[Nek5000-users] mesh precision

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

Hi Frank,

For most engineering calculations, single precision is
sufficient and the code was written w/ this in mind.

That being said, for convergence studies and for stability
simulations like yours, it can be of use to have higher
precision.

In fact, I'm wondering if that's the source of difficulty
in your current high Reynolds number runs - but haven't
had time yet to test this hypothesis.   My std. approach
is to project the input coordinates, xc(), yc(), and zc(),
onto the cylinder in usrdat(), at which point they are
then used to generate the geometry arrays, xm1, ym1, zm1.

usrdat() was originally designed for precisely this type
of application.

hth,

Paul


On Thu, 29 Apr 2010, nek5000-users at lists.mcs.anl.gov wrote:

> Hello all,

>From the *.rea files I have seen (including in the examples), all
numbers describing the mesh are single precision.  I am wondering why
that is the case; would not double precision values be better?

Cheers,
Frank

-- 
Frank Herbert Muldoon, Ph.D. Mechanical Engineering
Technische Universität Wien (Technical University of Vienna)
Inst. f. Strömungsmechanik und Wärmeübertragung (Institute of Fluid
Mechanics and Heat Transfer)
Resselgasse 3
1040 Wien
Tel: +4315880132232
Fax: +4315880132299 
Cell:+436765203470
fmuldoo (skype)
http://tetra.fluid.tuwien.ac.at/fmuldoo/public_html/webpage/frank-muldoon.html

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