An accelerometer balance for aerodynamic force measurements over Hypervelocity Ballistic models in shock tunnel

Abstract

A force balance to measure drag, lift and pitching moment over Hypervelocity Ballistic (HB) models 1 and 2 has been developed and assessed in an impulse test facility, hypersonic shock tunnel. The experiments were carried out at different angles of incidence of the models with the freestream at nominal Mach numbers of 5.78 and 8.31. The force balance is provided with rubber supports to ensure unrestrained motion of the model during the hypersonic freestream flow. Three dimensional finite element simulations are carried out to assess the performance of the force balance system in measuring the acceleration within the short test duration available in the shock tunnel. The force balance is mounted inside the model and is equipped with accelerometers to sense the model's acceleration in the desired direction. The aerodynamic force and moment coefficients are then deduced from the measured acceleration signals based on theories in aerodynamics. The measured values of force and moment coefficients match well with the theoretical values estimated using modified Newtonian theory for HB 1 and HB 2 models. In addition, CFD simulations are carried out for the experimental test cases using viscous, laminar models and the numerically computed force coefficients are validated by comparing against the experimental values. The present study demonstrates the use of accelerometer based force balance for measuring aerodynamic forces and moments over realistic long missile configurations.