lift forces

Hi Dear All,
I facing one problem about lift coefficient. The drag value is good but even i run the code for Re=100 i npt get the value of lift. Can any one have such experience before and tell about the posibilities that why it’s happened. The forces i calculate like this

void get_force(int wall[NX][NY], int wb[NX][NY], double f_x, double f_y)
int i,j; f_x = 0.0; f_y = 0.0;
for(i=1;i<=NX-2;i++){ int ip = i+1; int im = i-1;
for(j=1;j<=NY-2;j++){ int jp = j+1; int jm = j-1;
f_x = f_x+(f_1[ip][j][1]+f_1[i][j][3]) (1-wall[ip][j]) - (f_1[im][j][3]+f_1[i][j][1]) (1-wall[im][j])
+ (f_1[ip][jp][5]+f_1[i][j][7])
(1-wall[ip][jp]) - (f_1[im][jp][6]+f_1[i][j][8])
- (f_1[im][jm][7]+f_1[i][j][5])
(1-wall[im][jm]) + (f_1[ip][jm][8]+f_1[i][j][6])

	        *f_y = *f_y+(f_1[i][jp][2]+f_1[i][j][4])*(1-wall[i][jp])   	- (f_1[i][jm][4]+f_1[i][j][2])*(1-wall[i][jm])
    		     	+ (f_1[ip][jp][5]+f_1[i][j][7])*(1-wall[ip][jp])+ (f_1[im][jp][6]+f_1[i][j][8])*(1-wall[im][jp])
       		        - (f_1[im][jm][7]+f_1[i][j][5])*(1-wall[im][jm]) - (f_1[ip][jm][8]+f_1[i][j][6])*(1-wall[ip][jm]);

		}		}	}

where wb i used for the solid objet like circular cylinder and wall means the computational domain NX and NY.

Then i calculate the drag and lift

cdx = -fx/rho0/ui/ui/radius;
cdy = -fy/rho0/ui/ui/radius;

fx and fy are basically the forces along x and y-axis that i calculate using the above function. The lift is implemented correctly, but don’t understand that even the convergence creiteria meet but still not find the values for lift coefficient for Re=100.
Any comments and suggestions will be highly appretciated.
Thanks in advance