Force recovery technique for multi component balances under impulsive loading in high speed flow experiments

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Accurate force measurement is a major concern in the design phase of any high speed vehicle in order to assess its stability and to estimate the fuel requirement. Evolution of new strategy for force prediction has to be authenticated by implementing the same in various impulse facilities like shock tube, shock tunnel, expansion tunnel etc. Force measurement experiments in such facilities are necessarily sophisticated due to the short duration. Further, inclusion of the whole system dynamics during force measurement studies is also a challenging task. Since stiffness based balance represents the system more accurately, present investigations mainly focus on the stiffness based force balances.To monitor the strain variation, usually strain gauge and pizofilm are opted as dynamic sensors in case of stress wave balance systems. Present study has been initiated to explore the types of configurations by which strain gauge can be connected in a Wheatstone bridge circuit. During dynamic calibration of the instrumented model and stress bar assembly, strain responses are captured and analyzed in temporal as well as frequency domain. This investigation reveals that half bridge circuit is more suitable for application in impulsive facilities. Further, piezofilm is also mounted on the model assembly and in order to assess the capabilities of both the sensors, the model is subjected to low supersonic flow environment in shock tube to measure the drag force. Drag force acting on the model during the experiment is predicted through de-convolution technique and Adaptive Neuro-Fuzzy Inference System (ANFIS) using the system response function derived from the dynamic calibration responses. Keeping in view of the good agreement between force obtained though experiments and numerical method, it is further planned to extend the application of ANFIS to multi component systems.
Supervisors: N. Sahoo and V. Kulkarni