发表机构
Korea Advanced Institute of Science and Technology（韩国科学技术院）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究用G方程框架分析预混狭缝火焰在轴向-横向联合激励下的非线性运动学，发现平均位移主导FDF非线性饱和，并提出了统一理论模型及斯特劳哈尔数修正方法。
AI 中文摘要
本研究利用二维G方程水平集框架，研究了预混狭缝火焰的非线性运动学。结果表明，联合激励在火焰描述函数（FDF）中引发非线性饱和，其特征为早期增益平坦化和相位提前下降，且这些现象随横向激励幅值的增大而加剧。运动学分析揭示，这种几何非线性表现为时间平均火焰高度（定义为平均位移）的减小。在准稳态极限下，通过多元渐近展开对平均位移进行了解析量化，其中四阶项成功捕捉了高幅值下的饱和机制。通过引入一个考虑横向主导性的缩放参数，紧凑极限下平均位移的频率相关衰减塌缩到单一主曲线上，从而推导出一个统一的理论模型，该模型将这一渐近响应与二阶低通滤波器相结合。此外，由于平均位移减小了火焰的物理范围，它改变了褶皱传播时间。使用实测平均位移修正斯特劳哈尔数后，分散的非线性FDF曲线塌缩到线性理论预测上。该分析进一步扩展到以有限速度传播的扰动，对此线性传递函数被解析推导，且用实测平均位移的修正继续使非线性FDF塌缩。这些发现确立了在多维激励下非线性FDF行为从根本上受运动学平均位移的支配，为将几何非线性与湍流火焰中的其他热扩散或流体动力学不稳定性解耦提供了理论基线。
英文摘要
This study investigates the nonlinear kinematics of a premixed slit flame using a two-dimensional $G$-equation level-set framework. Results show that combined forcing induces nonlinear saturation in the FDF, characterized by early gain flattening and premature phase drops, which intensify with the transverse forcing amplitude. Kinematic analysis reveals that this geometric nonlinearity manifests as a reduction in the time-averaged flame height, defined as the mean shift. In the quasi-steady limit, this mean shift is analytically quantified via a multivariate asymptotic expansion, where fourth-order terms successfully capture the saturation mechanism at elevated amplitudes. By introducing a scaling parameter to account for transverse dominance, the frequency-dependent decay of the mean shift in the compact limit collapses onto a single master curve, enabling the derivation of a unified theoretical model that integrates this asymptotic response with a second-order low-pass filter. Furthermore, because the mean shift reduces the physical extent of the flame, it alters the wrinkle propagation time. Correcting the Strouhal number using the measured mean shift collapses the dispersed nonlinear FDF curves onto the linear theory prediction. The analysis is further extended to disturbances convected at a finite speed, for which the linear transfer function is derived analytically and the correction with the measured mean shift continues to collapse the nonlinear FDF. These findings establish that the nonlinear FDF behavior under multidimensional forcing is fundamentally governed by the kinematic mean shift, providing a theoretical baseline for decoupling geometric nonlinearities from other thermo-diffusive or hydrodynamic instabilities in turbulent flames.
Comments16 pages, 16 figures. Accepted for publication in Combustion and Flame
Journal refCombustion and Flame 294 (2026) 115317
DOI：10.1016/j.combustflame.2026.115317
