The statistical method for describing the intermittency coefficient in the region of laminar–turbulent boundary layer transition at the low level of external perturbations is proposed. The method is based on the assumption that turbulence develops when the velocity deviates locally in space and time from the mean by a threshold value. The analytical formulas are obtained for the frequency of occurrence of the coherent structures (turbulent spots and wedges) and for the intermittency coefficient or the mean fraction of the surface area covered by them in the case of two basic scenarios of transition, namely, the enhancement of steady crossflow instability vortices on the swept wing and the Tollmien–Schlichting waves.

中文翻译：

---

低湍流度下过渡区间断的统计描述

提出了描述低水平外部扰动下层流-湍流边界层过渡区域间断系数的统计方法。该方法基于这样的假设：当速度在空间和时间上局部偏离平均值一个阈值时，就会产生湍流。获得了相干结构（湍流点和楔形）出现频率和间歇系数或它们覆盖的表面积的平均分数在两种基本过渡情况下的解析公式，即增强后掠翼上的稳定横流不稳定涡和 Tollmien-Schlichting 波。