Unhandled exception error for bigger array sizes

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Hi I need to create arrays with large sizes and I've written below code. as long as x & y (array size) ate small, there is no problem. but as soon as I enter bigger numbers for them it gives below error and make me break. Unhandled exception at 0x778d15de in twoDacid.exe: 0xC0000005: Access violation.

here is the code:

#include "StdAfx.h"
#include "math.h"
#include "iostream"
#include "fstream"

using namespace std;


int _tmain(int argc, _TCHAR* argv[])
{
//////////////////////////////////////////////////// constants
double poro0=0.2;    // initial porosity
double mu=0.05;      // acid viscusity (cp)
double L=0.5;        // length of the core (cm)
double H=0.5;        // width of the core
double q=1/60;       // injection rate (cm3/s)
double A=H*H;        // core surface area (cm2)
double U0=q/A;       // initial velocity (cm/s)
double r0=1e-4;      // initial mean pore radius (cm)
double a0=50;        // initial interface area per unit volume (cm2/cm3)
double k0=1;         // initial permeability (md)
double C0=0.15;      // initial acid concentration (volume fraction)    
double ks=0.2;       // surface reaction rate constant (cm/s)
double Dm=4e-6;      // acid diffusivity (cm2/s)
double beta=2;       // Pore broadening parameter
double landaX=0.5;   // constant in axial dispersion
double landaT=0.1;   // constant in Transverse dispersion
double alfaos=0.5;   // constant in dispersion correlation
double alfa=100/2;   // gravimetric dissolving power of the acid (gr of rock / mole of acid) here for CaCO3 2moles of acid is...
                     //needed to dissolce 1 mole of rock ////////////// 100(gr/mol)*1mole / 2mole
double Pe=0;
double Ros=2.71;     // solid density (gr/cm3)
double Roa=1;        // acid density (gr/cm3)                    supposed to be constant

double phi2P=0.007;  //2*ks*r0/Dm; // pore scale thielie module
double phi2D=1e6;    //ks*a0*L^2/Dm; // Darcy scale thielie module
double Da=ks*a0*L/U0;     // damkohler number
double Nac=0.1;      //alfa*C0/Ros;   // acid capacity number
double eta=2*r0/L;

///////////////////////////////////////////////////// solution parameters
const int x=100;         // number of element in x direction
const int y=100;         // number of element in y direction
double dx=1.0/x;       // x block length (dimless)
double dy=(H/L)/y;
double endt=1;       // end time (s)
double endtD=(endt/L)*U0;  //dimless end time
const int T=100000;         // number of time steps
double dt=endtD/T;   // length of time steps

/////////////////////////////////////// initial valuse for parameters that vary with time:
double r[x][y];
double Av[x][y];
double K[x][y];
double u[x][y];
double Cf[x][y];
double ReP[x][y];
double Sh[x][y];
for (int i=0;i<=x-1;i++){
    for (int j=0;j<=y-1;j++){
        r[i][j]=1;
        Av[i][j]=1;
        K[i][j]=1;
        u[i][j]=1;
        Cf[i][j]=1;
        ReP[i][j]=2*Roa*U0*r0/mu;
        Sh[i][j]=3+7*(sqrt(ReP[i][j]));
    }
}

///////////////////////////////////////////////// heterogenous medium
double poro[x][y];
for (int i=0;i<=x-1;i++){
    for (int j=0;j<=y-1;j++){
        if (j==2 && i==0)
            poro[i][j ...