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Table 2.

Spectral slope and the inferred Mach number for our different shock tube models.

Flat Turb Flat Turb
Theory Initial ℳ 2.00 2.00 3.00 3.00

Expected slope –3.33 –3.33 –2.5 –2.5

Low momenta Measured slope -3.36 –2.73 –2.49 -2.42

Implied ℳ 1.98 2.54 3.03 3.25

High momenta Measured slope –4.28 –3.50 –3.45 -3.35

Implied ℳ 2.03 3.01 3.15 3.54

Notes. Top two rows: Initial Mach number for each simulation and the expected slope calculated using Eq. (15). Middle two rows: Measured slope at low (10 < p < 103) momenta and the Mach number that one would infer using Eq. (14). Bottom two rows: As previous but for high momenta (104 < p < 105) and making the typical assumption that this slope is αe − 1. The tail of the Mach number distribution produces shallower slopes and breaks the αe − 1 assumption. These effects both lead to an overestimation of the peak Mach number in the shock.

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