Unsteady force measurement for a beam using small piezoelectric end sensors

A new method to measure the total unsteady lift force across a propeller blade is presented in this paper. Unsteady forces across propeller blades are generated from the interaction of the blade boundary with a rotating pressure field associated with the propeller. The oscillating nature of the unsteady forces, particularly at higher harmonics, suggests that the unsteady lift fluctuations nearly cancel out over the blade span, and that it is possible to find the total unsteady force across the propeller from parameters at the root and tip. These parameters were determined from an approximation provided by the Method of the Stationary Phase. A newly designed apparatus for the measurement of total unsteady force across a propeller blade based on this theory is described in detail. For future experimental validation of the newly designed sensors, a propeller blade is modeled as a uniform beam, and a known unsteady force is generated across the beam surface.