Pressure along the tunnel
MOC
HLLC
train
area / shafts
Pressure at the moving train · external and sealed cabin
external HLLC
cabin HLLC
external MOC
cabin MOC
Cabin follows dp/dt=(p_ext−p_cabin)/τ sampled at the train's live position. Worst rolling-window Δp of these signals feeds the compliance matrix.
Air flow velocity along the tunnelpositive → toward exit portal
MOC
HLLC
train
Induced air velocity (piston flow ahead of the train, annulus backflow alongside it, and the oscillating column after portal reflections).
Space–time wave field (x–t)
Every wave the run produces, in one frame: time runs downward, distance across. Diagonal bands are waves; the reversal of colour at a portal is the inverted reflection; the pink line is the train.
Reverberation decay · run until the wave dies
Peak |Δp| envelope in the bore on a log axis. The run continues until the field decays to 3% of its peak, then stops automatically.
Compliance matrix · high-speed rail pressure codes
Health/aural limits are graded on the raw external signature (sealing ignored, as the codes require); comfort limits on the sealed-cabin signal. SOLVERS DIFFER flags a design point where the two methods reach opposite verdicts.