LRR Rstm pipe flow takes too long to get fully developed
 

Dear foamers,

I'm setting up a pipe flow and comparing this to Eggels data for pipe flow at Re = 5500. k-omega-SST yields "almost" satisfying results, and now I'm trying with LRR Rstm turbulence model instead. So far the plots for 'k' seems ok, but a thing that worries me is that it takes so long for the flow to get fully developed.

I include here a screenshot with a number of different plots, showing how axial velocity varies along the entire pipe length, and far beyond the "5 X diameter" rule.

Also included is the residuals plot. I feel it's clearly something fishy going on here, as the pressure and U_y and U_z never drops below 0.001, even though they they are set in fvSolutions (both tolerance and relTol) to limits far below.

Suggestions on to how to improve this? :)