时间步预算可视化

比较对流 CFL、声学 CFL 与扩散 Fourier 限制，找出当前时间步瓶颈。

visual calculator数值与稳定性

先看流动形态，再相信数字。

该工具把 CFD 设置转换为工况、尺度和主导效应提示。调节下方计算器，观察动态图与计算结果如何一起变化。

输入尺度

模型

判断

time stepCFLFourierexplicit solver

公式

KaTeX rendered

\begin{aligned}\text{dt\_max = min(C dx/U}\\[0.35em]\text{C\_a dx/(a+U)}\\[0.35em]\text{Fo dx\^{}2/nu)}\end{aligned}

ASCII source

dt_max = min(C dx/U, C_a dx/(a+U), Fo dx^2/nu)

dt current (s)dx min (m)|U|max (m/s)sound speed a (m/s)nu or alpha (m^2/s)CFL maxacoustic CFL maxFo max

limiting dt (s)

7.792e-6

current / limit

1283.3%

limiting physics

acoustic CFL

advective dt (s)

8.889e-5

acoustic dt (s)

7.792e-6

diffusion dt (s)

0.4167

current CFL

0.9000

current Fo

6.000e-5

For compressible explicit solvers, acoustic speed often dominates. For viscous DNS/LES near walls, the diffusion limit can become the smallest budget.

time step CFL Fourier explicit solver