Journal ArticleDOI
Turbulent flame–wall interaction: a direct numerical simulation study
TLDR
In this article, the effects of the wall turbulent boundary layer (i) on the structure of a hydrogen-air premixed flame, (ii) on its near-wall propagation characteristics and (iii) on spatial and temporal patterns of the convective wall heat flux are investigated.Abstract:
A turbulent flame–wall interaction (FWI) configuration is studied using three-dimensional direct numerical simulation (DNS) and detailed chemical kinetics. The simulations are used to investigate the effects of the wall turbulent boundary layer (i) on the structure of a hydrogen–air premixed flame, (ii) on its near-wall propagation characteristics and (iii) on the spatial and temporal patterns of the convective wall heat flux. Results show that the local flame thickness and propagation speed vary between the core flow and the boundary layer, resulting in a regime change from flamelet near the channel centreline to a thickened flame at the wall. This finding has strong implications for the modelling of turbulent combustion using Reynolds-averaged Navier–Stokes or large-eddy simulation techniques. Moreover, the DNS results suggest that the near-wall coherent turbulent structures play an important role on the convective wall heat transfer by pushing the hot reactive zone towards the cold solid surface. At the wall, exothermic radical recombination reactions become important, and are responsible for approximately 70% of the overall heat release rate at the wall. Spectral analysis of the convective wall heat flux provides an unambiguous picture of its spatial and temporal patterns, previously unobserved, that is directly related to the spatial and temporal characteristic scalings of the coherent near-wall turbulent structures.read more
Citations
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Journal ArticleDOI
Large eddy simulation with modeled wall-stress: recent progress and future directions
TL;DR: In this article, the authors provide a brief introduction to the near-wall problem of LES and how it can be solved through modeling of the near wall turbulence, and the distinctions and key differences between different approaches are emphasized, both in terms of fidelity (LES, wall-modeled LES, and DES) and in the terms of different wall modelled LES approaches (hybrid LES/RANS and wall-stress-models).
Journal ArticleDOI
Advanced laser diagnostics for an improved understanding of premixed flame-wall interactions
Andreas Dreizler,Benjamin Böhm +1 more
TL;DR: The role of laser diagnostics in combustion science and technology is discussed in this article, where the focus is on using optical diagnostics to probe thermal, fluidic, and chemical properties of head-on and sidewall quenching.
Journal ArticleDOI
Direct numerical simulation of premixed flame boundary layer flashback in turbulent channel flow
TL;DR: In this article, the authors investigate the transient upstream propagation of premixed hydrogen-air flames in the boundary layer of a fully developed turbulent channel flow and show that the leading edges of the upstream-propagating premixed flame are always located in the near-wall region of the channel and assume the shape of several smooth, curved bulges propagating upstream side by side in the spanwise direction and convex towards the reactant side of the flame.
Journal ArticleDOI
The anchoring mechanism of a bluff-body stabilized laminar premixed flame
Kushal S. Kedia,Ahmed F. Ghoniem +1 more
TL;DR: In this paper, the authors investigate the mechanism of the laminar premixed flame anchoring near a heat-conducting bluff-body and show that a shear-layer stabilized flame anchors at an immediate downstream location near the bluff body where favorable ignition conditions are established; a region associated with (1) a sufficiently high temperature impacted by the conjugate heat exchange between the heat conductance and the hot reacting flow and (2) locally maximum stoichiometry characterized by the preferential diffusion effects.
Journal ArticleDOI
Advances and challenges in modeling high-speed turbulent combustion in propulsion systems
TL;DR: In this paper, the authors address the problems encountered when modeling high-speed combustion, or in other words, what are the problems of turbulent-combustion modeling? Do such interactions need modeling? What are the challenges when going from modeling low-speed-to-high-speed combustions problems?
References
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Journal ArticleDOI
Turbulence statistics in fully developed channel flow at low reynolds number
TL;DR: In this article, a direct numerical simulation of a turbulent channel flow is performed, where the unsteady Navier-Stokes equations are solved numerically at a Reynolds number of 3300, based on the mean centerline velocity and channel half-width, with about 4 million grid points.
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Boundary conditions for direct simulations of compressible viscous flows
TL;DR: In this article, a boundary condition formulation for the Navier-Stokes equations is proposed, which is compatible with non-disjoint algorithms applicable to direct simulations of turbulent flows.
Journal ArticleDOI
Direct numerical simulation of turbulent channel flow up to Reτ=590
TL;DR: In this paper, numerical simulations of fully developed turbulent channel flow at three Reynolds numbers up to Reτ=590 were reported, and it was noted that the higher Reynolds number simulations exhibit fewer low Reynolds number effects than previous simulations at Reτ = 180.