Development and Implementation of an Elastomeric Force Balance for the Evaluation of Drag Reduction Surfaces

A viscous force balance can provide rapid and accurate skin-friction measurements, enabling the performance evaluation of various drag reduction surfaces. In particular, the evaluation of riblet surfaces which refers to small scale, flow aligned ridges that have been shown to influence the turbulent boundary layer in a way that reduces viscous drag. The development and validation of an elastomeric force balance to provide this capability is discussed as well as its integration with a low speed wind tunnel with the focus on surface interchangeability. The balance was validated using multiple surfaces with different characteristics where additional skin-friction measurement techniques were applicable. The result is an instrument that produces measurements in agreement with other techniques, and is capable of discerning small changes in skin-friction characteristics between surfaces. This was achieved through careful design considerations and calibration.