Experimental and Numerical Investigation of Propeller Propulsion System Behavior Considering the Ground Effect

The aerodynamic characteristics of a propeller near the rigid ground and static water surface have been investigated numerically and experimentally. The aerodynamic performance of the propeller in various elevations from the ground and the static water surface and tilt angle settings at constant propeller rotational speed have been evaluated. The results indicated that ground and water surface can strongly affect the aerodynamic performance of rotating propellers in close distances up to 1.24 times its diameter. A decrease in the distance between the propeller rotation plane and the surface leads to a remarkable increase of the propeller efficiency up to 15%. Similarly, it has been found that the tilt angle has also noticeable effect on the near-surface aerodynamic characteristics of the propeller. At a tilt angle above 25° almost at any distance from the surface, near-surface effects tend to vanish and propeller thrust reaches its value of free flight condition. Drawing a comparison between near-ground thrust values of the propeller and the thrust values over the surface of water at any predetermined distance from surfaces and tilt angle indicated that the rigid ground has notably higher thrust efficiency than the flexible water surface. At a height of 0.3D (D is propeller diameter) from the ground surface, thrust increased by about 15% while the growth of thrust efficiency near the water surface was about 8%. CFD and Experimental results confirm each other.