UNSTEADY PROPELLER FORCES.
Technical memo. (thesis),
PENNSYLVANIA STATE UNIV UNIVERSITY PARK ORDNANCE RESEARCH LAB
Pagination or Media Count:
The problem of unsteady forces on a propeller operating in a non-uniform inflow and subjected to homogeneous, isotropic turbulence has been analyzed. Methods are presented for calculating the magnitude of the unsteady forces from these two causes. The theory is applied to a free-stream propeller operating in the wake of a single strut and in a turbulent flow. The calculations include variations of strut-to-propeller spacing, number of blades and blade sweep and show how unsteady forces are affected. In the case of a turbulent inflow, force spectra and the unsteady thrust coefficient are calculated. These quantities are seen to depend on two ratios the characteristic eddy size divided by the propeller diameter, and the characteristic eddy size divided by the propeller blade chord length. It is shown that the unsteady forces due to turbulence are of the same order of magnitude as those due to a non-uniform inflow. Author