[Nek5000-users] How to obtain spectral coefficients and basis

[nek5000-users at lists.mcs.anl.gov]

Hello,

If I've understood you propely, you can see all the collocation points and
weights in the file coef.f (subroutine genwz).

Andrew

2015-12-07 4:23 GMT+01:00 <nek5000-users at lists.mcs.anl.gov>:

> Hello,
>
> I'm trying to represent the solution, either velocity or temperature, in
> terms of spectral basis, i.e.
>
> $u=\Sigma a_i \phi_i $ with $\phi_i$ as the basis and $a_i$ as the
> coefficients.
>
> I have two questions:
>
> 1) (a naive one!) Which basis is being used in Nek5000? I assume it is
> Chebyshev polynomials. Is that true? If not, what is the basis?
>
> 2) How can I retrieve the coefficients $a_i$? Also, is there a way to
> access such coefficients during the solution, say by writing them to a file?
>
> I really appreciate the responses. As a side note, I'd like to use DNS
> data for model reduction.
>
> Many thanks,
> Saleh
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