Experimental investigation of the interaction of a plane, oblique, incident-reflecting shock wave with a turbulent boundary layer on a cooled surface. Volume 2 - Basic plotted data

Interaction of plane, oblique, incident reflecting shock wave with turbulent boundary layer on cooled surface - graph

Pressure versus impulse graph for blast-induced traumatic brain injury and correlation to observable blast injuries

With the increased use of explosive devices in combat, blast induced traumatic brain injury (bTBI) has become one of the signature wounds in current conflicts. Animal studies have been conducted to understand the mechanisms in the brain and a pressure versus time graph has been produced. However, the role of impulse in bTBIs has not been thoroughly investigated for animals or human beings. This research proposes a new method of presenting bTBI data by using a pressure versus impulse (P-I) graph. P-I graphs have been found useful in presenting lung lethality regions and building damage thresholds. To present the animal bTBI data on a P-I graph for humans, the reported peak pressures needed to be scaled to humans, impulse values calculated, and impulse values scaled. Peak pressures were scaled using Jean et al.\u27s method, which accounts for all the structures of the head. Impulse values were estimated in two methods: Friedlander\u27s impulse equation and a proposed modification to the Friedlander\u27s impulse equation. The modification was needed as some animal testing was not subjected to shock waves with a steady decay, such as outside the end of a shock tube. Mass scaling was used to scale the reported time duration in the impulse calculation. The scaled peak pressure and impulse values were plotted on a P-I graph with the reported severity. The three severities did not overlap; thus, each severity had its own region on the P-I graph. The severity regions were overlaid with lung damage and eardrum rupture P-I curves. Seven correlations were found between the bTBI regions and the observable injuries. bTBIs are not a new phenomenon, but in the past other serious injuries were more prominent, due to body armor not attenuating the shock wave as effectively --Abstract, page iii

Common Asset Impact on Default Contagion

In this work we present a simulation study to show that a shock in a common asset can be very impactful to default contagion, and we extend some analytic concepts to this scenario with common assets. We use an inhomogeneous random graph to represent the banking network, and, based on the possible exposures between banks, we define a minimum amount of capital each bank must hold in order to make the system stable to a shock that affects only a few banks. Then, we consider the case when a shock hits all banks at the same time, making them weaker and some of them initially in default. We analyze the final fraction of banks in default and compare it with other cases when the shock hits only a small proportion of banks. We show that a common shock can cause severe damage to the system

Shocks and finite-time singularities in Hele-Shaw flow

Hele-Shaw flow at vanishing surface tension is ill-defined. In finite time, the flow develops cusp-like singularities. We show that the ill-defined problem admits a weak {\it dispersive} solution when singularities give rise to a graph of shock waves propagating in the viscous fluid. The graph of shocks grows and branches. Velocity and pressure jump across the shock. We formulate a few simple physical principles which single out the dispersive solution and interpret shocks as lines of decompressed fluid. We also formulate the dispersive weak solution in algebro-geometrical terms as an evolution of the Krichever-Boutroux complex curve. We study in detail the most generic (2,3) cusp singularity, which gives rise to an elementary branching event. This solution is self-similar and expressed in terms of elliptic functions.Comment: 24 pages, 11 figures; references added; figures change