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</o:shapelayout></xml><![endif]--></head><body lang=EN-MY link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span lang=EN-US>Dear Neks<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>I have my turbulent flow in a 3D box for which I would like to perform a Fourier analysis in one direction (y) at several selected time steps in order to find the discretized spectral representation (up to resolution of say N=128 wave numbers) of streamwise vorticity (w_x). I have been trying to find the best way to approach this in nek by reading the user mailing list but am troubled to decide and would appreciate it if the experienced users could guide me:<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l1 level1 lfo1'><![if !supportLists]><span style='mso-list:Ignore'>1)<span style='font:7.0pt "Times New Roman"'> </span></span><![endif]><span dir=LTR></span><span lang=EN-US>Using int_tp tool (in repo, trunk/tool/) one can interpolate the nek SEM output results to uniform, SEM and non-uniform (selected points) but I guess this only works for small grids? At least I got seg fault for my larger grids. Alternatively, we can use “</span>ifreguo = .true.” in userchk via post-processing the data in parallel. And then use a separate fft library (eg. MATLAB) to read in the uniform grid and do fft. But there will be memory issues for larger datasets. How can I resolve this?<o:p></o:p></p><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l1 level1 lfo1'><![if !supportLists]><span lang=EN-US><span style='mso-list:Ignore'>2)<span style='font:7.0pt "Times New Roman"'> </span></span></span><![endif]><span dir=LTR></span><span lang=EN-US>I noticed that Visit has an FFT operator (at least in my v 2.6.3) for which I could not find any documentation. Does anyone have any knowledge of how it works?<o:p></o:p></span></p><p class=MsoListParagraph style='text-indent:-.25in;mso-list:l1 level1 lfo1'><![if !supportLists]><span lang=EN-US><span style='mso-list:Ignore'>3)<span style='font:7.0pt "Times New Roman"'> </span></span></span><![endif]><span dir=LTR></span><span lang=EN-US>One could also do the fft by adding proper subroutines in .usr file and calling them in userchk. Does anyone here have the right set of subroutines for this purpose?<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>Thank you,<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>Hesam<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p></div></body></html>