Investigation of Partial-Catalytic Boundary Conditions for High-Speed Flows

CFD was used to quantify the differences in the integrated wall heating caused by non-catalytic vs. fully-catalytic boundary conditions over a 2D-wedge model for a range of Mach numbers (7 < Mach < 10) and altitudes (25km < Alt. < 45km). For Mach numbers between 8.5 and 10, results showed measurable differences between non-catalytic and fully-catalytic models on the integrated wall heating (> 4%), independent of altitude, and as high as ~40% for Mach 10 at an altitude of 45km. Results for a partially-catalytic model showed an exponential dependency of the wall heating on the recombination coefficient of atomic oxygen (γO) for the regime in question, as (γO) approaches one, a partially-catalytic model exponentially approaches the fully-catalytic model. This study provides two revelations: (γO) must be of the order of (~1e-3) to produce a significantly different solution in-between both extremes (non and fully-catalytic), and simulations in which (γi) are not known for all i-species expected to recombined should use a fully-catalytic model since it provides the most conservative prediction of wall heating.