Abstract
The Rankine-Hugoniot equations presented in Chap. 3 include the equations for the calculation of the reflected pressure, given the incident overpressure and the ambient conditions. The reflected overpressure divided by the incident overpressure is the reflection factor. The R-H reflected overpressure equation can only be used when the incident shock strikes a plane surface at an incident angle of 90°, that is, when the vector for the shock velocity is perpendicular to the reflecting surface. Even in this case, the reflection factor is a function of the gamma of the gas. Brode (1970) gives a curve for the reflection factor for air as a function of the incident overpressure. Figure 13.1 gives the reflection factor as a function of incident overpressure for constant gamma gasses and for air as the gamma changes with overpressure. The dashed lines represent gasses from monatomic, with gamma of 5/3, to partially ionized gasses with gamma near 1.17. This can be confirmed by referring to Fig. 3.3 which shows that the value of gamma for sea level density air approaches a value of 1.17 at an internal energy density of 2.e11 ergs/gm. The temperature at this energy density is approximately 9000 K.
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Needham, C.E. (2018). Blast Wave Reflections. In: Blast Waves. Shock Wave and High Pressure Phenomena. Springer, Cham. https://doi.org/10.1007/978-3-319-65382-2_13
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