Supercritical tube flow
= Supercritical tube flow
{title2=$u>c$}
A positive <collapsible tube flow> is supercritical when both <characteristic speeds> $u\pm c$ are positive relative to the wall. Information then propagates downstream on both branches. For a quadratic pressure-area law and fixed dimensionless flux $q$, the condition is $A/A_0<\sqrt q$.