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).
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 <real> default == 6.28319 aim for this value of Lx
-Lztarg --LzTarget <real> default == 3.14159 aim for this value of Lz
-T --maptime <real> default == 20 initial guess for orbit period or time of eqb/reqb map f^T(u)
-R --Reynolds <real> default == 400 Reynolds number
-dPdx --dPdx <real> default == 0 imposed mean pressure gradient
-s0 --s0 <real> default == 0 start value for arclength (arbitrary)
-ds --ds <real> default == 0.0001 initial arclength increment for quadratic extrapolation
-adt --adjustDt adjust dt between continuation steps to keep CFL in bounds
-dsmin --dsmin <real> default == 1e-08 minimum arclength increment (in normalized D,Re space)
-dsmax --dsmax <real> default == 0.05 maximum arclength increment (in normalized D,Re space)
-errmin --errmin <real> default == 1e-05 minimum error for extrapolated guesses
-errmax --errmax <real> default == 0.0001 maximum error for extrapolated guesses
-sigma --sigma <string> file containing sigma of sigma f^T(u) - u = 0 (default == identity)
-symms --symmetries <string> file containing generators of isotropy group for symmetry-constrained search
...
-o --outdir <string> default == ./ output directory
-log --logfile <string> default == findsoln.logoutput log (filename or "stdout")
-dg --digits <int> default == 8 number of digits for ReD.asc
<flowfield> (trailing arg 1) initial guess for Newton search
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.
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
Two other options related to the continuation type are
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.