Erm, it's not turbulent, at least not in the engineering sense. Medics (and geologists) have a slightly different definition for turbulent flow. They assume (incorrectly) that eddies in the flow imply turbulence, rather than being laminar eddies. What you're seeing is (probably) eddy formation from part of the geometry, and you may want to read up on DVT and aneurysms for why that may be bad. Convergence may be a little poor as the flow may be inherently transient - please post a screen shot of the residuals.
If you really want turbulence you can use a UDF as that bypasses the checks: they were added in v6.0 because I tested it and didn't know you couldn't have turbulence & nonNewtonian flow at the same time, at least not reliably with the models we had. There is low Re option, under