A mesoscopic modelling approach for direct numerical simulations of transition to turbulence in hypersonic flow with transpiration cooling

Abstract

A rescaling methodology is developed for high-fidelity, cost-efficient direct numerical simulations (DNS) of flow through porous media, modelled at mesoscopic scale, in a hypersonic freestream. The simulations consider a Mach 5 hypersonic flow over a flat plate with coolant injection from a porous layer with 42 % porosity. The porous layer is designed using a configuration studied in the

Multiscale analysis of thermomechanical stresses in double wall transpiration cooling systems for gas turbine blades

“…This literature has mainly dealt with either the aerothermal aspects of film cooling related to the flow of fluids around film holes to determine surface temperatures and heat conduction coefficients or mechanical aspects related to deformation and damage development, particularly around the film holes. Aerothermal studies have taken into account coolant-mainstream gas interactions [15,16], turbulence and vorticity production [17,18], crossflow orientation effects [19], and the effect of hole shape, spacing [19][20][21] and surface roughness [22]. The evaluation of mechanical performance general centres on prediction of damage development and failure under creep-fatigue conditions [23][24][25][26] informed by based on thermal-elastic stress analysis [27] and informed by thermomechanical fatigue and creep rupture experiments [25,26,28,29].…”

Turbulence Effect on Transpiration Cooling Effectiveness Over a Flat Plate in Hypersonic Flow and Sensitivity to Injection Parameters

“…In particular, a grid resolution requirement dependent on the friction-based Reynolds number is presented for both Δx+ and Δz+ in the work of Yang et al (2021), and our considered values of Δx+ and Δz+ are within the threshold values indicated in Yang et al (2021) for resolving 99 % of the wall shear-stress events at a calculated friction Reynolds number of Re = 325 , based on the 99 , within the downstream turbulent region. Simulations are carried out at the freestream Mach number M = 5 , temperature T * ∞ = 76.6 K and Reynolds number Re = 12600 , relative to the boundary-layer displacement thickness at the inlet, and for isothermal wall with wall temperature T * w = 290 K. The freestream and wall temperature conditions are the same as in the studies (Cerminara et al 2020(Cerminara et al , 2021, and are associated to the hypersonic wind-tunnel experiments of Hermann et al (2018). Periodic conditions are imposed at the side boundaries.…”

“…Air is considered as the coolant fluid, which is the same species as the freestream fluid. It is assumed that the coolant exits the pores at the same pressure conditions as the local flow on the surface, thus mimicking a case in which the pressure drop across the underneath porous medium corresponds to the difference between the reservoir pressure and the external (or environmental) pressure on the surface Cerminara et al (2020). Simulations have been run at three different values of the blowing ratio, i.e.…”

“…They found a reduction in the cooling effectiveness due to the turbulent transport. The studies of Cerminara et al (2020Cerminara et al ( , 2021 have found that transpiration cooling performs better then slot injection when transition to turbulence occurs, as the transition process of slot injection has been observed to produce a larger dispersion of coolant away from the wall. However, the mechanisms through which the parameters of the porous structure and the injection patterns affect the mixing and the associated fluid dynamics features of the turbulent boundary layer have not been investigated yet.…”

“…Moreover, rapid transition to turbulence is induced via application of an unsteady high-amplitude disturbance model upstream of the porous injection region, and the computational domain size is designed to accomodate a full transition process to a developed turbulent field at larger downstream distances from the injection region. The freestream conditions are the same as those considered in the works of Cerminara et al (2020Cerminara et al ( , 2021. The aim of the present study is to analyse the features of porous injection in a turbulent hypersonic boundary layer, with emphasis on the effects on the near-wall coolant concentration and the deficit in cooling effectiveness associated with a turbulent flow, as compared to a laminar flow case, as well as to analyse the solution sensitivity to important parameters of the porous injection model, namely blowing ratio and pore diameter.…”