Design and analysis of a flat accelerometer-based force balance system for shock tunnel testing

This paper describes the design and development of a accelerometer-based thin flat balance system for measuring aerodynamic forces on typical flight configurations in impulse facilities. The balance system is used to measure the axial force on a blunt-nosed triangular plate flying at Mach 5.75 in IISc hypersonic shock tunnel HST2 with a test flow duration of 800 μs. The model and the balance system are supported by rubber bushes, which leads to minimally restrained free floating conditions of the model in the test section during the flow duration. Exhaustive 3D finite element simulations are carried out to select appropriate rubber material. The measured and simulated values of axial force match very well with the theoretical values predicted using Newtonian theory at moderate specific enthalpy levels of the test gas. In addition, the importance of implementing the 3D-FEM analyses in design study of the accelerometer balance system has been highlighted by comparing the results of axi-symmetric modeling with 3D modeling.