On non-Newtonian effects in fluidic shock-absorbers

Shock-absorbers often involve throttling of viscous fluids through small orifices. This gives rise to high rates-of-strain and non-Newtonian behavior even in fluids which are commonly assumed Newtonian, which affects impact mitigation properties. We here derive an asymptotic approximation describing the dynamics of fluidic shock-absorbers while focusing on weak Carreau type non-Newtonian effects and annular geometries. We validate our model by numerical computations and experiments with a medium-sized shock-absorber used to mitigate the impact caused by a free-falling weight. We then leverage the theoretical model to calculate the shock-absorber's optimal geometry and present experimental results of the fabricated optimal configuration, showing good agreement with the theory and nearly optimal impact mitigation properties.