# Drag coefficient simulation problem

I tried to replicate the naca 4415 simulation, (naca4415_re2x10e6.sym), and the force coefficient vs Alpha in y position (Lift) seems to be the same as the original simulation, but I can't obtain the same values in the force coefficient Drag vs Alpha plot than the original simulation. I tried three times with the same results, starting with downloading and importing to Caedium the Naca 4415.brp file, using the same values from the original simulation, scalar and vector fields, scalar and vector variables, solver parameters, same physics, etc. The Drag vs Alpha plot show different values than the original. I want to replicate first this simulation before trying caedium in the airfoil I want to use in my glider proyect.

Is any tip or any missing step that can't be watched in the original simulation, to make my simulations work?

The Drag coefficient vs Alpha plot have negative values for drag coefficient.This means that the direction of drag force is reversed, or I am missing something?

## Did you apply the rotation?

The example "NACA 4415 Airfoil Calculation" uses a special setup where we rotate the airfoil around an axis over time, keeping the onset flow constant, and then automatically perform a steady simulation at each time step when we play the simulation. Did you apply the rotation transform?

For this approach you need to transform your Cp results to account for the rotation around the axis. You can see the specially created results in the

ResultsTool Palette that provide the transformed Cp values.Just in case you are not aware - the Panel Flow (panel method) can not predict stall, so your lift value will be incorrect at high incidence. Also a panel method can not predict skin friction drag, so all your drag values will be under-predicted. For more accurate lift and drag you will need to use the RANS Flow approach. For more details see "Why Use a Panel Method?".