A TWO-DECK BOUNDARY LAYER MODEL OF THE FLOW OVER AN ABLATING (AND/OR TRANSPIRING) SURFACE IS PROPOSED IN ORDER TO COMPUTE THE SURFACE ROUGHNESS AND TEMPERATURE DISTRIBUTION IN THE WALL AND FLOW FOR A GIVEN SET OF WALL AND FREESTREAM CONDITIONS.

A TWO-DECK BOUNDARY LAYER MODEL OF THE FLOW OVER AN ABLATING (AND/OR TRANSPIRING) SURFACE IS PROPOSED IN ORDER TO COMPUTE THE SURFACE ROUGHNESS AND TEMPERATURE DISTRIBUTION IN THE WALL AND FLOW FOR A GIVEN SET OF WALL AND FREESTREAM CONDITIONS. THE OUTER FLOW OF THE TWO-DECK MODEL RESEMBLES A CONVENTIONAL BOUNDARY LAYER WHICH SLIPS OVER A PERMEABLE SURFACE. THE INNER FLOW IS A ROUGHNESS-DOMINATED FILM-LIKE FLOW WHICH IS MATCHED TO THE OUTER FLOW AT THE LEVEL WHERE LATERAL SPATIAL VARIATIONS DUE TO ROUGHNESS HAVE "MIXED-OUT". THE INNER FLOW IS COMPUTED BY LOCALLY SPATIALLY-AVERAGING (IN HORIZONTAL PLANES AT EACH VERTICAL LOCATION) WITH A SCALE LARGE RELATIVE TO THE ROUGHNESS YET SMALL RELATIVE TO THE BOUNDARY LAYER GROWTH RATE. AS A RESULT, ANALYTICAL PARAMETERS ARE DEVELOPED WHICH CHARACTERIZED THE ROUGHNESS AND THE INNER-OUTER INTERFACE LOCATION. THE SURFACE ROUGHNESS, MASS TRANSFER, SKIN FRICTION AND HEAT TRANSFER ARE MODELED WITH SPATIAL/TEMPORAL NON-EQUILIBRIUM AND NON-LINEARITY FORMULATIONS. THIS ALLOWS THE MODEL TO BE USED TO ASSESS THE OVERALL STABILITY OF THE ABLATION PROCESS TO A LOCALIZED PERTURBATION IN WALL ROUGHNESS. TURBINES OPERATED AS JET ENGINES, TURBOFANS OR SHAFT POWER SPLIT THE FLOW INTO COMBUSTOR AND DETONATION DUCT