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A mesoscopic modelling approach for direct numerical simulations of transition to turbulence in hypersonic flow with transpiration cooling
International Journal of Heat and Fluid Flow ( IF 2.6 ) Pub Date : 2020-12-01 , DOI: 10.1016/j.ijheatfluidflow.2020.108732
Adriano Cerminara , Ralf Deiterding , Neil Sandham

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 literature, consisting of a staggered arrangement of cylinder/sphere elements. A characteristic Reynolds number Re c of the flow in a pore cell unit is first used to impose aerodynamic similarity between different porous layers with the same porosity, ∊ , but different pore size. A relation between the pressure drop and the Reynolds number is derived to allow a controlled rescaling of the pore size from the realistic micrometre scales to higher and more affordable scales. Results of simulations carried out for higher cylinder diameters, namely 24 μm, 48 μm and 96 μm, demonstrate that an equivalent Darcy-Forchheimer behaviour to the reference experimental microstructure is obtained at the different pore sizes. The approach of a porous layer with staggered spheres is applied to a 3D domain case of porous injection in the Darcy limit over a flat plate, to study the transition mechanism and the associated cooling performance, in comparison with a reference case of slot injection. Results of the direct numerical simulations show that porous injection in an unstable boundary layer leads to a more rapid transition process, compared to slot injection. On the other hand, the mixing of coolant within the boundary layer is enhanced in the porous injection case, both in the immediate outer region of the porous layer and in the turbulent region. This has the beneficial effect of increasing the cooling performance by reducing the temperature near the wall, which provides a higher cooling effectiveness, compared to the slot injection case, even with an earlier transition to turbulence.

中文翻译:

具有蒸腾冷却的高超声速流向湍流过渡的直接数值模拟的细观建模方法

摘要 开发了一种重新缩放方法,用于高保真、经济高效的直接数值模拟 (DNS),在高超声速自由流中以细观尺度建模通过多孔介质的流动。模拟考虑了马赫数为 5 的高超声速流过平板,冷却剂从孔隙率 42% 的多孔层注入。多孔层是使用文献中研究的配置设计的,由圆柱/球体元素的交错排列组成。孔隙单元中流动的特征雷诺数 Re c 首先用于在具有相同孔隙率 ∊ 但不同孔径的不同多孔层之间施加空气动力学相似性。推导出压降和雷诺数之间的关系,以允许将孔径从实际微米级可控地重新缩放到更高和更实惠的级。对更高圆柱直径(即 24 μm、48 μm 和 96 μm)进行的模拟结果表明,在不同孔径下获得了与参考实验微观结构等效的 Darcy-Forchheimer 行为。将具有交错球体的多孔层的方法应用于平板上达西极限下多孔注射的 3D 域情况,以研究过渡机制和相关的冷却性能,并与槽注射的参考情况进行比较。直接数值模拟的结果表明,不稳定边界层中的多孔注入导致更快速的转变过程,与槽注入相比。另一方面,在多孔注入情况下,在多孔层的直接外部区域和湍流区域中,边界层内冷却剂的混合得到增强。这具有通过降低壁附近温度来提高冷却性能的有益效果,与狭缝喷射情况相比,即使较早过渡到湍流,这也提供了更高的冷却效率。
更新日期:2020-12-01
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