gtspring2009:howto:findsoln

For now this discussion is limited to finding equilibria. See also

We expect to find equilibria in symmetry groups that contain sign changes in both x and z. See our PCF equilibrium paper for details. Chose any symmetry group containing σxz, for example,

Generate an initial condition in this symmetry group. One way to get a decent initial condition is to randomly perturb a known solution and then project onto the right symmetry group. For example, download the Nagata upper branch and then

perturbfield --magnitude 0.01 eq2 eq2perturb symmetryop -sx -sy -sz -az 0.5 eq2perturb s3eq2pertub addfields 0.5 eq2perturb 0.5 s3eq2perturb eq2perturbsymm

This sequence of commands constructs

eq2perturb = eq2 + 0.01 (random perturbations) s3eq2perturb = s3(eq2perturb) eq2perturbsymm = 1/2 (eq2perturb + s3eq2perturbsymm)

The final field eq2perturbsymm will be eq2 plus some s3-symmetric perturbations.

Next generate a sequence of s3-symmetric data by integrating the initial condition

couette -symms sxz.asc -T0 0 -T1 1000 eq2perturbsymm

The `-symms sxz.asc`

option restricts the integration to a symmetric subspace specified by the file `sxyz.asc`

. Here there is just one generator and the file should be

% 1 1 -1 -1 -1 0 0

See the FieldSymmetry docs for more on the file formats.

Now search for a new solution using random samples of the turbulent simulation data

mkdir findorbit-u500 cd findorbit-u500 findorbit -eqb -symms sxz.asc ../data/u500

Keep an eye on the file convergence.asc. If the residual gets to 1e-08 or so you're on your way to a solution.

gtspring2009/howto/findsoln.txt · Last modified: 2010/02/02 07:55 (external edit)