Inversion learning of turbulent thermal diffusion for film cooling

Zhang, Zhen; Mao, Yinbo; Chen, Ziyu; Yuan, Xin

doi:10.1063/5.0084237

Cited by 8 publications

(1 citation statement)

References 24 publications

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“…CFD can predict the right trend sometimes, and the CFD-based optimization improves the performance remarkably. However, experiment validation is always necessary, because sometimes the numerical and experimental trends are different, which is mainly caused by the insufficient turbulence mixing of the existing RANS models [ 17 ].…”

Section: Introductionmentioning

confidence: 99%

Optimization of the Double-Expansion Film-Cooling Hole Using CFD

Zhang

Chen

et al. 2023

Entropy

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Film cooling is a major cooling technique used in modern gas turbines and air engines. The geometry of film-cooling holes is the fundamental aspect affecting the cooling performance. In this paper, a new cooling configuration called the double-expansion film-cooling hole has been put forward, which yields better performance than the widely used shaped holes and is easy to manufacture. The double-expansion holes at inclination angles of α=30∘, 45∘, and 60∘ are optimized using the genetic algorithm and the Kriging surrogate model, which is trained by CFD data randomly sampled using the Latin hypercube method. The numerically optimized double-expansion holes at different inclination angles were experimentally evaluated and compared with the optimized single-expansion laid-back fan-shaped holes, and the optimized double-expansion hole at α=30∘ was manually modified based on experiment results. Compared with the optimal single-expansion holes, the area-averaged cooling effectiveness of the double-expansion holes was increased by 34.5% at α=30∘, by 27.8% at α=45∘, and basically the same at α=60∘, showing the benefit of the double-expansion concept. The loss mechanism of film cooling was also analyzed in the perspective of the entropy generation rate, showing the optimal double-expansion holes have 21% less loss compared to a baseline narrow single-expansion hole. It was also found that CFD sometimes predicts a different trend from the experiment in optimization, and the experimental validation is necessary.

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Section: Introductionmentioning

confidence: 99%

Optimization of the Double-Expansion Film-Cooling Hole Using CFD

Zhang

Chen

et al. 2023

Entropy

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Direct numerical simulation of the 7-7-7 film cooling at a range of compound angles

Bin,

Yang

2024

International Journal of Heat and Mass Transfer

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On the origin of counter-gradient transport in turbulent scalar flux: physics interpretation and adjoint data assimilation

Li,

Zhou,

Sung

et al. 2024

J. Fluid Mech.

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The present study offers a twofold contribution on counter-gradient transport (CGT) of turbulent scalar flux. First, by examining turbulent scalar mixing through synchronized particle image velocimetry and planar laser-induced fluorescence on an inclined jet in cross-flow, we clarify the previously unexplained phenomenon of CGT, revealing key flow structures, their spatial distribution and modelling implications. Statistical analysis identifies two distinct CGT regions: local cross-gradient transport in the windward shear layer and non-local effects near the wall after injection. These behaviours are driven by specific flow structures, namely Kelvin–Helmholtz vortices (local) and wake vortices (non-local), suggesting that scalar flux can be decomposed into a gradient-type term for gradient diffusion and a term for large-eddy stirring. Second, we propose a new approach for reconstruction of turbulent mean flow and scalar fields using continuous adjoint data assimilation (DA). By rectifying model-form errors through anisotropic correction under observational constraints, our DA model minimizes discrepancies between experimental measurements and numerical predictions. As expected, the introduced forcing term effectively identifies regions where traditional models fall short, particularly in the jet centreline and near-wall regions, thereby enhancing the accuracy of the mean scalar field. These enhancements occur not only within the observation region but also in unseen regions, underscoring present DA approach's reliability and practicality for reproducing mean flow behaviours from limited data. These findings lay a solid foundation for adjoint-based model-consistent data-driven methods, offering promising potential for accurately predicting complex flow scenarios like film cooling.

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Inversion learning of turbulent thermal diffusion for film cooling

Cited by 8 publications

References 24 publications

Optimization of the Double-Expansion Film-Cooling Hole Using CFD

Optimization of the Double-Expansion Film-Cooling Hole Using CFD

Direct numerical simulation of the 7-7-7 film cooling at a range of compound angles

On the origin of counter-gradient transport in turbulent scalar flux: physics interpretation and adjoint data assimilation

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