The pressure immediately behind a shock wave, denoted as , refers to the pressure of a fluid right after it has passed through the shock wave. In the context of shock waves, represents the pressure on the side of the shock wave where the fluid has undergone a rapid and significant increase in pressure due to compression and other thermodynamic effects. When a fluid encounters a shock wave, it experiences a sudden change in its properties, including pressure, temperature, density, and velocity. The pressure immediately behind the shock wave is higher compared to the pressure upstream of the shock wave (), which is the pressure on the side from which the fluid is approaching the shock wave.
- is the pressure immediately behind the shock wave.
- is the pressure upstream (ahead) of the shock wave.
- is the pressure ratio across the shock wave.