Numerical Analysis of Heat Flux Reduction by Transpiration Cooling in Laminar Hypersonic Flow

Transpiration cooling is an active thermal protection system in which a coolant is injected through a porous wall into the external boundary layer, where it convects heat from the surface and establishes an insulating film that can also reduce oxidation.Hypersonic vehicles experience extreme aerodynamic heating during ascent, cruise, and re-entry, and conventional thermal protection systems are often non-reusable.Existing studies primarily focus on near-injector behavior and turbulent flows, while research on downstream laminar performance is lacking.This work addresses this gap by numerically simulating the reduction in post-injection heat flux.A steady-state two-dimensional CFD simulation of ideal-gas air at Mach 7 over an isothermal flat plate with a mass-flow inlet is performed in ANSYS Fluent 2025 R1 using a viscous, laminar, pressure-based solver, for six blowing ratios.The uncooled case matches the Eckert reference-enthalpy correlation.Coolant injection reduces wall heat flux downstream, with the thermal effectiveness decaying as the coolant mixes with the freestream flow.At 200 mm downstream, thermal effectiveness varies from 6% to 78% with the blowing ratio.The author proposes a modified correlation.This study supports rapid thermal protection design analysis and identifies areas requiring further validation.