Quasi one dimensional digital twin for blow-down supersonic wind tunnel

A fifty-year-old blow-down wind tunnel is subject to significant technical challenges, from mechanical to electronics and hydraulics. Besides the hardware and software aspects, the transition to a new crew needs computing tools that can be used, if not to train for the operation, at least to generate a basic understanding of the physical process, facility limitations and safety requirements. There are more reasons why to develop, possibly calibrate and use on a regular basis a digital twin for a blow-down wind tunnel: to produce estimates of the maximum run duration in high air consumption regimes, to assist in the initial regulating valve positioning in an attempt to mitigate the mechanical loads on the model and sting, to moderate the initial overshoot in stagnation pressure, etc. In the end, it is about finding the most suitable regimes and constraints, like blow-down splitting, for a customer’s test matrix. Compressor time and thus cost can be a priori estimated, although at some computational cost. Elements considered in the model are: tank, regulating valve and its actuation system with a basic control law, nozzle shaping, secondary throat and blockage induced by the model as a function of angle of attack. The useful time of the run is estimated considering the overshoot and settling time, together with the preset angle of attack program, until the end of the test. The response of the model is displayed against the original operating chart of the facility.