programming:transform_spectral_coeff_to_physical_data_points
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programming:transform_spectral_coeff_to_physical_data_points [2010/08/28 10:47] 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 from an object Flowfield u, I have compared the results of the expansion with the value given by the method u.makephysical(). I do not obtain the same results. | + | I 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. | 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, | Regards, | ||
| Emmanuel | Emmanuel | ||
| Line 28: | Line 36: | ||
| //display gridpoint coordinates 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(); | ||
| Line 37: | Line 45: | ||
| 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; | ||
| Line 45: | Line 53: | ||
| - | Example of results displayed : | ||
| - | { | ||
| - | 0 -0.995185 0 // x,y,z | ||
| - | |||
| - | 0.00258953 // u computing Fourier series | ||
| - | |||
| - | 0.00604268 // return of u.makePhysical | ||
| - | } | ||
programming/transform_spectral_coeff_to_physical_data_points.1283017630.txt.gz · Last modified: 2010/08/28 10:47 by emmanuel
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