Strain rate and flame orientation statistics in the near-wall region for turbulent flame-wall interaction

Abstract

Flame-wall interaction (FWI) in premixed turbulent combustion has been analyzed based on a counter-flow like configuration at the statistically stationary state. For the present configuration, the two FWI sub-zones, i.e the influence zone and the quenching zone, can be quantified from the DNS results. Detailed analysis of the important quantities, such as the flame temperature, flame-wall distance, wall heat flux, flame curvature and dilatation (including the flame normal and tangential strain rates), and some orientation relations between the flame normal and the principal strain rate directions, have been reported, together with the physical explanations. All these statistical results are determined by the relative strengths of the wall heat flux, thermal expansion and the flame-turbulence interaction.

Computational Investigation of Weakly Turbulent Flame Kernel Growths in Iso-Octane Droplet Clouds in CVC Conditions

“…The reactive scalar gradient is less preferentially aligned with the compression direction e 3 and more preferentially aligned with the extensive direction e 1 in the flame, which leads to a negative TSI contribution in both cases 3D_R_CP_ST01 and 3D_R_CP_ST10. Such a rotation of the orientation vector in the vicinity of the flame has been previously reported in experimental and numerical studies conducted under different conditions [29,58,52,26]. To assess the physical processes that are responsible for this change of orientation, the budget of the vector n is considered in Fig.…”

“…Whatever the scalar is chemically-reactive (e.g., progress variable) or not (e.g., mixture fraction), its variance as well as the shape of its probability density function (PDF) are indeed settled, to a large extent, by the scalar dissipation rate (SDR), see for instance [15,16,17,18]. The SDR is the product of the scalar diffusivity with the square of the scalar gradient norm [19,20,21] and, the studies reported in references [21,22,23,24,25,26] excepted, it is noteworthy that there were quite few efforts directed towards its detailed analysis in turbulent reactive two-phase flows. Moreover, it should be emphasized that most of the seldom studies that have been conducted in this direction were focused on the direct effect of the additional source terms associated with the evaporation process, see for instance [23,24,25].…”

Assessment of Bray Moss Libby formulation for premixed flame-wall interaction within turbulent boundary layers: Influence of flow configuration

“…The physical phenomenon in the near wall region during FWI has also been investigated in statistically planar turbulent premixed flames impinging on a flat inert wall at different temperatures by Zhao et al [20][21][22] and for different fuel Lewis numbers by Konstantinou et al [23]. Recent experimental findings for V-flames interacting with cold walls [24][25][26] and transient headon quenching [27] have confirmed the DNS findings regarding the influence of the flame on turbulence and vice verca.…”

Vectorial structure of the near-wall premixed flame

“…a near wall flame front consists of two parts, the head-on flame part with n • N > 0 and the entrained flame part n • N < 0 with N being the unit wall normal vector. As discussed by Poinsot et al [5] and Zhao et al [9,10], the vortex pair, or if the local flow moves away or towards the wall, determines the evolution and wrinkling of the flame front. Figure 4 shows the joint PDF between the flame-wall distance and the velocity component u 1 at the left side of flame brush edge for the case 8T0.…”

“…It is found that the terms of the SDR transport equation at the quenching stage near the wall shows distinctly different contribution from that away from the wall. Recently Zhao et al [9,10] introduced a statistically stationary FWI configuration as shown in Fig. 1.…”