Hi Jain,
     
"If I have a discontinuous(across element interface) distribution of var, then what has been done during the above procedure?"
- You have projected your variable/field on CG Field. i.e. introduced C0 continuity across boundaries of the element.
- You projected your field on a field which has C0 continuity at element boundaries.

Example:
-Let us assume your var is a piece-wise p1(eg:3) degree polynomial. Exactly dis-continuous at element boundaries. 
    - Let us assume you are projecting your var on a field of p1.
    - if you would have used MultiRegions::DisContField2D. The two operations would not have affected your variable. .i.e. var = var_smooth, var_smooth is C^{-1}(dis-cont) at element boundaries and p1 polynomial inside each element.
    - Since you have used MultiRegions::ContField2D, Your var_Smooth has C0 continuity and you have p1 polynomial inside each element, but var != var_smooth. (Since you have reduced the degree of freedom).

The best section to read in the book would be section 2.2 from page 21.



Ashok. 



On Sun, Mar 26, 2017 at 2:02 PM, Jian Yu <yuj@buaa.edu.cn> wrote:
 Dear everyone,

 I am trying to figure out the specific formulation when performing C0Projection, i.e.
 If I define  m_c0ProjectExp as following
 
 m_c0ProjectExp = MemoryManager<MultiRegions::ContField2D>::  AllocateSharedPtr(m_session,m_graph,"DefaultVar");

Then what is the specific algorithm when perform the following command(all relative options are default)?
 m_c0ProjectExp->FwdTrans(var,var_Coeffs);
 m_c0ProjectExp->BwdTrans(var_Coeffs,var_smooth);

If I have a discontinuous(across element interface) distribution of var, then what has been done during the above procedure?

Could anyone please recommend me some materials on this?  If possible, where can I find this topic on the book "Spectral/hp Element Methods for Computational Fluid Dynamics"

Thank you in advance!

Best wishes,

Jian Yu

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