Shock Waves in Three-Dimensional Elastic Solids.

In this paper some characteristics of non-steady, compressible, flow are explored, including compression and expansion wave interactions and creation. The work to be presented herein is a Computational Fluid Dynamics investigation of the complex fluid phenomena that occur inside three-dimensional region, specifically with regard to the structure of the oblique shock waves, the reflected shock waves and the interactions of the shock waves. The flow is so complex that there exist oblique shock waves, expansion fans, slip surfaces, and shock wave interactions and reflections. The flow is non-steady, turbulent, viscous, compressible, and high-speed supersonic. The work to be presented herein is a Computational Fluid Dynamics analysis of flow over a 15-degree angle double wedge for a compressible air, with spin angle of 10-degree and Mach number of 2.5. The problem to be solved involves formation of shock waves, expansion fans and slip surfaces, so that the general characteristics of supersonic flow are explored through this problem. Shock waves and slip surfaces are discontinuities in fluid mechanics problems. It is essential to evaluate the ability of numerical technique that can solve problems in which shocks and contact surfaces occur. In particular it is necessary to understand the details of developing a mesh that will allow resolution of these discontinuities. Results including contour plots of pressure, temperature, and Mach number will show that CFD is capable of predicting accurate results and is also able to capture the discontinuities in the flow, e.g., the oblique shock waves and the slip surfaces. Through this computational analysis, a better interpretation of the physical phenomenon of the three-dimensional shock waves interaction and reflection can be achieved.

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Evaluation of Intracranial Pressure Response in Rats Exposed to Complex Shock Waves

ASME 2012 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2012-80265 ◽

2012 ◽

Author(s):

Alessandra Dal Cengio Leonardi ◽

Nickolas Keane ◽

Cynthia Bir ◽

Pamela VandeVord

Keyword(s):

Intracranial Pressure ◽

Shock Waves ◽

Blast Wave ◽

Preliminary Investigation ◽

Free Field ◽

Three Dimensional ◽

Head Orientation ◽

Reflected Shock ◽

Complex Wave ◽

The Individual

Studies on blast neurotrauma have focused on investigating the effects of exposure to free-field blast representing the simplest form of blast threat scenario without considering any reflecting surfaces. However, in reality personnel are often located within enclosures or nearby reflecting walls causing a complex blast environment, that is, involving shock reflections and/or compound waves from different directions. In fact, when a blast wave interacts with nearby structures, reflected shock waves are generated and complex three-dimensional shock waves are formed. Complex shock wave overpressure-time traces are significantly different from free-field profiles because reflections can cause super-positioning of shock waves resulting in increased pressure magnitudes and multiple pressure peaks. Very importantly, the shocks arrive from different directions which would invoke a different biomechanical response than a one-dimensional exposure. It has been reported that in complex wave environments, the extent of the injuries becomes a function of the location related to the surrounding structures rather than a function of the distance from the center of the explosion, as it is for free-field conditions (Yelverton et al. 1993; Mayorga 1997; Stuhmiller 1997). Furthermore, the resulting injuries when the individual is in confined spaces are noted to be more severe (Yelverton et al. 1993; Leibovici et al. 1996). The purpose of this study was to design a complex wave testing system and perform a preliminary investigation of the intracranial pressure (ICP) response of rats exposed to a complex blast wave environment. Furthermore, we explored the effects of head orientation in the same environment.

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