Diagnostic fields¶
Some stand-alone functions are available in the diagnostics.py file
for computing flow diagnostics.
Courant number¶
The Courant number diagnostic computes the field defined by
\[\frac{||\mathbf{u}||\Delta t}{\Delta x},\]
where \(\Delta t\) is the time-step size and \(\Delta x\) is the element size (more specifically, it is twice the element’s circumradius).
Grid Reynolds number¶
The Reynolds number (whose length scale is relative to the element size \(\Delta x\)) is defined by
\[\mathrm{Re} = \frac{\rho||\mathbf{u}||\Delta x}{\mu},\]
where \(\rho\) is the fluid density, \(\mu\) is the dynamic viscosity, and \(||\mathbf{u}||\) is the magnitude to the velocity field. Alternatively,
\[\mathrm{Re} = \frac{||\mathbf{u}||\Delta x}{\nu},\]
where \(\nu\) is the kinematic viscosity.
Divergence¶
This diagnostic field computes the divergence
\[\nabla\cdot\mathbf{u},\]
of a vector field \(\mathbf{u}\).