drag calculation help
 

Hi, I have some code where I calculate the drag on an obstacle. In the code I calculate both the pressure drag and the viscous drag on a 2D structure mesh. I'm not certain I do this correct. Could someone confirm that this is correct?

I calculate the pressure drag by integrating the pressure over the left and right surfaces of the obstacle, for example

for(all nodes with right face exposed)
pressureDrag -= dy * pressure_to_right_of_node

for(all nodes with left face exposed)
pressureDrag += dy * pressure_to_left_of_node

The viscous drag is calculated by summing the force due to viscous effects over the top and bottom surfaces of the obstacle.

for(all nodes with top face exposed) {
float shearStress = mu * u[ijp1] / dy;
viscousDrag -= dx * ShearStress;
}
for(all nodes with bottom face exposed) {
float shearStress = mu * u[ijm1] / dy;
viscousDrag -= dx * ShearStress;
}

So basically for both types of drag I sum something over all the nodes directly outside the surface of the obstacle. Is this correct?

Thanks in advance for any help, it would be greatly appreciated.

any ideas? thank you