Direct numerical simulations of coolant injection through a porous layer for transpiration cooling in hypersonic flow

Abstract

The present work describes latest advancements in the context of high-fidelity numerical simulations of flow through porous media in a hypersonic freestream. The aim of this work is to find an appropriate solution to the challenging requirement of accurately resolving complex multiscale flow features combined with minimum computational cost, as well as to design a methodology that allows predictive capabilities for the aerothermal design of new-generation thermal protection systems (TPS) for hypersonic vehicles. The requirement of an accurate and reliable solution which captures the main physical insights of the flow is particularly strict when dealing with hypervelocity flows, because of the dramatic consequences that aerodynamic heating and transition to turbulence have on the vehicle structure integrity in this flow regime. A numerical study is presented which investigates, through direct numerical simulation (DNS) of the Navier-Stokes equations, the main characteristics of a hypersonic flow at Mach 5 over a flat plate with coolant injection provided from a layer of distributed porosity that mimics the properties of a real porous material sample used in a ground-test experiment. The numerical simulations are performed using a 6th-order hybrid WENO-central scheme, with a structured adaptive mesh refinement (SAMR) technique that provides adequate grid resolution in the very small scales of the porous region. A regular arrangement of staggered cylinders is considered to model the porous structure, and the correlation between pressure drop and flow rate across the porous layer is simulated for different cylinder diameters and at the same experimental flow conditions. In particular, based on a former computational study available in the literature, a multiscale numerical methodology is developed and assessed for inner particle diameters from 12 micrometre up to 96 micrometre, which allows an equivalent Darcy-Forchheimer behaviour relative to a real small-scale porous sample to be replicated by a porous layer with significantly higher pore scales.

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Identifiers

ORCID for Ralf Deiterding: orcid.org/0000-0003-4776-8183

ORCID for Neil Sandham: orcid.org/0000-0002-5107-0944

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