Static calibration and dynamic behaviour of a six-component force balance for variable pressure water tunnel facilities

The presented six component force balance is a novel design used for many of the force measurements on hydrofoils and other bodies in the University of Tasmania's cavitation tunnel. This balance is a versatile piece of equipment, the distribution of its six load cells gives it a high degree of sensitivity and stiffness in all directions. The accuracy of the balance in operating conditions has yet to be defined and its use for investigations of low frequency fluid-structure interactions warrants an analysis of its dynamic properties. This paper outlines a critical analysis of the balances calibration methodologies and its measurement uncertainties. A dynamic vibration model was built and validated with finite element modelling and experiment to give a prediction of the force balances natural frequencies and how they change with different test article mass and added masses. These results provide confidence in the data produced by this device and guide future experimental investigations into fluid structure interactions.