Influence of thermal wall boundary condition on scalar statistics during flame-wall interaction of premixed combustion in turbulent boundary layers
Influence of thermal wall boundary condition on scalar statistics during flame-wall interaction of premixed combustion in turbulent boundary layers
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DOI：
10.1016/j.ijheatfluidflow.2021.108881
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发表时间：
2021-11-12
影响因子：
2.6
通讯作者：
Klein, Markus
中科院分区：
文献类型：
--
作者：
Ahmed, Umair;Chakraborty, Nilanjan;Klein, Markus
本文研究了湍流边界层中热壁边界条件对预混火焰与壁面相互作用过程中标量统计特性的影响。对充分发展的湍流边界层中火焰与化学惰性等温壁和绝热壁相互作用的两种不同流动构型进行了三维直接数值模拟。第一种配置是在湍流通道流中的V形火焰的斜壁相互作用（OWI），第二种配置代表在湍流边界层中的平面火焰的迎面相互作用（HOI）。这些模拟的非反应条件下的湍流代表基于摩擦速度的雷诺数Re-tau = 110，而燃烧特性代表大气条件下的化学计量的甲烷-空气混合物。已观察到的进展变量和无量纲温度的平均行为的差异的两种配置响应于不同的壁边界条件。平均标量方差的进展变量和温度和它们各自的标量耗散率进行了研究，它被发现的进展变量和温度的方差保持耦合在绝热壁的情况下，而这些量之间存在显着差异在等温壁条件下的壁附近的两种流动配置。在不同的热壁边界条件下，在两种流动配置中，FWI期间进展变量和温度的平均标量耗散率均向壁面减小，但在等温壁面条件的情况下，与无因次温度相比，观察到更高的无因次温度标量耗散率。进展变量的标量耗散率。进步变量和无量纲温度的平均湍流标量通量的行为表明，标量通量可以显示梯度和反梯度型行为取决于流动配置，也对火焰的接近壁。在V-火焰OWI的情况下，壁边界条件的选择有一个显着的影响的标量通量的行为，而在湍流边界层HOI的情况下，没有显着差异的标量通量观察到不同的壁边界条件。
The influence of thermal wall boundary conditions on the behaviour of scalar statistics during flame-wall interaction (FWI) of premixed flames within turbulent boundary layers has been investigated. Three-dimensional direct numerical simulations (DNS) of two different flow configurations for flames interacting with chemically inert isothermal as well as adiabatic walls in fully developed turbulent boundary layers have been performed. The first configuration is an oblique wall interaction (OWI) of a V-flame in a turbulent channel flow and the second configuration is representative of head-on interaction (HOI) of a planar flame in a turbulent boundary layer. The turbulence in the non-reacting conditions for these simulations is representative of a friction velocity based Reynolds number of Re-tau = 110 while the combustion characteristics are representative of stoichiometric methane-air mixture under atmospheric conditions. Differences in the mean behaviours of the progress variable and non-dimensional temperature have been observed for the two configurations in response to different wall boundary conditions. Mean scalar variance of the progress variable and temperature and their respective scalar dissipation rates have been investigated and it is found that the variances of the progress variable and temperature remain coupled in the case of adiabatic walls, while significant differences exist between these quantities in the vicinity of the wall under isothermal wall conditions for both flow configurations. The mean scalar dissipation rates of progress variable and temperature during FWI decrease towards the wall in both flow configurations under different thermal wall boundary conditions, but in the case of isothermal wall conditions a higher scalar dissipation rate for the non-dimensional temperature is observed when compared with the scalar dissipation rate for the progress variable. The behaviours of the mean turbulent scalar fluxes of progress variable and the non-dimensional temperature suggest that the scalar fluxes can show both gradient and countergradient type behaviour depending on the flow configuration and also on the proximity of the flame to the wall. In the case of V-flame OWI, the choice of the wall boundary condition has a significant influence on the behaviour of the scalar fluxes, whereas in the case of turbulent boundary layer HOI, no significant differences in the scalar fluxes are observed for different wall boundary conditions.