP_T[k][k + Ky] = -ks;
	kP_T[k][k] = -kP_T[k][k + 1] - kP_T[k][k + Ky] + 2.0*kn + 2.0*kw;
	S[k] = 2.0 * kw*TL + 2.0 * kn*TT;
	k++;
	cout << kP_T[k][k] << endl;
       }
      }
    }
  }
}
return 0;
}
Last edited on
dutch (2548)
The code doesn't seem to make sense.
Where did you get it from?
What are all the strange question marks for?
usmannazir (47)
It actually cut a part of a big code, which I am trying to understand. The questions marks are nothing just ignor them.
salem c (3700)
1. Add some convenience variables.
2. Rename some of the cryptic 1 and 2 letter variables to be something more meaningful.
3. Add more detail to any debugging you have.
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    int east = k + 1;
    int south= k + Ky;
    kP_T[k][east] = -ke;
    kP_T[k][south] = -ks;
    kP_T[k][k] = -kP_T[k][east] -   // aka +ke
                  kP_T[k][south] +  // aka +ks
                  2.0*kn +
                  2.0*kw;
    S[k] = 2.0 * kw*TLeft + 2.0 * kn*TTop;
    k++;
    cout << "k=" << k << ", KP_T=" << kP_T[k][k] << endl;
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