Elastic Metamaterial-aided impulse aerodynamic Force measurement techniques

Wind tunnels play an important role in the early era of developing high-speed aircrafts.

And reproducing high-speed flight conditions above Mach 8 on the ground is usually restricted to impulse wind tunnels, whose test time lasts only several milliseconds. However conventional force measurement techniques requires a longer time.

Aerodynamic force measurement in such a short time is a great challenge, since measuring aerodynamic forces is crucial in wind tunnel tests. The stress wave force measurement technqiue shows to be quite suitable for force measurement in impulse facilities.

However, decoupling response signals to stress waves is still phenomenologically processed, resulting in rough force measurement results.

Indeed, that the elastic waves propagate in the sound speed, which is almost equal to the flow speed, is the basis for the stress wave balance (SWB).

So separating elastic waves and shielding reflected waves, the key in designing SWB, are an elastic wave propagation problem.

Elastic metamaterial (EMM), a kind of artificial material, has the designable frequency bandgaps, which can be used to guide waves.

Hence EMM will be a good choice for developing new SWB to accurately measure impulse aerodynamic forces.Then the challenging scientific and technical problem is two inverse problems: one is how to inversely design EMM, the other is how to inversely estimate forces.

With a forward-modelling knowledge on EMM, a parameterized objective function will be generated and a multi-objective optimization algorithm will be applied to solve the problem of inversely designing EMM. When the response signals are decoupled, identifying aerodynamic forces will be a typical inverse problem.

A fuzzy inference method will be developed to solve such an inverse problem with the aid of impulse response functions that acquired by calibration tests. Experiments in lab will be used to validate and optimize the inversely designed EMM and force identification scheme.