(rpsetvar 'les-2d? #t)Voila!
This will enable LES in 2D models. Note that turbulence is inherently a 3D phenomenon and using LES for two dimensional flows is not recommended. However, in certain cases such as code benchmarks or debugging, it is useful to run LES in 2D. I would also speculate that LES is a valid model in axisymmetric conditions.