Direct force measurement tests with hypersonic ducted model

Because of large errors of internal drag measurement based on the momentum theorem, the accuracy of Traditional Force Test with Ducted Models (TFTDM) is unable to meet the demands at hypersonic speeds. To solve this problem, a new experimental method for Force Direct-Test with Ducted Models (FDTDM) is presented. The testing aerodynamic forces acting on the airframe control volume of ducted models with sting-supported model are measured directly by a six-component balance. The related theoretical basis and the working principle of FDTDM are discussed. The testing ducted model is designed using the design experience of large scale models with internal and external flow decoupling. A wind tunnel test is conducted in FD-20A hypersonic wind tunnel, and the methodology and technology of FDTDM are verified by comparative analysis. The results indicate that the new experimental method based on the similarity theory and the force decomposition principles is feasible, and the measurements are accurate and credible. The information amount of experimental measurements is abundant, which could determine accurately the gas sealing effect. The accuracy of FDTDM is very high due to simplification of the procedure of internal drag measurement. The drag coefficient errors are less than 2% at free stream Mach number 6, which is far below that of TFTDM to meet the application requirements.