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programming:transform_spectral_coeff_to_physical_data_points [2010/08/28 10:35]
emmanuel
programming:transform_spectral_coeff_to_physical_data_points [2010/08/28 16:08] (current)
emmanuel
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 Dear Prof. Gibson, Dear Prof. Gibson,
  
-I would like to transform ​the spectral coefficients in physical values by evaluating the expansion sum (eqn 20 in the user's manual.) +We can determine ​the physical values ​from the spectral coefficients ​by evaluating the expansion sum (eqn 20 in the user's manual.)  
-Starting form an object Flowfield u, have compared the results of the expansion ​with the value given by the method makephysical(). I do not obtain ​the same results. ​+wanted to compared the physical values computed by this sum with the values returned ​by the method ​u.makephysical(). ​This method use the FFTW algorithm and  
 +I was expecting no difference. The fact is that, I do not obtained ​the same results. 
 + 
 I have attached part of the code I am using. Do you think that something is incorrect ? I have attached part of the code I am using. Do you think that something is incorrect ?
 +
 +As the width of the channel is [a,b] = [-1.0,1.0], I haven'​t normalized the Chebyshev polynomials.
 +
 +Example of results displayed :
 +  0.00258953 ​     // u from expansion sum
 +  0.00604268 ​     // return of u.makePhysical (FFTW)
 +
 +
 +Regards,
 +Emmanuel
  
   {   {
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    ny = 5;     ny = 5; 
    nz = 5;       nz = 5;   
-  //display gridpoint ​coordiantes ​x,y,z+  //display gridpoint ​coordinates ​x,y,z
   std::cout << u.x(nx) << ' ' << u.y(ny) << ' ' << u.z(nz) << endl ;   std::cout << u.x(nx) << ' ' << u.y(ny) << ' ' << u.z(nz) << endl ;
 +  ​
   //compute physical value using expansion sum and display   //compute physical value using expansion sum and display
    ​u.makeSpectral();​    ​u.makeSpectral();​
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           std::cout << 2.0 * sum_u.real()<<​ endl ;           std::cout << 2.0 * sum_u.real()<<​ endl ;
        
-   //display physical value  from makePhysical() ​  +    ​//display physical value  from makePhysical() ​  
     u.makePhysical();​     u.makePhysical();​
-    std::cout << u(nx,​ny,​nz,​0) ​    ​<< ​ endl ;+    std::cout << u(nx,​ny,​nz,​0) ​ << ​ endl ;
   ​   ​
     std::cin >> pause;      std::cin >> pause;
     }     }
-   ​Regards,​ + 
-   Emmanuel+ 
programming/transform_spectral_coeff_to_physical_data_points.1283016934.txt.gz · Last modified: 2010/08/28 10:35 by emmanuel