Hi Spencer,

 

Thank you very much for your last advice. But I have an additional problem for 3DHomogeneous1D case. My problem is how to get correct data-offset after operation  m_fields[0]->HomogeneousBwdTrans(). As I know, the HomogeneousBwdTrans() operation includes TransposeYZtoX()，which means it is SEM ordering, so I think I should define the data-offset as follow,

for(int i=0; i<num_exp; ++i)

  for(int j=0; j<num_planes; ++j)

    for(int q=0; q<nq;++q)

       offset = i*num_planes*nq+j*nq+q;

 

However, when I use above procedure to get values in physical space, it gives me wrong answer. Could you please give me some advice on this problem ?

 

 

zhicheng 


On Sun, Jun 14, 2015 at 7:10 PM Sherwin, Spencer J <s.sherwin@imperial.ac.uk> wrote:
Dear Zhicheng,

After a look over your suggestion I think your approach is generally correct. However I am not sure  you should be using the “MultiRegions::eGlobal” argument in IProductWRTbase. This option is stating that it will place the global coefficients into a storage format where every global degree of freedom is only stored one (hence the eGlobal). Normally we keep the coefficient space in local or elemental format. This seems to be how you are requesting the IProductWRTDerivBase to be stored.

Best regards,
Spencer.

On 11 Jun 2015, at 03:02, Zhicheng Wang <wangzhicheng09@gmail.com> wrote:

  

Hi All,

    I'd like to use explicit scheme to discretize the diffusion term in the case  of 3DHomogeneous1D in continuous Galerkin projection framework. For example, I have an array u, which stores the value of first component of velocity vector in Fourier spoace. and I want to calculate the inner product (grad w, grad u), where w is the base function, grad is gradient operator. Could following code get the correct result?

 

m_fields[0]->PhysDeriv(0,u ,u_derv[0]); // gradient in x direction

m_fields[0]->PhysDeriv(1,u, u_derv[1]); // gradient in y direction

 

for(unsigned int i=0; i<num_planes; ++i)

  {

double beta  = 2*M_PI*m_trans->GetK(i)/m_homoLen;

       beta *= beta;

m_fields[0]->GetPlane(i)->IProductWRTDerivBase(0, &u _derv[0]+i*np, &wkCoef1[0] +i*nc);    //

                                                m_fields[0]->GetPlane(i)->IProductWRTDerivBase(1, &u _derv[1]+i*np, &wkCoef1[0]+i*nc);

 

    m_fields[0]->GetPlane(i)->IProductWRTBase(tmp1 = &u[0]+i*np, &wkCoef2[0]+i*nc,MultiRegions::eGlobal);

    Vmath::Smul(nc, beta, &wkCoef2[0] + i*nc, 1, &wkCoef2[0]+ i*nc, 1);

 

   }

  Vmath::Vadd(NumTotCoeffs,wkCoef0,1,wkCoef1,1,diff,1);

  Vmath::Vadd(NumTotCoeffs,wkCoef0,1,wkCoef2,1,diff,1);  // array diff stores the final diffusion value

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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

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