I have examined some of the original literature on the drag force models used. Am I correct in stating that when using the Koch Hill drag force model, the Archimedes buoyancy model should NOT be used as it is 'included' in the Koch Hill model by their definition of drag force? Or has the Koch Hill drag force model been modified by a factor of the fluid fraction to 'remove' the buoyancy term?
On the other hand, the Archimedes buoyancy force does need to used when using all the other drag force models, correct?