wiggle for wall shear stress
 

I simulated the convection-diffusion equations coupled with the navier-stokes equation in the 3-dimensional curved circular vessel implanted the drug-eluting stent. When I plot the wall shear stresses along the wall, I found the wiggle downstream of the stent. I created the tetrahedral volume mesh in gambit and had approximately 1 million cells. I think it is the mesh problem, so I tried to remove the wiggle to rearrange the mesh, but it did not disappear. Could anybody tell me the other possible things to do? Thank you in advance.