This program solves the N-S equations in 2D using pseudo spectral algorithm
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COMPILING INSTRUCTIONS
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To compile, run 'make ns2d' in current directory
'make clean' removes .o files
'make clean_data' removes all data files
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RUNNING INSTRUCTIONS
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ns2d takes four input files
ns2d input1 input2 input3 input4
input1 should contain variables in the format
 'resolution' 'no_of_Iterations' 'delta_t' 'viscosity' 'force_amplitude' 
 'coeficient of friction' 'kf' 'nthreads' 'nthr_omp' 'flag' 'pflag' 's_flag'
 to store the velocity field data, set pflag = 0 and flag sets the resolution of stored data
input2 initializes vorticity in fourier space and should contain data
 in row major format (both real and imaginary part together)
If input2 is '0', program assumes a default vorticity profile
input3 should contain data on particles in format 'no of particles' 'tau'
input4 initializes particle positions and velocities
If input4 is '0', program assumes random positions and zero velocity for particles
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The output data is stored after every 1/s_flag th of total iterations
output data files stored are
 total energy vs time in 'spectra/energy.dat'
 energy vs k in 'spectra/eSpectra(n).dat'
 velocity and vorticity profile in 'field/velProfile(n).dat'
 particle position in 'particle/particle(n).dat'
The output vorticity in fourier space is stored in 'init_flow.dat' and
 particle positions in 'init_part.dat'
memory required : approx 50 MB for systemSize 1024 (varies as square of systemSize, without particles)
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fourier transforms are evaluated using fftw2.1.5 routines
fftw2.1.5 documentation available at http://www.fftw.org/fftw2_doc/
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author : Martin James
martin.nilambur@gmail.com
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