Non reproducible results with TVD scheme for advection of turbulence

When TVD scheme is selected for advection of turbulence (iopt_adv_turb = 3), results are not reproducible. That is, the exact same setup (Usrdef and input files) run two times leads to (slightly) different results.

This is an undesired behavior, but it is not observed with other schemes for advection of turbulence (iopt_adv_turb = 0, 1, 2).

This behavior was first reported by @pdenis for a project application with offshore structures.

All tests leading to this report were done by @hromanelli on NoS.

@pdenis will now test again her application with all possible values of iopt_adv_turb = 0, 1, 2, 3. We expect that that results will be reproducible with iopt_adv_turb = 0, 1, 2, but not with iopt_adv_turb = 3. She will also analyze TKE results with iopt_adv_turb = 0, 1, 2 and determine if using one of those options is acceptable for her project. If yes, we will keep this issue as is. If not, we will try to solve it.

As a remark, in the documentation, @pluyten writes: "Advection of turbulence is considered of less importance than the production and dissipation terms in the k, k-ε and k-l transport equations. It is recommended not to change the zero default value of iopt_adv_turb."

At this stage, there is too little knowledge of turbulence processes within the COHERENS teams and someone should invest time to improve on that. @ogourgue and @hromanelli will try to do that.