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As far as I know, the total pressure changes across a shock wave. How is this possible if you are in the atmosphere and atmospheric pressure isn't changing? Is energy lost due to entropy in generated through a shock wave, and therefore a loss of pressure occurs?

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  • $\begingroup$ I answered under the assumption that you were confused about the source of the pressure change across a shock. If that is what you were asking, then try rewording the question accordingly. $\endgroup$ – honeste_vivere Dec 13 '15 at 1:00
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The scalar pressure changes across a shock wave in a collisional fluid because of the conservation of momentum and energy flux. This is one of the conservation equations in the Rankine-Hugoniot relations which govern the thermodynamics of shock waves.

The entropy increases because the change in bulk kinetic energy across the shock wave is irreversibly converted into random kinetic energy (i.e., heat).

Note that irreversibility is required for a shock wave to form in the first place. Without irreversibility, a nonlinearly steepening wave would break kind of like water waves do on a windy day.

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