Unsteady Force Measurements in Pitching-Plunging Airfoils

Abstract

A new sensor for unsteady force measurements of pitching and plunging airfoils using Fiber Bragg Gratings (FBG) in a water channel facility has been the developed. Load cells having four or five FBG sensors written in a single optical fiber have been developed to measure the strain at flexures designed and determine the normal and axial forces, the pitching moment and the temperature. The main advantage of the present approach compared to other designs using electrical strain gages is the simplicity of a single optical fiber carrying all the sensor information, and low noise. The design, compensation, calibration and application to force measurement on an airfoil at steady and unsteady flow conditions are described. The measurement results show the unsteady large lift coefficients produced during mild and deep stall in a pitching and plunging SD 7003 airfoil.