The axial direction force would be nothing but thrust; it will be in the longitudinal
direction of the ship. So, that is the thrust, and the tangential direction force that is
generated for the propeller rotating in this thing. If there is a tangential directional force,
then that causes some moment around the propeller rotational axis and that is the torque.
You understood? This basic thrust and torque for each element we can calculate like that.
If we calculate all the axial forces and sum them up, then will get the total axial force,
and if we get the tangential force, take the moment about the rotational axis and sum all
the moments, then you will get the total torque absorbed by the propeller, is that clear?