Hello everyone, I am using the incompressible solver in Nektar++ for simulating vortex flows around bluff bodies or slender bodies. The results obtained look fine, and the velocity and pressure fields are smooth, but as I exported the results into post-process software, like Tecplot, for calculating vorticity, the vorticity obtained is not smooth. I looked into the reason and found that the vorticity inside each element was calculated separately, so the vorticty values at the boundary between elements are discontinuous. I guess that this should be a special issue existing in spectral element grids, and no this kind of problem exists in finite volume grids. This is also applicable to calculating other derivative quantities, like in Q or lambda2 methods for vortex identification. I'd like to know if there is some approaches to deal with this problem. Otherwise, it is difficult to visualize vortex structures. Many thanks. Baofeng Baofeng Ma, PH.D Associate Professor Institute of Fluid Mechanics School of Aeronautical Science and Engineering Beihang University Email: bf-ma@buaa.edu.cn Tel: 0086 (0)10 82338344