## ENH: SpalartAllmaras: add estimation functions for k, epsilon and omega

### Summary

- Adds estimation functions for
`k`

,`epsilon`

,`omega`

fields into the`SpalartAllmaras`

turbulence closure model, so that various utilities can be enabled with this model if necessary, e.g.`turbulenceFields`

function object. - Reduces peak-memory usage in the
`SpalartAllmaras`

model.

### Resolved bugs

N/A

### Details of new models

- The first test case was based on a direct-numerical simulation
by (Moser et al., 1999). The test case is a smooth-wall turbulent
plane channel flow wherein an internal flow statistically develops downstream
(until is fully developed) through parallel smooth walls that are two
characteristic-length apart. The friction Reynolds number of the flow is
`\mathrm{Re}_\tau = 180`

.

##### Turbulent kinetic energy

##### Turbulent kinetic energy dissipation rate

##### Turbulent kinetic energy production rate

##### Streamwise flow speed

##### Reynolds stress tensor components

### Risks

No known risks or user-input changes.

PS: Hi @vaggelisp, might affect or be relevant? just for your info in any case.