Shock viscosity

J. W. Swegle and D.E. Grady, Shock Viscosity and the Prediction of Shock Wave Rise... 

It is particularly significant that no evidence is found for localized melting at particle interfaces in the inorganic materials studied. Apparently, effects commonly observed in dynamic compaction of low shock viscosity metals are not obtained in the less viscous materials of the present study. To successfully predict the occurrence of localized melting, it appears necessary to develop a more realistic physical model of energy localization in shock-compressed powders. 

Intermetallics also represent an ideal system for study of shock-induced solid state chemical synthesis processes. The materials are technologically important such that a large body of literature on their properties is available. Aluminides are a well known class of intermetallics, and nickel aluminides are of particular interest. Reactants of nickel and aluminum give a mixture with powders of significantly different shock impedances, which should lead to large differential particle velocities at constant pressure. Such localized motion should act to mix the reactants. The mixture also involves a low shock viscosity, deformable material, aluminum, with a harder, high shock viscosity material, nickel, which will not flow as well as the aluminum. 

It was found out that oligoketones on the basis of diphenylolpropane, independently liom condensation degree, influence on HDPE as plasticizers. We can make a conclusion on these facts that there is some increasing of relative deformation during the destroying of models. But at the transition to phenolphthalein oligoketones there is an essential distinction, that is the polymer models become harder (the modulus of elasticity increases). Both the shock viscosity and the limit of forced stretchiness stay at high level which exceeds a little these parameters... 

The shock wave is subject to other dissipative effects, however, such as viscosity and heat transport. It is these dissipative mechanisms that are responsible for preventing the shock from becoming a true, infinitesimally thin discontinuity. In reality, the velocity gradient can only increase until... 

Miller, G.H., and Ahrens, T.J. (1991), Shock-Wave Viscosity Measurement, Rev. Modern Phys. 63, 919-948. 

W.F. Noh, Errors for Calculations of Strong Shocks Using an Artificial Viscosity and an Artificial Heat Flux, J. Comput. Phys. 72 (1978). 

The inelastic wave shows rise times that vary quite substantially. Recognizing that the rise time is a direct indication of the balance between the viscous response of the sample and the driving force, Grady [81G01] has analyzed and compared the effective viscosity of a range of materials. These viscosities are manifestations of the dynamic deformation controlled by the shock-induced defects, heterogeneities, and their motions. 

The code reproduced shock-jump conditions well, but many details in the solution were lost because of the smearing effect of artificial viscosity. 

Basic Breakup Modes. Starting from Lenard s investigation of large free-falling drops in still air,12671 drop/droplet breakup has been a subject of extensive theoretical and experimental studies[268] 12851 for a century. Various experimental methods have been developed and used to study droplet breakup, including free fall in towers and stairwells, suspension in vertical wind tunnels keeping droplets stationary, and in shock tubes with supersonic velocities, etc. These theoretical and experimental studies revealed that droplet breakup under the action of aerodynamic forces may occur in various modes, depending on the flow pattern around the droplet, and the physical properties of the gas and liquid involved, i.e., density, viscosity, and interfacial tension. 

It is convenient to use a simple weightless Hookean, or ideal, elastic spring with a modulus G and a simple Newtonian (fluid) dashpot or shock absorber having a liquid with a viscosity of 17 as models to demonstrate the deformation of an elastic solid and an ideal liquid, respectively. The stress-strain curves for these models are shown in Figure 14.1. 

The surface and bulk viscosities not only reduce the draining rate of the lamella but also help in restoration against mechanical, thermal, or chemical shocks. The highest foam stability is associated with appreciable surface viscosity (qs) and yield value. 

Figure 6. Set ofjump discontinuities (kinks and shocks) compatible with the isothermal viscosity-capillarity model W=2.5.

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