Dear Kamil, I had not realised they were not defined. Essentially we have 1) MODIFIED - a hierarchical/modified expansion basis where the quadrature order is exact for linear operations in a regular shaped element 2) GLL_LAGRANGE - a nodal expansion basis where the quadrature order is exact for linear operations in a regular shaped element 3) GLL_LAGRANGE_SEM - a nodal expansion basis where the quadrature order is not quite exact for linear operations in a regular shaped element but gives a diagonal mass matrix in quadrilateral or hexahedral elements. (2) and (3) are mainly set up for Quadrilateral or Hexahedral expansions where as (1) is suitable for hybrid meshes using different shaped elements. It is not so easy to define which is best for pipe flow etc since typically Quadrilateral/Hexahedral elements are more efficient but you have to be able to make a suitable mesh. You then get geometric flexibility using triangular/tetrahedral elements which tends to make us use a MODIFIED expansion. Hope this helps. Spencer. On 26 Sep 2014, at 08:50, Kamil Ozden <kamil.ozden.me@gmail.com> wrote:

Dear All,

I searched the web site of Nektar++ but I couldn't find any detailed information about the EXPANSION types (MODIFIED, GLL_LAGRANGE & GLL_LAGRANGE_SEM) used when using IncNavierStokesSolver. What are the differences between these Expansion types? Which one of these expansion types is the most suitable for problems like pipe flow or blood flow in vessels etc. ?

Regards, Kamil

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Spencer Sherwin McLaren Racing/Royal Academy of Engineering Research Chair, Professor of Computational Fluid Mechanics, Department of Aeronautics, Imperial College London South Kensington Campus London SW7 2AZ s.sherwin@imperial.ac.uk +44 (0) 20 759 45052