How to calculate the extra lift gained by the intake lip of a duct? Aside from improving efficiency by preventing tip vortices, if a duct has a bell-shaped intake, this lip around the edge creates extra lift because the incoming air sticks to and curves around it which lowers it's pressure. This pressure difference between the duct lip surface and the surrounding air is what causes the extra lift.
The concept was used on the US military's Hillier Flying Platform with some success however, I cannot find any information on how to calculate the exact amount of lift generated by the duct lip for a given flow characteristic through the duct.
I made my own model but I have no idea if it's accurate, hence the need for experimental data to check it against.