Shear Viscosity under Shock-Loading Conditions

Although we rarely see a shock wave in everyday life, we experience them upon hearing the sound of an explosion, the bang of a gunshot, or the crack of a whip. In addition, objects that travel at supersonic speeds, such as bullets and missiles, also generate shock waves. During a typical shock-loading process, large pressures generated at the shock front can lead to an increase in the reactants’ reactivity via decomposition, as well as changes in mechanical and structural properties. Consequently, the initiation of shock waves often changes the nature of a reaction and, therefore, its final products. In a fluid’s case, we can study the impact of a shock wave through variables that describe physical properties of the materials on both sides of the shock front, i.e. density, temperature, and particle velocity. As a result, shear viscosity, which measures a system’s resistance to flow as a function of the relative velocity of adjacent layers of particles, is changed drastically under shock-loading conditions. More specifically, when a fluid is shocked, particles behind the shock front experience both a compressive force and a shear force, which together push particles away from their original equilibrium positions. In this process of deformation, shear viscosity largely depends on the speed of the relative movements between adjacent layers of particles. To describe this type of shock-activated process, we need to solve the momentum conservation equation, i.e. the Navier-Stokes equation,