7.8. Solution Control

This section is referenced in the following other sections

7.8.1. Solution Control Description

Scope: Procedure
Summary: Contains the commands needed to execute an analysis using the arpeggio procedure that uses Solver Control.

begin Solution Control Description Name

   Use System Name

   begin Adaptiveloop Name
   end

   begin Initialize Name
   end

   begin Parameters For
   end

   begin System Name
   end

end Solution Control Description Name

7.8.1.1. Line Commands

Use System

Syntax: Use System Name
Summary: This set the name of which system to use.

Parameter	Value	Default
Name	string	–

7.8.2. System

Scope: Solution Control Description
Summary: This block wraps a solver system for a given name. The NAME parameter is the name used to define the system. There can be more than one system block in the Solver Control Description block. The “use system NAME” line command controls which one is to be used.

begin System Name

   Adapt Mesh For AdaptRegionName Using AdaptBlockName [When WhenExpression]

   Event Name... [ When When-expression  ]

   Output Name [ When When-expression  ]

   Postprocess Aria Region RegionName [Equation System EquationSystemName  | When WhenExpression]

   Simulation Max Global Iterations {=} Number

   Simulation Start Time {=} Number

   Simulation Termination Time {=} Number

   Transfer Name [ When When-expression  ]

   Use Initialize Name

   begin Adaptiveloop Name
   end

   begin Sequential Name
   end

   begin Transient Name
   end

end System Name

7.8.2.1. Line Commands

Adapt Mesh

Syntax: Adapt Mesh For AdaptRegionName Using AdaptBlockName [When WhenExpression]
Summary: Adapt the mesh using the adaptive command block name

Parameter	Value	Default
AdaptRegionName	string	–
AdaptBlockName	string	–
WhenExpression	(expression)	–

Event

Syntax: Event Name… [ When When-expression ]
Summary: Used within a Solver Control block to indicate a single step that has no time associated with it. It can cause a solution transfer between regions or cause something to print.

Parameter	Value	Default
Name	string…	–

Output

Syntax: Output Name [ When When-expression ]
Summary: A Solver Control Output line command which execute a perform I/O on the region.

Parameter	Value	Default
Name	string	–

Postprocess Aria Region

Syntax: Postprocess Aria Region RegionName [Equation System EquationSystemName | When WhenExpression]
Summary: Run Aria Region postprocessors. If specified, only the single equation system’s PPs are run.

Parameter	Value	Default
RegionName	string	–
EquationSystemName	string	–
WhenExpression	(expression)	–

Simulation Max Global Iterations

Syntax: Simulation Max Global Iterations {=} Number
Summary: The Total number of Solves.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Number	integer	–

Simulation Start Time

Syntax: Simulation Start Time {=} Number
Summary: Simulation starting time. (by default 0.0)

Parameter	Value	Default
{=}	{= \| are \| is}	–
Number	real	–

Simulation Termination Time

Syntax: Simulation Termination Time {=} Number
Summary: The drop dead time.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Number	real	–

Transfer

Syntax: Transfer Name [ When When-expression ]
Summary: A Solver Control Transfer line command which executes all transfers defined from the specified region. All transfers with a send region of ‘name’ will be executed.

Parameter	Value	Default
Name	string	–

Use Initialize

Syntax: Use Initialize Name
Summary: This set the name of which initialization to use.

Parameter	Value	Default
Name	string	–

7.8.3. Transient

Scope: Adaptiveloop, System
Summary: This block is used to wrap a time loop.

begin Transient Name

   Advance Name... [ When When-expression  ]

   Adapt Mesh For AdaptRegionName Using AdaptBlockName [When WhenExpression]

   Event Name... [ When When-expression  ]

   Involve Name

   Output Name [ When When-expression  ]

   Postprocess Aria Region RegionName [Equation System EquationSystemName  | When WhenExpression]

   Transfer Name [ When When-expression  ]

   begin Adaptiveloop Name
   end

   begin Nonlinear Name
   end

   begin Subcycle Name
   end

end Transient Name

7.8.3.1. Line Commands

Advance

Syntax: Advance Name… [ When When-expression ]
Summary: Used within a Solver Control block to indicate a single step that advances the solution. The name is that matches the physics.

Parameter	Value	Default
Name	string…	–

Adapt Mesh

Syntax: Adapt Mesh For AdaptRegionName Using AdaptBlockName [When WhenExpression]
Summary: Adapt the mesh using the adaptive command block name

Parameter	Value	Default
AdaptRegionName	string	–
AdaptBlockName	string	–
WhenExpression	(expression)	–

Event

Syntax: Event Name… [ When When-expression ]
Summary: Used within a Solver Control block to indicate a single step that has no time associated with it. It can cause a solution transfer between regions or cause something to print.

Parameter	Value	Default
Name	string…	–

Involve

Syntax: Involve Name
Summary: Specify a physics participant to a coupled problem solved using matrix-free nonlinear.

Parameter	Value	Default
Name	string	–

Output

Syntax: Output Name [ When When-expression ]
Summary: A Solver Control Output line command which execute a perform I/O on the region.

Parameter	Value	Default
Name	string	–

Postprocess Aria Region

Syntax: Postprocess Aria Region RegionName [Equation System EquationSystemName | When WhenExpression]
Summary: Run Aria Region postprocessors. If specified, only the single equation system’s PPs are run.

Parameter	Value	Default
RegionName	string	–
EquationSystemName	string	–
WhenExpression	(expression)	–

Transfer

Syntax: Transfer Name [ When When-expression ]
Summary: A Solver Control Transfer line command which executes all transfers defined from the specified region. All transfers with a send region of ‘name’ will be executed.

Parameter	Value	Default
Name	string	–

7.8.4. Nonlinear

Scope: Sequential, Transient
Summary: This block is used to wrap a nonlinear solve loop.

begin Nonlinear Name

   Advance Name... [ When When-expression  ]

   Adapt Mesh For AdaptRegionName Using AdaptBlockName [When WhenExpression]

   Event Name... [ When When-expression  ]

   Involve Name

   Output Name [ When When-expression  ]

   Postprocess Aria Region RegionName [Equation System EquationSystemName  | When WhenExpression]

   Transfer Name [ When When-expression  ]

   begin Subcycle Name
   end

end Nonlinear Name

7.8.4.1. Line Commands

Advance

Syntax: Advance Name… [ When When-expression ]
Summary: Used within a Solver Control block to indicate a single step that advances the solution. The name is that matches the physics.

Parameter	Value	Default
Name	string…	–

Adapt Mesh

Syntax: Adapt Mesh For AdaptRegionName Using AdaptBlockName [When WhenExpression]
Summary: Adapt the mesh using the adaptive command block name

Parameter	Value	Default
AdaptRegionName	string	–
AdaptBlockName	string	–
WhenExpression	(expression)	–

Event

Syntax: Event Name… [ When When-expression ]
Summary: Used within a Solver Control block to indicate a single step that has no time associated with it. It can cause a solution transfer between regions or cause something to print.

Parameter	Value	Default
Name	string…	–

Involve

Syntax: Involve Name
Summary: Specify a physics participant to a coupled problem solved using matrix-free nonlinear.

Parameter	Value	Default
Name	string	–

Output

Syntax: Output Name [ When When-expression ]
Summary: A Solver Control Output line command which execute a perform I/O on the region.

Parameter	Value	Default
Name	string	–

Postprocess Aria Region

Syntax: Postprocess Aria Region RegionName [Equation System EquationSystemName | When WhenExpression]
Summary: Run Aria Region postprocessors. If specified, only the single equation system’s PPs are run.

Parameter	Value	Default
RegionName	string	–
EquationSystemName	string	–
WhenExpression	(expression)	–

Transfer

Syntax: Transfer Name [ When When-expression ]
Summary: A Solver Control Transfer line command which executes all transfers defined from the specified region. All transfers with a send region of ‘name’ will be executed.

Parameter	Value	Default
Name	string	–

7.8.5. Subcycle

Scope: Nonlinear, Transient
Summary: This block is used to wrap a subcycle time loop.

begin Subcycle Name

   Advance Name... [ When When-expression  ]

   Adapt Mesh For AdaptRegionName Using AdaptBlockName [When WhenExpression]

   Event Name... [ When When-expression  ]

   Involve Name

   Output Name [ When When-expression  ]

   Postprocess Aria Region RegionName [Equation System EquationSystemName  | When WhenExpression]

   Transfer Name [ When When-expression  ]

end Subcycle Name

7.8.5.1. Line Commands

Advance

Syntax: Advance Name… [ When When-expression ]
Summary: Used within a Solver Control block to indicate a single step that advances the solution. The name is that matches the physics.

Parameter	Value	Default
Name	string…	–

Adapt Mesh

Syntax: Adapt Mesh For AdaptRegionName Using AdaptBlockName [When WhenExpression]
Summary: Adapt the mesh using the adaptive command block name

Parameter	Value	Default
AdaptRegionName	string	–
AdaptBlockName	string	–
WhenExpression	(expression)	–

Event

Syntax: Event Name… [ When When-expression ]
Summary: Used within a Solver Control block to indicate a single step that has no time associated with it. It can cause a solution transfer between regions or cause something to print.

Parameter	Value	Default
Name	string…	–

Involve

Syntax: Involve Name
Summary: Specify a physics participant to a coupled problem solved using matrix-free nonlinear.

Parameter	Value	Default
Name	string	–

Output

Syntax: Output Name [ When When-expression ]
Summary: A Solver Control Output line command which execute a perform I/O on the region.

Parameter	Value	Default
Name	string	–

Postprocess Aria Region

Syntax: Postprocess Aria Region RegionName [Equation System EquationSystemName | When WhenExpression]
Summary: Run Aria Region postprocessors. If specified, only the single equation system’s PPs are run.

Parameter	Value	Default
RegionName	string	–
EquationSystemName	string	–
WhenExpression	(expression)	–

Transfer

Syntax: Transfer Name [ When When-expression ]
Summary: A Solver Control Transfer line command which executes all transfers defined from the specified region. All transfers with a send region of ‘name’ will be executed.

Parameter	Value	Default
Name	string	–

7.8.6. Sequential

Scope: Adaptiveloop, System
Summary: This block is used to wrap a sequential solution. It is used to wrap a sequence of Non-Linear or pseudo time solve step solves.

begin Sequential Name

   Advance Name... [ When When-expression  ]

   Adapt Mesh For AdaptRegionName Using AdaptBlockName [When WhenExpression]

   Event Name... [ When When-expression  ]

   Involve Name

   Output Name [ When When-expression  ]

   Postprocess Aria Region RegionName [Equation System EquationSystemName  | When WhenExpression]

   Transfer Name [ When When-expression  ]

   begin Adaptiveloop Name
   end

   begin Nonlinear Name
   end

end Sequential Name

7.8.6.1. Line Commands

Advance

Syntax: Advance Name… [ When When-expression ]
Summary: Used within a Solver Control block to indicate a single step that advances the solution. The name is that matches the physics.

Parameter	Value	Default
Name	string…	–

Adapt Mesh

Syntax: Adapt Mesh For AdaptRegionName Using AdaptBlockName [When WhenExpression]
Summary: Adapt the mesh using the adaptive command block name

Parameter	Value	Default
AdaptRegionName	string	–
AdaptBlockName	string	–
WhenExpression	(expression)	–

Event

Syntax: Event Name… [ When When-expression ]
Summary: Used within a Solver Control block to indicate a single step that has no time associated with it. It can cause a solution transfer between regions or cause something to print.

Parameter	Value	Default
Name	string…	–

Involve

Syntax: Involve Name
Summary: Specify a physics participant to a coupled problem solved using matrix-free nonlinear.

Parameter	Value	Default
Name	string	–

Output

Syntax: Output Name [ When When-expression ]
Summary: A Solver Control Output line command which execute a perform I/O on the region.

Parameter	Value	Default
Name	string	–

Postprocess Aria Region

Syntax: Postprocess Aria Region RegionName [Equation System EquationSystemName | When WhenExpression]
Summary: Run Aria Region postprocessors. If specified, only the single equation system’s PPs are run.

Parameter	Value	Default
RegionName	string	–
EquationSystemName	string	–
WhenExpression	(expression)	–

Transfer

Syntax: Transfer Name [ When When-expression ]
Summary: A Solver Control Transfer line command which executes all transfers defined from the specified region. All transfers with a send region of ‘name’ will be executed.

Parameter	Value	Default
Name	string	–

7.8.7. Initialize

Scope: Solution Control Description
Summary: This block wraps a initializer for a given name. The NAME parameter is the name used to define the initialization block. There can be more than one initialize block in the Solver Control Description block. The “use initialize NAME” line command controls which one is to be used.

begin Initialize Name

   Advance Name... [ When When-expression  ]

   Event Name... [ When When-expression  ]

   Involve Name

   Transfer Name [ When When-expression  ]

end Initialize Name

7.8.7.1. Line Commands

Advance

Syntax: Advance Name… [ When When-expression ]
Summary: Used within a Solver Control block to indicate a single step that advances the solution. The name is that matches the physics.

Parameter	Value	Default
Name	string…	–

Event

Syntax: Event Name… [ When When-expression ]
Summary: Used within a Solver Control block to indicate a single step that has no time associated with it. It can cause a solution transfer between regions or cause something to print.

Parameter	Value	Default
Name	string…	–

Involve

Syntax: Involve Name
Summary: Specify a physics participant to a coupled problem solved using matrix-free nonlinear.

Parameter	Value	Default
Name	string	–

Transfer

Syntax: Transfer Name [ When When-expression ]
Summary: A Solver Control Transfer line command which executes all transfers defined from the specified region. All transfers with a send region of ‘name’ will be executed.

Parameter	Value	Default
Name	string	–

7.8.8. Parameters For

Scope: Solution Control Description
Summary: A Solver Control PARAMETERS block to set up control data for the SC_type parameter. Inside this block one sets the time step parameters or nonlinear parameters.

begin Parameters For

   Converged When Convergence-expression

   Incremental Number Of Steps {=} Number

   Initial Deltat {=} Number

   Number Of Adaptivity Steps {=} Number

   Number Of Steps {=} Number

   Reinitialize Transient

   Start Time {=} Number

   Suppress Output From Nonlinear Loop

   Termination Time {=} Number

   Time Step Quantum {=} TimeStepQuantum

   Time Step Style TimeStepStyle...

   Total Change In Time {=} Number

   begin Parameters For Aria Region RegionName
   end

end Parameters For

7.8.8.1. Line Commands

Converged When

Syntax: Converged When Convergence-expression
Summary: Set the convergence expression.

Parameter	Value	Default
Convergence-expression	(expression)	–

Incremental Number Of Steps

Syntax: Incremental Number Of Steps {=} Number
Summary: The incremental number steps to run the time for nonlinear loop. Number of time steps to run after restarting. NUMBER OF STEPS is total number of steps to run

Parameter	Value	Default
{=}	{= \| are \| is}	–
Number	integer	–

Initial Deltat

Syntax: Initial Deltat {=} Number
Summary: Assign an initial delta T

Parameter	Value	Default
{=}	{= \| are \| is}	–
Number	real	–

Number Of Adaptivity Steps

Syntax: Number Of Adaptivity Steps {=} Number
Summary: The number steps to run the time or nonlinear loop

Parameter	Value	Default
{=}	{= \| are \| is}	–
Number	integer	–

Number Of Steps

Syntax: Number Of Steps {=} Number
Summary: The number steps to run the time for nonlinear loop

Parameter	Value	Default
{=}	{= \| are \| is}	–
Number	integer	–

Reinitialize Transient

Syntax: Reinitialize Transient
Summary: Reset time and re-initialize regions each step of the adaptivity loop.

Start Time

Syntax: Start Time {=} Number
Summary: Assign a start time.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Number	real	–

Suppress Output From Nonlinear Loop

Syntax: Suppress Output From Nonlinear Loop
Summary: Specify that the nonlinear loop will not output. Output will be handled by calls outside of the nonlinear loop (such as an additional advance region call).

Termination Time

Syntax: Termination Time {=} Number
Summary: Assign a final time to stop

Parameter	Value	Default
{=}	{= \| are \| is}	–
Number	real	–

Time Step Quantum

Syntax: Time Step Quantum {=} TimeStepQuantum
Summary: Set the time stepping quantum time for SNAP style stepping.

Parameter	Value	Default
{=}	{= \| are \| is}	–
TimeStepQuantum	real	–

Time Step Style

Syntax

Time Step Style TimeStepStyle…

Summary

Set the time stepping style.

When CLIP is specified, the time step size will be clipped at the last step of the transient loop so that it ends at the transient loop’s end time. If clip is not specified, the last time is allowed to exceed to the transient loop’s end time and the following transient loop will start at the exceeded end time.

When SNAP is specified, the time step is broken down into “quantum” time units. By default this quantum time is 12 orders of magnitude down from the difference between the start and end time for the transient loop. This value can be overridden using the TIME STEP QUANTUM line command. All time values are “snapped” to multiples of the quantum time by rounding to the nearest quantum multiple.

Parameter	Value	Default
TimeStepStyle	{clip \| noclip \| nosnap \| snap}	CLIP NOSNAP

Total Change In Time

Syntax: Total Change In Time {=} Number
Summary: Use this number and the initial time to compute termination time.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Number	real	–

7.8.9. Parameters For Aria Region

Scope: Parameters For
Summary: Defines region specific time stepping data

begin Parameters For Aria Region RegionName

   Allow Order Switch For HowMany Steps

   Courant Limit {=} Courant_limit

   Fail Time Step On Bad Aztec Solver Status

   Fail Time Step When Time Step Size Ratio Is Below Ratio

   Failed Time Step Size Ratio {=} Ratio

   Initial Nonlinear Residual Tolerance For Time Step Control {=} tolerance

   Initial Time Step Size {=} Dt

   Interface Courant Limit {=} Interface Courant_limit

   Known Time Discontinuities {=} times...

   Limit Solution Increment Field_name {=} Value [ Action  ]

   Maximum Acceptable Linear Residual Ratio {=} Ratio

   Maximum Consecutive Time Step Failures {=} NumFails

   Maximum Global Var Limit Encore_name {=} Value [ Action  ]

   Maximum Linear Residual Ratio {=} Ratio

   Maximum Solution Limit Field_name {=} Value [ Action  ]

   Maximum Time Step Size {=} Dt

   Maximum Time Step Size Ratio {=} Ratio

   Mesh Courant Limit {=} Mesh Courant_limit

   Minimum Global Var Limit Encore_name {=} Value [ Action  ]

   Minimum Resolved Time Step Size {=} Dt

   Minimum Solution Limit Field_name {=} Value [ Action  ]

   Minimum Time Step Size {=} Dt

   Predictor Order {=} order

   Predictor-Corrector Begin After Step {=} Step

   Predictor-Corrector Field Normalization {on} Field_name {=} {courant | max | mesh | none | user} [ Scaling  ]

   Predictor-Corrector Normalization {=} {courant | max | mesh | none | user} [ Scaling  ]

   Predictor-Corrector Tolerance {=} Predictor_corrector_tolerance

   Reset Initial Time Step Size

   Slope Of Time Step Size {=} slope

   Stop When Initial Nonlinear Residual Is Below Tol

   Time Integration Method {=} {average_acceleration | backward_euler | bdf2 | first_order | midpoint_rule | second_order}

   Time Step Variation {=} {adaptive | fixed}

   Use Initial Nonlinear Residual For Time Step Control {=} {false | no | off | on | true | yes}

end Parameters For Aria Region RegionName

7.8.9.1. Line Commands

Allow Order Switch For

Syntax: Allow Order Switch For HowMany Steps
Summary: Allow the switching of time integration order from a higher order to first order.
Description: This command allows for the switching of a higher order method to a first order method for a specified number of steps in order to improve the robustness of the simulation especially in the region of discontinuities such as chemistry shutoff. This command is mostly useful in the context of a SECOND_ORDER time integration method.

Parameter	Value	Default
HowMany	integer	–

Courant Limit

Syntax: Courant Limit {=} Courant_limit
Summary: The Courant Number limit. A value of 0.0 denotes INACTIVE.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Courant_limit	real	0.0

Fail Time Step On Bad Aztec Solver Status

Syntax: Fail Time Step On Bad Aztec Solver Status
Summary: This command is deprecated and no longer has any effect.

Fail Time Step When Time Step Size Ratio Is Below

Syntax

Fail Time Step When Time Step Size Ratio Is Below Ratio

Summary

Specify lower bound for adaptive time step size ratio failure criteria.

If the adaptive time step size ratio falls below this value, Aria will fail the time step. This criteria is specified in terms of the size of the time step size ratio, defined as $dt_{n+1}/dt_{n}$ . When the adaptive time stepper senses the time step being cut back too much, the time step fails. The default is equal to the FAILED TIME STEP SIZE RATIO.

In simulations where the predicted time step is reduced substantially, a time step may fail repeatedly on this criterion. In that event the user may want to set this Ratio to a small positive value, possibly even zero.

Parameter	Value	Default
Ratio	real	–

Failed Time Step Size Ratio

Syntax

Failed Time Step Size Ratio {=} Ratio

Summary

Specifies the factor used to cut the time step size when a step fails.

When a time step fails, the time step size is reduced by this factor.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Ratio	real	0.5

Initial Nonlinear Residual Tolerance For Time Step Control

Syntax: Initial Nonlinear Residual Tolerance For Time Step Control {=} tolerance
Summary: Set initial nonlinear residual tolerance for time step control.
Description: Sets the tolerance on the initial nonlinear residual to be used for time step control.

Parameter	Value	Default
{=}	{= \| are \| is}	–
tolerance	real	1.0

Initial Time Step Size

Syntax

Initial Time Step Size {=} Dt

Summary

Specifies the initial time step size for the given parameter block.

The initial time step size should always be specified for FIXED time stepping and for the starting time block of ADAPTIVE time stepping. When no other command lines affecting timestep are provided in the time step parameter block the time step will remain constant over the time extent of the parameter block.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Dt	real	–

Interface Courant Limit

Syntax: Interface Courant Limit {=} Interface Courant_limit
Summary: The Interface Courant Number limit. Applies to both diffuse level set and CDFEM problems. A value of 0.0 denotes INACTIVE.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Interface Courant_limit	real	0.0

Known Time Discontinuities

Syntax: Known Time Discontinuities {=} times…
Summary: Specifies known time discontinuities in the solution that the adaptive time stepping procedure must capture.
Description: Allows user to specify certain times that the adaptive time stepper must solve at because the solution is known to have a discontinuity there. This is useful for problems where the boundary conditions change suddenly for example.

Parameter	Value	Default
{=}	{= \| are \| is}	–
times	real…	–

Limit Solution Increment

Syntax

Limit Solution Increment Field_name {=} Value [ Action ]

Summary

Provides user control for limiting maximum change in a chosen solution Field over a timestep. When action is PREDICT a time step estimation is computed based upon the predicted solution change. When action is FAIL_STEP the time step is still predicted but the the time step will also fail if the suggested solution increment is exceeded.

Description

This command allows one to roughly specify the maximum magnitude that a solution Field can change within a step. A solution increment is estimated based upon the maximum change in the Field in the previous timestep and the proposed adaptive timestep. When the specified value of maximum solution increment is exceeded, the proposed adaptive timestep is reduced in an attempt to limit the solution increment.

One command line should be supplied for each solution Field one wishes to restrict. The restriction is applied directly to the solution Field values, no scaling is invoked.

Parameter	Value	Default
Field_name	string	–
{=}	{= \| are \| is}	–
Value	real	REAL_MAX

Maximum Acceptable Linear Residual Ratio

Syntax

Maximum Acceptable Linear Residual Ratio {=} Ratio

Summary

Specifies a failure criterion for a nonlinear step based on the ratio of the final linear residual to a nonlinear residual.

The ratio must be greater than zero and less than one.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Ratio	real	–

Maximum Consecutive Time Step Failures

Syntax: Maximum Consecutive Time Step Failures {=} NumFails
Summary: Specifies a maximum consecutive of time step failures before a simulation is terminated. This prevents the application from continued cutback of the time step when recovery of the solution is unlikely.

Parameter	Value	Default
{=}	{= \| are \| is}	–
NumFails	integer	20

Maximum Global Var Limit

Syntax: Maximum Global Var Limit Encore_name {=} Value [ Action ]
Summary: This command allows the simulation to continue only when the given Encore variable is lower than a certain magnitude. Inclusion of the optional argument RETRY will cause the solution step to fail and the time step to be reduced. This sequence will be carried out a maximum of three steps, after which the simulation will be terminated.
Description: This command allows the simulation to continue only when the given Encore variable is lower than a certain magnitude.

Parameter	Value	Default
Encore_name	string	–
{=}	{= \| are \| is}	–
Value	real	–

Maximum Linear Residual Ratio

Syntax

Maximum Linear Residual Ratio {=} Ratio

Summary

Specifies a failure criterion for a nonlinear step based on the ratio of a nonlinear residual to the initial nonlinear residual.

NOTE: The linear residual is not utilized with this check.

This criteria is not be used unless requested by the user.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Ratio	real	–

Maximum Solution Limit

Syntax

Maximum Solution Limit Field_name {=} Value [ Action ]

Summary

Provides user control for limiting maximum value of a Field solution over a time step. Optional parameters are continue or terminate. When a step fails the step will be cut back and and the optional behavior is invoked when three consecutive fails have occurred. Default behavior is to terminate.

Description

This command allows one to restrict the maximum magnitude that a solution Field can achieve within a simulation by causing the time step to fail when the Field value exceeds a user specified magnitude.

Oftentimes the maximum value will be tied to an event that occurs at a particular magnitude of the Field. This command can be used to impose a different solution behavior when this magnitude of the Field is realized by forcing a failure of the solution step. When the step is failed due to solution limit then cutback of the time step is allowed to occur for two consecutive steps. If the time step is cut back a third time in succession, the specified action of the command will be invoked.

By default the simulation will terminate when the maximum value is reached. If the optional argument is “continue” then time step failure will be over-ridden and the solution sequence will continue, presumably evolving toward lower magnitude values of the Field. This behavior may enable one to overcome large reductions in time step at discontinuous events which may occur for maximum values of the Field.

Parameter	Value	Default
Field_name	string	–
{=}	{= \| are \| is}	–
Value	real	REAL_MAX

Maximum Time Step Size

Syntax

Maximum Time Step Size {=} Dt

Summary

Specifies the maximum time step size for this parameter block.

The time step will not be allowed to exceed this value, regardless of adaptive time step selection and regardless of time step requests for other regions (for loosely coupled simulations).

Parameter	Value	Default
{=}	{= \| are \| is}	–
Dt	real	REAL_MAX

Maximum Time Step Size Ratio

Syntax

Maximum Time Step Size Ratio {=} Ratio

Summary

Specifies the maximum allowable growth rate of the adaptive time step size.

If the time step selection computes a new time step size that exceeds the previous step size by more than this amount, then the new step size is limited to the product of this factor and the previous step size.

The default is 2.0 for FIRST_ORDER and SECOND_ORDER integration methods.

For BDF2 a value of 2.4 is imposed to enforce stability of the integrator.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Ratio	real	2.0/2.4

Mesh Courant Limit

Syntax: Mesh Courant Limit {=} Mesh Courant_limit
Summary: The Mesh Courant Number limit. Applies to problems with mesh motion. CFL condition is applied based on normal mesh velocities at the boundary with the length scale taken as the element volume divided by the element surface area. A value of 0.0 denotes INACTIVE.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Mesh Courant_limit	real	0.0

Minimum Global Var Limit

Syntax: Minimum Global Var Limit Encore_name {=} Value [ Action ]
Summary: This command allows the simulation to continue only when the given Encore variable is higher than a certain magnitude. Inclusion of the optional argument, RETRY, will cause the solution step to fail and the time step to be reduced. This sequence will be carried out a maximum of three steps, after which the simulation will be terminated.
Description: This command allows the simulation to continue only when the given Encore variable is higher than a certain magnitude.

Parameter	Value	Default
Encore_name	string	–
{=}	{= \| are \| is}	–
Value	real	–

Minimum Resolved Time Step Size

Syntax

Minimum Resolved Time Step Size {=} Dt

Summary

Specifies the minimum resolved time step size. If the time step size lies below this value, the step will not fail when the time step size ratio falls too low.

This setting serves as a floor value since the adaptive time stepper will not select a time step size below this value, and any predictor-corrector errors are neglected when the time step size falls below this value.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Dt	real	0.0

Minimum Solution Limit

Syntax

Minimum Solution Limit Field_name {=} Value [ Action ]

Summary

Provides user control for limiting minimum value of a Field solution over a time step. Optional parameters are continue or terminate. When a step fails the step will be cut back and and the optional behavior is invoked when three consecutive fails have occurred. Default behavior is to terminate.

Description

By default the solution minimum limit for all Fields is not active. This command allows one to restrict the minimum magnitude that a solution Field can achieve within a simulation by causing the time step to fail when the Field value goes below a user specified value

See MAXIMUM SOLUTION LIMIT command for more info.

Parameter	Value	Default
Field_name	string	–
{=}	{= \| are \| is}	–
Value	real	–

Minimum Time Step Size

Syntax: Minimum Time Step Size {=} Dt
Summary: Specifies the minimum time step size for the given parameter block. The time step will not be allowed to fall below this value, regardless of adaptive time step selection and regardless of time step requests from other regions (for loosely coupled simulations).

Parameter	Value	Default
{=}	{= \| are \| is}	–
Dt	real	1.0e-16

Predictor Order

Syntax

Predictor Order {=} order

Summary

Specifies the order of the extrapolation used to predict the solution in transient simulations. An order of 0 corresponds to no extrapolation, instead copying the previous solution into the predicted solution.

Description

This command sets the order of extrapolation in the predictor for transient problems. A value of 0 basically turns off the extrapolation, and instead copies to old solution to the predicted solution.

ThePREDICTOR ORDER defaults to 0 for problems if Gas Dynamics equations are defined. Otherwise, it is set to the order of the time integrator for the current time block i.e 1 for first order and 2 for second order

Parameter	Value	Default
{=}	{= \| are \| is}	–
order	integer	–

Predictor-Corrector Begin After Step

Syntax

Predictor-Corrector Begin After Step {=} Step

Summary

Specifies after which solution step the Predictor-Corrector timestep calculation will begin to be used in computing an adaptive timestep. Predictor error will always be computed but will not actually be used until the prescribed step is reached.

Default value is 2 for first-order time integration and 3 for second-order time integration. Thus for first-order time integration, a candidate predictor-corrector timestep could appear in step 3.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Step	integer	2 / 3

Predictor-Corrector Field Normalization

Syntax

Predictor-Corrector Field Normalization {on} Field_name {=} {courant | max | mesh | none | user} [ Scaling ]

Summary

Allows user to change the predictor-corrector normalization type for a given field variable separately from the global option.

Description

Allows user to change the predictor-corrector normalization type for a given field variable separately from the global option.

Normalization types are:

NONE: Scale by unity
MAX (default): Scale by the maximum field value
USER: Scale by a constant (user-supplied) value

Parameter	Value	Default
{on}	{@ \| at \| for \| in \| on \| over}	–
Field_name	string	–
{=}	{= \| are \| is}	–
Norm_type	{courant \| max \| mesh \| none \| user}	MAX

Predictor-Corrector Normalization

Syntax

Predictor-Corrector Normalization {=} {courant | max | mesh | none | user} [ Scaling ]

Summary

Provides the ability to specify how the predictor-corrector error is normalized.

Currently supported values are MAX, NONE, and USER. If desired, L2 could be added easily. A possibly better method would be to allow user-specified scales for the variables but that’s not yet supported.

The reason for allowing NONE (or even better, a user-specified scale) is to better handle problems that involve something that is zero-based with finite changes. This can happen in ALE problems where the adaptive time stepper is overly restrictive initially when the displacements are all nearly zero, but growing to some finite value.

Default is MAX.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Normalization	{courant \| max \| mesh \| none \| user}	MAX

Predictor-Corrector Tolerance

Syntax

Predictor-Corrector Tolerance {=} Predictor_corrector_tolerance

Summary

Specifies the tolerance for the difference between the predicted solution and the implicitly solved corrector solution used in adaptive time step selection.

The adaptive time step selection formula is

$\label{eqn:adapt_dt} \Delta t_{n+1} = \Delta t_n \left(b \frac{\epsilon}{d_{n+1}} \right)^m$

where $\Delta t_n\equiv t_{n+1}-t_n$ is the time step size from the most recent solution, $\Delta t_{n+1}\equiv t_{n+2}-t_{n+1}$ is the new time step size, $\epsilon$ is the predictor-corrector tolerance and $d_{n+1}$ is the norm of the difference between the predicted and actual solutions at time $t_{n+1}$ . For first order time integration $m=1/2$ and $b=2$ . For second order time integration $m=1/3$ and $b=3(1+\Delta t_{n-1} / \Delta t_n)$ . See [57].

Parameter	Value	Default
{=}	{= \| are \| is}	–
Predictor_corrector_tolerance	real	0.001

Reset Initial Time Step Size

Syntax: Reset Initial Time Step Size
Summary: Enforce use of initial time step size specification.
Description: When using adaptive time stepping with restart the initial time step size is taken from the restart file rather than the INITIAL TIME STEP SIZE specification. This choice of time step can be problematic if one wishes to change model features at the beginning of a restart. This command forces the time step selection to respect an initial time step size specification.

Slope Of Time Step Size

Syntax: Slope Of Time Step Size {=} slope
Summary: Specifies the linear growth rate of the time step size for the given parameter block. The time step size will grow by this amount at each step unless limited by other factors.

Parameter	Value	Default
{=}	{= \| are \| is}	–
slope	real	–

Stop When Initial Nonlinear Residual Is Below

Syntax: Stop When Initial Nonlinear Residual Is Below Tol
Summary: Specify time block termination criteria based upon nonlinear residual value. If the initial nonlinear residual falls below this value, Aria will end the time block. This is useful for obtaining pseudo-transient solutions of steady-state problems.

Parameter	Value	Default
Tol	real	–

Time Integration Method

Syntax

Time Integration Method {=} {average_acceleration | backward_euler | bdf2 | first_order | midpoint_rule | second_order}

Summary

Specifies the order of time integration.

Valid options are BACKWARD_EULER, FIRST_ORDER, SECOND_ORDER, BDF2, MIDPOINT_RULE and AVERAGE_ACCELERATION.

Note that the stability criteria of BDF2 will restrict the timestep growth by imposing a MAXIMUM TIME STEP SIZE RATIO of 2.14.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Time_integration_method	{average_acceleration \| backward_euler \| bdf2 \| first_order \| midpoint_rule \| second_order}	–

Time Step Variation

Syntax

Time Step Variation {=} {adaptive | fixed}

Summary

Specifies how the time step sizes are to be derived. Choose between FIXED and ADAPTIVE time step selection methods.

When the time step is ADAPTIVE the time step is determined using a predictor-corrector error criteria.

Parameter	Value	Default
{=}	{= \| are \| is}	–
Time_step_variation	{adaptive \| fixed}	–

Use Initial Nonlinear Residual For Time Step Control

Syntax: Use Initial Nonlinear Residual For Time Step Control {=} {false | no | off | on | true | yes}
Summary: Enable use of initial nonlinear residual as an error estimate to control timestep for loosely coupled problems.
Description: When enabled this option will treat the initial non-linear residual as a proxy for the error in region-region convergence for loosely coupled problems. The time step will be controlled using a predictor-corrector like algorithm.

Parameter	Value	Default
{=}	{= \| are \| is}	–
enable	{false \| no \| off \| on \| true \| yes}	–