# esys.modellib.flow Package

## Classes

- `SteadyIncompressibleFlow`

class `esys.modellib.flow.``SteadyIncompressibleFlow`(**kwargs)

  Bases: `esys.escriptcore.modelframe.Model`

  > *-left(etaleft(v_{i,j}+v_{j,i}

  ight) ight)_{,j}+p_{,i}=F_i*

  > sigma_{ij}=2eta D_{ij}-p,delta_{ij}

  > *D_{ij}=

  rac{1}{2}left( v_{j,i} + v_{i,j } ight)*

  > v_{k,k} = 0

  `__init__`(**kwargs)

    set up model

  `UNDEF_DT` = 1e+300
  `checkLinkTargets`(models, hash)

    Returns a set of tuples (“<self>(<name>)”, <target model>) if the parameter <name> is linked to model <target model> but <target model> is not in the list of models. If a parameter is linked to another parameter set which is not in the hash list the parameter set is checked for its models. hash gives the call history.

  `declareParameter`(**parameters)

    Declares one or more new parameters and their initial value.

  `declareParameters`(parameters)

    Declares a set of parameters. parameters can be a list, a dictionary or a ParameterSet.

  `doFinalization`()

    Finalizes the time stepping.

    This function may be overwritten.

  `doInitialPostprocessing`()

    Finalises the initialization iteration process. This method is not called in case of a restart.

    This function may be overwritten.

  `doInitialStep`()

    Performs an iteration step in the initialization phase. This method is not called in case of a restart.

    This function may be overwritten.

  `doInitialization`()

    initialize model

  `doStep`(dt)

    performs an iteration step of the penalty method. IterationDivergenceError is raised if pressure error cannot be reduced or max_iter is reached.

  `doStepPostprocessing`(dt)

    Finalises the time step.

    dt is the currently used time step size.

    This function may be overwritten.

  `doStepPreprocessing`(dt)

    step up pressure iteration

    if run within a time dependend problem extrapolation of pressure from previous time steps is used to get an initial guess (that needs some work!!!!!!!)

  `finalize`()

    Returns False if the time stepping is finalized.

    This function may be overwritten.

  classmethod `fromDom`(esysxml, node)
  `getAttributeObject`(name)

    Returns the object stored for attribute `name`.

  `getSafeTimeStepSize`(dt)

    Returns a time step size which can be safely used.

    `dt` gives the previously used step size.

    This function may be overwritten.

  `hasAttribute`(name)

    Returns True if self has attribute `name`.

  `releaseParameters`(name)

    Removes parameter name from the parameters.

  `setUp`()

    Sets up the model.

    This function may be overwritten.

  `showParameters`()

    Returns a description of the parameters.

  `stress`()

    returns current stress

  `stretching`()

    returns stertching tensor

  `terminateInitialIteration`()

    Returns True if iteration at the inital phase is terminated.

  `terminateIteration`()

    iteration is terminateIterationd if relative pressure change is less than rel_tol

  `toDom`(esysxml, node)

    `toDom` method of Model class.

  `trace`(msg)

    If debugging is on, prints the message, otherwise does nothing.

  `writeXML`(ostream=<_io.TextIOWrapper name='<stdout>' mode='w' encoding='utf-8'>)

    Writes the object as an XML object into an output stream.

## Functions

## Others

## Packages