Improvement of a sensitivity-adjustable three component force balance and its application to supersonic wind tunnel testing

The objective of this study is to improve the performance of the sensitivity-adjustable three component force balance developed in the previous study for the usage of various experimental conditions. In the present study, balance shape is modified from the previous oval-shape to hexagonal-shape. First, the strain distribution for three kinds of balance shapes is deduced by FEM analysis to decide the strain gauge paste positions and the validity is confirmed by force balance calibration. Then, the characteristics of the sensitivity adjustability are investigated by FEM analysis and force balance calibration for various kinds of balance shapes. Finally, a hexagonal force balance is designed and applied to the wind tunnel experiment in a supersonic flow condition which is one of the severe experimental conditions. As a result, the use of hexagonal-shape enables us to improve the measurement accuracy because to paste strain gauges on appropriate positions is much easier for hexagonal-shape than for oval-shape. In addition, we can adjust the sensitivity ratio more extensively for hexagonal-shape than for oval-shape. The designed hexagonal force balance can measure aerodynamic forces in a supersonic flow condition. In conclusion, we can improve the performance of the sensitivity-adjustable three component force balance by the use of hexagonal-shape and apply to a supersonic wind tunnel experiment. In future, force balance calibration to investigate dynamic characteristics is required for a supersonic wind tunnel experiment.