open TELEMAC-MASCARET The mathematically superior suite of solvers

Hi,

As i am aware of the formula for CFL is (u * dt)/dx

i wish to know,
How is the constant dx being calculated in unstructured (triangle) mesh ?





Thanks
Sathya

The constant dx is computed is SUBROUTINE HLOC (in bief library), and corresponds to the variable DTHAUT.
The formula used to compute dx for each node :

dx = AREA around node / SUM of (directly connected) segment LENGTHS

There is an anwser in the topic "Courant number" at the post #12138

Hope it helps,
Luc

Hi,

Consider a node surrounded by 6 triangles. There are 6 segments which are DIRECTLY connected to the node. The rest of the 6 segments form a HEXAGONAL structure. So in total, how many segments should i consider?


Thanks
sathya

With your example of a node surrounded by 6 triangles, only the six segments are included in the sum of lengths.

Luc

Hello,

This is for the Finite Volume options. On the Finite Element side, the local mesh size is considered to be the square root of twice the triangle area. This is true only if the mesh is not stretched. Distributive advection schemes (4,5,13,14) have their own formula that stems from their stability criterion.

With best regards,

Jean-Michel Hervouet