[Nek5000-users] Built in FFT?

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

Hi Michael,

Since you want only a few modes, one option would be to 
simply integrate against the desired Fourier modes,
cos (k pi x)*cos (l pi y), etc.

Paul




On Tue, 27 Jul 2010, nek5000-users at lists.mcs.anl.gov wrote:

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> Hi Paul,
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> This questions involves generating turbulent inflow conditions.  At the moment, I am initializing a flow using the Walsh solution and recycling it which is working well, but we would like to have more control over the conditions such as  maintaining a desired intensity. At the moment, I am using a double periodic box for the recycling portion, however the flow structure is dampened out as it is recycled.  
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> So, Similar to how the velocity is scaled at the recycling plane to maintain a constant flow rate, we wish to also impose predescribed statistical properties by looking at the energy spectrum, and scale the the first few large scale modes to a desired/predetermined spectrum before scaling the velocity and copying it to the inflow plane. 
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> To do this, we would take a spatial FFT of either the recycling plane, or the recycling box as a whole. So I was curious to see if there was anything built in to work with before looking around.
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> - Michael
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> ----- Original Message -----
> From: nek5000-users at lists.mcs.anl.gov
> To: "Nekton User List" <nek5000-users at lists.mcs.anl.gov>
> Sent: Tuesday, July 27, 2010 4:39:46 PM GMT -06:00 US/Canada Central
> Subject: Re: [Nek5000-users] Built in FFT?
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> Hi Michael, What is it that you're trying to do ? Paul
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> On Tue, 27 Jul 2010, nek5000-users at lists.mcs.anl.gov wrote:
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>>>> Hello, > > > > I am wondering if Nek has a built in subroutine for doing an FFT?   I haven't seen anything so far but thought I would inquire about it.
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> Â > > > > Thanks, > > Michael >
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