In a bubble test, air is blown in front of the spinning propeller to visualize the flow of the water. This revealed some stalling on the bi-blade and the toroidal design too, which would explain ...

For boats, a propeller used for propulsion can either interact with the water or the air through which the boat is ... For human powered systems the efficiency must be as high as possible and the ...

"And I think (our students) had a lot of qualifiers: deliver gasoline for generators; deliver food, water ... said their design is not a four-propeller, photo-taking real estate drone.