# SinDirichletBC

Imposes a time-varying essential boundary condition , where varies from an given initial value at time to a given final value over a specified duration.

## Description

SinDirichletBC is a NodalBC which imposes a time-varying boundary value of the form (1) where and are the initial and final values of , respectively, and is the final time. These values are controlled by the initial, final, and duration parameters, respectively. The value is applied on one or more sidesets specified by the boundary parameter and does not vary in space. This type of boundary condition is applicable to time-varying PDEs, for example: \begin{aligned} \frac{\partial u}{\partial t} -\nabla^2 u &= f && \quad \in \Omega \\ u &= g(t) && \quad \in \partial \Omega \end{aligned} and is frequently used to "ramp" a difficult boundary condition to its final value over a short time interval, rather than imposing it instantaneously at time . This approach can make nonlinear solvers more robust by improving the initial guess used by the Newton iterations, as well as preventing the solver from converging to non-physical solutions in nonlinear PDEs.

## Example Input Syntax


[BCs]
active = 'left right'

[./left]
type = SinDirichletBC
variable = u
boundary = 3
initial = 0.0
final = 1.0
duration = 10.0
[../]

[./right]
type = SinDirichletBC
variable = u
boundary = 1
initial = 1.0
final = 0.0
duration = 10.0
[../]
[]
(moose/test/tests/bcs/sin_bc/sin_dirichlet_test.i)

## Input Parameters

• variableThe name of the variable that this boundary condition applies to

C++ Type:NonlinearVariableName

Description:The name of the variable that this boundary condition applies to

• boundaryThe list of boundary IDs from the mesh where this boundary condition applies

C++ Type:std::vector

Description:The list of boundary IDs from the mesh where this boundary condition applies

### Required Parameters

• duration0

Default:0

C++ Type:double

• initial0

Default:0

C++ Type:double

• save_inThe name of auxiliary variables to save this BC's residual contributions to. Everything about that variable must match everything about this variable (the type, what blocks it's on, etc.)

C++ Type:std::vector

Description:The name of auxiliary variables to save this BC's residual contributions to. Everything about that variable must match everything about this variable (the type, what blocks it's on, etc.)

• final0

Default:0

C++ Type:double

• diag_save_inThe name of auxiliary variables to save this BC's diagonal jacobian contributions to. Everything about that variable must match everything about this variable (the type, what blocks it's on, etc.)

C++ Type:std::vector

Description:The name of auxiliary variables to save this BC's diagonal jacobian contributions to. Everything about that variable must match everything about this variable (the type, what blocks it's on, etc.)

### Optional Parameters

• control_tagsAdds user-defined labels for accessing object parameters via control logic.

C++ Type:std::vector

Description:Adds user-defined labels for accessing object parameters via control logic.

• enableTrueSet the enabled status of the MooseObject.

Default:True

C++ Type:bool

Description:Set the enabled status of the MooseObject.

• seed0The seed for the master random number generator

Default:0

C++ Type:unsigned int

Description:The seed for the master random number generator

• implicitTrueDetermines whether this object is calculated using an implicit or explicit form

Default:True

C++ Type:bool

Description:Determines whether this object is calculated using an implicit or explicit form

• use_displaced_meshFalseWhether or not this object should use the displaced mesh for computation. Note that in the case this is true but no displacements are provided in the Mesh block the undisplaced mesh will still be used.

Default:False

C++ Type:bool

Description:Whether or not this object should use the displaced mesh for computation. Note that in the case this is true but no displacements are provided in the Mesh block the undisplaced mesh will still be used.

• vector_tagsresidualThe tag for the vectors this Kernel should fill

Default:residual

C++ Type:MultiMooseEnum

Description:The tag for the vectors this Kernel should fill

• extra_vector_tagsThe extra tags for the vectors this Kernel should fill

C++ Type:std::vector

Description:The extra tags for the vectors this Kernel should fill

• matrix_tagssystem timeThe tag for the matrices this Kernel should fill

Default:system time

C++ Type:MultiMooseEnum

Description:The tag for the matrices this Kernel should fill

• extra_matrix_tagsThe extra tags for the matrices this Kernel should fill

C++ Type:std::vector

Description:The extra tags for the matrices this Kernel should fill