Convergence of laminar flow model for high Re
 

Hi,

If I understand correctly, the laminar solution of Navier stokes equations is valid for all Re. Then why do commercial solvers like CFX are notable to converge above a certain Re (like 2300 for pipe flow) with laminar flow assumption. I understand the solution may not be entirely physical (as it takes special care to maintain laminar flow at high Re in experiments and normally flow becomes turbulent) but still it is a solution of the governing equations.
Please explain !
Thanks