Using ring strain sensors to measure dynamic forces in wind-tunnel testing

The paper deals with the use of strain-gage based ring-sensors to measure the dynamic forces involved in wind-tunnel testing for research of aeroelastic instabilities. In these experiments, the model has to be supported by an elastic suspension system that allows it to move in response to the flow. The motivation for the work here reported was the assessment of the possibility of occurrence of aeroelastic instabilities in a sectional model of a bridge deck under the action of lateral wind. The model is suspended by helical springs linked to four ring-sensors and aerodynamic drag is measured by two other ring-sensors. The entire measuring system stands outside the wind-tunnel and proved to be practical, low-cost and adaptable to other sectional models. The paper describes the development process and evaluation results of the ring sensors. They feature strain gages arranged in full Wheatstone bridge circuit. The measured time series of force values were translated into lift, pitch moment and drag, as well as linear and angular displacements of the model. High quality results were obtained with the assembly, which allowed obtaining the aerodynamic parameters sought.