isoave.doc

Instructions on running the DNS code's multiple angle structure
function analsys package


Step 1. prepair the data

For data that was not produced by the dns code, we need to extract
each velocity component for each snapshot.  The DNS code also needs
the filenames to be in the form:   nameXXXX.XXXX.[uvw], where
the components are .u, ,v and .w, and the time is given by XXXX.XXXX.

Example used here from Mark Peterson:

64^3 data with 216 byte header, followed by density, velocity and other
fields:
  rstrt.0030.bin

# remove header and density:  (64^3 = 2097152 bytes)
tail -c +217 rstrt.0030.bin  > temp.bin
tail -c +2097153 temp.bin > temp2.bin           

# extract u
head -c 2097152 temp2.bin > rstrt0030.0000.u

# remove u, extract v
tail -c +2097153 temp2.bin > temp3.bin
head -c 2097152 temp3.bin > rstrt0030.0000.v

# remove v, extract w
tail -c +2097153 temp3.bin > temp4.bin
head -c 2097152 temp4.bin > rstrt0030.0000.w


Step 1.  Build the code

edit dns/src/analysis_isoave.F90
Near the top of the file, make sure: 
    header_type=2
    compute_uvw = .true.  
    tstart = 30
    tstop = 30


% cd dns/src
% ./gridsetup.py 1 1 2 64 64 64 2 2 0
% make analysis_isoave


Step 3.  Run the code:

mpirun -np 2 ./analysis_isaove -d /tmp -i  forcing12.inp  rstrt

the "-d /tmp" option specifies the directory where to read and write 
the data files.  If ommitted, it will use the  current working directory.  

"-i forcing12.inp" specifies the input file.  For data produced by
the dns code, you should use the input file used to produce the data.
In this example, we just use one of the included dns input files, 
forcing12.inp

"rstrt" is the name of the run.  
The code will read in /tmp/rstrt0030.0000.[uvw] and output
/tmp/rstrt0030.0000.new.isostr


Note: the output file contains epsilon, nu and KE.  These will
be computed from the value of "nu" in the forcing12.inp file.
They are used to scale the various structure functions.  
If you need the precise scaling correct, you need to put the correct
value of "nu" in forcing12.inp.  Also note that the DNS code is
assumes a box of length 1 ( other codes often assume 2pi), and
thus nu must be scaled accordingly.  

Step 4. Plot the structure functions

% cd dns/matlab
edit "isoave.m" and edit the line of code that specifies the
filename to look lilke this:

name='/tmp/rstrt0030.0000.new'
nx=64; delx_over_eta=2.95; epsilon=3.57; teddy=1.05; 
(the numbers mostly ignored so you can use any value)


figure 1:   4/5'ths law showing all 73 directions and the angle average.
figure 2:   4/15'th law
figure 3    4/3 law
figure 12, 13    even more esoteric structure functions

Note, since epsilon is incorrect in the output, the plots do not
fix within the axis.   You can either rerun analysis_isoave
with the correct viscosity in the input file, or just edit
compisoave.m and comment on the axis setting calls.