COMSOL 6.2 - Variables

Variables

Handle initial data and scaling for variables solved, as well as how variables not solved for are computed. The methods are applied for the dependent variables present as Field or State subattributes. These attributes are automatically created and updated by this feature. So, if the Analysis (for the solver sequence) is altered or if a different Analysis is used in the sequence, then the Field attributes are changed accordingly.

Syntax

model.sol(sname).create(fname,'Variables')

model.sol(sname).feature(fname).set(pname,pval)

model.sol(sname).feature(fname).feature(varname).set(pname,pval)

model.sol(sname).feature(fname).updateVariables()

Description

Operation feature. Computes the initial values for the variables that are solved for and how the variables not solved for are computed. The variables handled are the ones present as Field or State attributes. The feature also handles scaling and which variables to store in output.

Use the updateVariables method if needed to perform a manual update of the variables after some change that affects them.

Table 6-77: Valid Variables Properties.
Property	Values	Default	Description
clist	String array		Provide values for constants as input parameters using a string array; for the corresponding constant names, use cname. See The clist and cname Properties.
cname	String array		Provide names of constants as input parameters using a string array; for the corresponding constant values, use clist. See The clist and cname Properties.
control	String	user	Name of the controlling study step or user if the feature is controlled manually.
initmethod	init \| sol	init	Method used for initial value computation.
initsol	zero \| solution object	zero	Initial value solution object.
initsoluse	current \| manual \| solution store	current	Use current or stored values from the initial value solution object, or use manual to provide a solution index in the initsolusesolnum property.
initsolusesolnum	integer or parameter name		An outer solution index for a parametric sweep, such as a global parameter, when initsoluse is set to manual.
manualsolnum	positive integer		Identifies the solution used when solnum = manual.
notlistsolnum	vector of positive integers		List that identifies the solutions used when notsolnum = from_list.
notmanualsolnum	vector of positive integers		Identifies the solutions used when notsolnum = manual.
notsol	zero \| solution object	zero	Solution object for variables not solved for.
notsolmethod	init \| sol	init	Method used for variables not solved for.
notsolnum	auto \| all \| first \| last \| from_list \| interp \| manual \| positive integer	auto	Which solnums from other solution to use for variables not solved for.
notsoluse	current \| solution store	current	Use current or stored values from the solution object for variables not solved for.
nott	double		The interpolation value used for values of variables not solved for when notsolnum = interp.
resscalemethod	auto \| manual	auto	Method used for scaling of residual.
resscaleval	scalar	1	Residual scaling value, if resscalemethod is manual.
scalemethod	auto \| init \| none \| manual	auto	Method used for scaling of variables.
scaleval	scalar	1	Global scaling value, if scalemethod is manual.
solnum	auto \| all \| first \| last \| interp \| manual \| positive integer	auto	The solnum from other solution to use for initial values of variables solved for.
t	double		The interpolation value used for initial values of variables solved for when solnum = interp.
useinitsol	on \| off	off	Use user-controlled initial values of variables solved for.
usesol	on \| off	off	Use user-controlled values of variables not solved for.

Table 6-78: Valid Variable Subattribute Field/State Properties.
Property	Values	Default	Description
comp	vector of strings		Field/State components
out	on \| off	on	Store Field/State in output
reconstruct	String	none	Tag of a compatible reduced model to use for reconstruction when solvefor is off.
scalemethod	auto \| init \| none \| manual \| parent	parent	Method used for scaling of variables
scaleval	scalar	1	Scaling value
solvefor	on \| off	on	Solve for this Field/State
storesel	Array of selection strings		Selections defining which field data to store.
usestoresel	all \| selection	all	Store all field data or field data defined in selections in storesel.

The properties initmethod, initsol, and initsoluse determine the initial value for the solution components you solve for when useinitsol is set to on.

The properties notsolmethod, notsol, notsoluse, and notsolnum determine the value of solution components you do not solve when usesol is set to on.

Which variables to solve for, and which variables to store in the solution is controlled by the properties solvefor and out in the Field or State attributes.

The reconstruct property is only available when using model reduction and then to configure reconstruction for dependent variables not solved for.

The properties scalemethod and scaleval determine a scaling of the degrees of freedom that is applied in order to get a more well-conditioned system. The possible values of scalemethod are:

Table 6-79: Values for the Property scalemethod.
Value	Meaning
auto	The scaling is automatically determined.
init	The scaling is determined from the initial value. Use this if the sizes of the components of the initial value give a good estimate of the order of magnitude of the solution.
none	No scaling is applied.
manual	The scaling is user controlled by setting the property scaleval.
parent	Scaling method is inherited from the parent Variables feature (only for subattributes).