====== continuefields ======
Quadratic extrapolation of FlowField u(mu) as function of parameter mu, where mu is one of Reynolds number, //dP/dx, Lx, Lz, Lx/Lz, sqrt(Lx^2 + Lz^2),// or the length between the starting //(Lx,Lz)// and a target value of //(Lx,Lz)//.
====== options ======
continuesoln :
(ALPHA VERSION!) continue invariant solution of plane Couette flow in Reynolds number
options :
-r --restart start from three previously computed solutions
-eqb --equilibrium search for equilibrium or relative equilibrium (trav wave)
-orb --periodicorbit search for periodic orbit or relative periodic orbit
-poinc --poincare (relative) periodic orbit search constrained to I-D=0 Poincare section
-xrel --xrelative search over x phase shift for relative orbit or eqb
-zrel --zrelative search over z phase shift for relative orbit or eqb
-contRe --continueRe continue solution in Reynolds number
-contdPdx --continuedPdx continue solution in imposed pressure gradient
-contLx --continueLx continue solution in streamwise width Lx
-contLz --continueLz continue solution in spanwise width Lz
-contAsp --continueAspect continue solution in aspect ratio Lx/Lz
-contDiag --continueDiagonal continue solution along diagonal with const aspect ratio Lx/Lz
-contLtarg --continueLtarget continue solution towards a target Lx,Lz
-up --upwards for non-restart searches, search in dir of increasing free parameter
-Lxtarg --LxTarget default == 6.28319 aim for this value of Lx
-Lztarg --LzTarget default == 3.14159 aim for this value of Lz
-T --maptime default == 20 initial guess for orbit period or time of eqb/reqb map f^T(u)
-R --Reynolds default == 400 Reynolds number
-dPdx --dPdx default == 0 imposed mean pressure gradient
-s0 --s0 default == 0 start value for arclength (arbitrary)
-ds --ds default == 0.0001 initial arclength increment for quadratic extrapolation
-adt --adjustDt adjust dt between continuation steps to keep CFL in bounds
-dsmin --dsmin default == 1e-08 minimum arclength increment (in normalized D,Re space)
-dsmax --dsmax default == 0.05 maximum arclength increment (in normalized D,Re space)
-errmin --errmin default == 1e-05 minimum error for extrapolated guesses
-errmax --errmax default == 0.0001 maximum error for extrapolated guesses
-sigma --sigma file containing sigma of sigma f^T(u) - u = 0 (default == identity)
-symms --symmetries file containing generators of isotropy group for symmetry-constrained search
...
-o --outdir default == ./ output directory
-log --logfile default == findsoln.logoutput log (filename or "stdout")
-dg --digits default == 8 number of digits for ReD.asc
(trailing arg 1) initial guess for Newton search
====== Usage ======
===== start-up mode =====
There are two basic modes for starting a continuation: from scratch (a single previous solution), or from a previous continuation (using three successive steps). Starting from scratch looks like this
continuesoln -eqb -contRe -R 350 uRe350.h5
The trailing argument here is a FlowField which is assumed to be a solution of the specified type at the specified parameters (or a good guess for a solution). The continuation will begin by making very small +/- perturbations in the continuation parameter (here Reynolds number) and finding new solutions at that value using the input field as an initial guess. By default the continuation goes down in the parameter. If you want to go up, use the ''-up'' option.
Starting from a previous continuation looks like this
continuesoln -eqb -contRe --restart ../contRe0/search-14 ../contRe0/search-15 ../contRe0/search-16
The trailing three arguments are directories containing results from a previous run of ''continuesoln''. The direction of continuation is determined by the order of the three previous solutions.
===== continuation parameter =====
''continuesoln'' will continue solutions in one of seven parameters:
-contRe --continueRe continue solution in Reynolds number
-contdPdx --continuedPdx continue solution in imposed pressure gradient
-contLx --continueLx continue solution in streamwise width Lx
-contLz --continueLz continue solution in spanwise width Lz
-contAsp --continueAspect continue solution in aspect ratio Lx/Lz
-contDiag --continueDiagonal continue solution along diagonal in Lx,Lz with const aspect ratio Lx/Lz
-contLtarg --continueLtarget continue solution towards a specified Lx,Lz pair
The target //Lx,Lz// for ''-contLtarg'' is specified by these options
-Lxtarg --LxTarget default == 6.28319 aim for this value of Lx
-Lztarg --LzTarget default == 3.14159 aim for this value of Lz
Two other options related to the continuation type are
-up --upwards continue upwards in parameter (default is downwards)
-adt --adjustDt adjust dt between continuation steps to keep CFL in bounds
The ''-up'' option is self-explanatory. The ''-adt'' option is most important when the continuation changes //Lx//, since this will change the //x// gridspacing and consequently the CFL number. It should be safe to use ''-adt'' in other cases, too.