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====== couette ======

''couette'' integrates plane Couette or channel flow from a given initial condition and save velocity fields to disk at a regular interval. (It should probably be called ''integrate''; I might change it to that in the next release.)

====== main options ======

<code>
  -T0       --T0                <real>      default == 0           start time
  -T1       --T1                <real>      default == 100         end time
  -dt       --dt                <real>      default == 0.03125     timestep
  -dT       --dT                <real>      default == 1           save interval
  -ts       --timestepping      <string>    default == sbdf3       timestepping algorithm
  -nl       --nonlinearity      <string>    default == rot         method of calculating nonlinearity,
  -o        --outdir            <string>    default == data/       output directory
  -R        --Reynolds          <real>      default == 400         Reynolds number
  -c        --channel                                              channelflow instead of plane Couette
  -b        --bulkvelocity                                         hold bulk velocity fixed, not pressure gradient
  -P        --dPdx              <real>      default == 0           value for fixed pressure gradient
  -U        --Ubulk             <real>      default == 0           value for fixed bulk velocity
  <flowfield>      (trailing arg 1)                                initial condition
</code>

[[docs:utils:couette:alloptions|Complete option list]]

==== time intervals ====

The integration starts at ''t=T0'' and saves data at times ''t = T0 + n dT'', exactly. The ''dt'' 
value is //approximate//. Channelflow actually rounds ''dt'' to the closest integral divisor of ''dT''
so that the save interval is exactly what you asked for. Data is saved to disk in files named ''u0.ff, u1.ff, u2.ff, ...'' if ''t'' takes on integer values or filenames with four-digit precision if ''t'' otherwise, e.g. ''u0.000.ff, u0.125.ff, u0.250.ff, ...''. The integration stops when ''t = T0 + n dT > T1.''

==== timestepping ====

The ''-ts'' or ''--timestepping'' sets the finite-difference time stepping algorithm. It takes the following 
values

^value^  %%O(dt^n)%%  ^algorithm^
|''cnfe1''|  1  |Crank-Nicolson Forward Euler|
|''cnab2''|  2  |Crank-Nicolson Adams-Bashforth|
|''smrk2''|  2  |Spalart-Moser Runge-Kutta|
|''sbdf1''|  1  |Semi-implict Backwards Differentiation|
|''sbdf2''|  2  |Semi-implict Backwards Differentiation|
|''sbdf3''|  3  |Semi-implict Backwards Differentiation|
|''sbdf4''|  4  | Semi-implict Backwards Differentiation|

==== nonlinearity ====

====== Usage examples ======


Integrate
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