[Nek5000-users] Spectral method with Nek

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

This is absolutely true - one element corresponds to a spectral calculation.

You do need, however, enough points to resolve the scales of motion, as is always
the case, which means you need large values of N.   (The first spectral results were
32^3, and then the breakthrough 100^3 by Orszag in the early 70s - the famed centicubed
simulations.)

Paul

________________________________________
From: nek5000-users-bounces at lists.mcs.anl.gov [nek5000-users-bounces at lists.mcs.anl.gov] on behalf of nek5000-users at lists.mcs.anl.gov [nek5000-users at lists.mcs.anl.gov]
Sent: Tuesday, August 02, 2016 10:53 AM
To: nek5000-users at lists.mcs.anl.gov
Subject: [Nek5000-users] Spectral method with Nek

All,

I was wondering if the following statement is true or false:

"If a single element is used for the whole domain then one can claim the
Nek simulation is spectral instead of spectral element".

Based on this, I carried out DNS on cavity for relatively large Reynolds
numbers and I was not able to capture the instability mechanisms with
one element (even when I increased the power of polynomial to 12 or 18).
While I'm not surprised, I just wanted to see if anyone else has a
similar experience.

As a side question, why Nek utilizes Legendre polynomials instead of
Chebyshev for each element? Is this because we're also interested in
modeling non-uniformly spaced nodes?

Best,
Saleh
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