Ia型超新星：用线性涡模型计算湍流火焰
Type Ia Supernova: Calculations of Turbulent Flames Using the Linear Eddy Model
摘要：
探讨了Ia型超新星中碳燃烧火焰与柯尔莫哥洛夫湍流相互作用的性质。利用Kerstein（1991）的线性涡模型进行的一维计算阐明了湍流燃烧的三种状态。在最简单的情况下，大尺度湍流使薄层火焰发生折叠和变形，产生总燃烧率近似为积分尺度上湍流脉动速度U_L的火焰刷。这是超新星爆炸开始的区域，也是爆炸前大部分燃烧发生的区域。随着密度的下降，湍流开始撕裂单个火焰，使更广泛的结构移动得更快。在很短的时间内，这些湍流火焰与它们的间距相比仍然很窄，并且以U_L的总速度移动的火焰刷的概念仍然有效。然而，由其周转时间等于其燃烧时间的条件给出的单个火焰的典型宽度随着密度的下降而继续增加。最终，几乎与积分尺度本身一样大的混合区域瞬时形成。在这一点上，可以发生向爆炸的过渡。对这种转变的条件进行了数值研究，估计在1 × 10**7 g/cm**3附近的密度下，如果积分尺度上的湍流速度超过约15%音速，就会发生这种转变。计算实例显示了实际发生爆炸的细节。
英文摘要：
The nature of carbon burning flames in Type Ia supernovae is explored as they interact with Kolmogorov turbulence. One-dimensional calculations using the Linear Eddy Model of Kerstein (1991) elucidate three regimes of turbulent burning. In the simplest case, large scale turbulence folds and deforms thin laminar flamelets to produce a flame brush with a total burning rate given approximately by the speed of turbulent fluctuations on the integral scale, U_L. This is the regime where the supernova explosion begins and where most of its pre-detonation burning occurs. As the density declines, turbulence starts to tear the individual flamelets, making broader structures that move faster. For a brief time, these turbulent flamelets are still narrow compared to their spacing and the concept of a flame brush moving with an overall speed of U_L remains valid. However, the typical width of the individual flamelets, which is given by the condition that their turnover time equals their burning time, continues to increase as the density declines. Eventually, mixed regions almost as large as the integral scale itself are transiently formed. At that point, a transition to detonation can occur. The conditions for such a transition are explored numerically and it is estimated that the transition will occur for densities near 1 x 10**7 g/cm**3, provided the turbulent speed on the integral scale exceeds about 15% sonic. An example calculation shows the details of a detonation actually developing.
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