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Run 145 outlet-pressure selection

Operating-point target

NASA-CR-168015 reports Run 145 (code 4512) with an exit Mach number of M2 = 0.90. NASA defines this exit Mach from measured inlet total pressure and average measured exit-plane static pressure, and the facility used back-pressure control to set the exit-Mach condition. Table IX does not tabulate the corresponding Run 145 exit static pressure.

Primary source: Hylton et al., NASA-CR-168015 (1983), Test Conditions section and Table IX, report pp. 28–30.

The Fluent quantity used for the operating-point adjustment is different: the saved fine_mach_outlet report is a surface mass-weighted average of the local outlet Mach field. I therefore use the two values only to match the nominal operating point; outlet Mach is not treated as an independent validation metric.

Pressure adjustment

The first second-order calculation used a provisional outlet static pressure of 241200 Pa and gave a Fluent mass-weighted outlet Mach of 0.88064076.

I used a local isentropic pressure-ratio correction to estimate the pressure needed for a nominal target Mach of 0.90:

p_new = p_old * [
    (1 + (gamma - 1)/2 * M_target^2)
    / (1 + (gamma - 1)/2 * M_old^2)
]^(-gamma/(gamma - 1))

with

p_old    = 241200 Pa
M_old    = 0.88064076
M_target = 0.90000000
gamma    = 1.4

which gives

p_new = 236228.236 Pa

I rounded that estimate to 236200 Pa for the next Fluent continuation. The subsequent run gave a mass-weighted outlet Mach of 0.89951531. The released fine-grid SST baseline keeps the same 236200 Pa boundary condition and gives Mout = 0.90129444.

Stage Outlet static pressure Fluent mass-weighted outlet Mach
Provisional second-order point 241200 Pa 0.88064076
Isentropic estimate 236228.236 Pa n/a (estimate only)
Applied rounded setting 236200 Pa 0.89951531
Released fine SST baseline 236200 Pa 0.90129444

236200 Pa was therefore retained as the pressure-outlet boundary condition for the Run 145 operating point. Wall-temperature and HTC measurements were not used to choose it.

The machine-readable history is in ../references/model_inputs/run145_outlet_pressure_selection.csv.