ANALYSIS

Type

AcuSolve Command

Syntax

ANALYSIS {parameters}

Qualifier

This command has no qualifier.

Parameters

title (string) [=""]

Title of the problem. The title, not to exceed 1023 characters, is an optional description of the problem.

sub-title (string) [=""]

Subtitle of the problem. The subtitle is an optional parameter which may be used to further describe the problem. This parameter may not exceed 1023 characters.

input_version or version (string)[="unknown"]

Version of AcuSolve for which this input file was created.

type or mode (enumerated) [=static]

Type of the analysis.

static or steady

Static (steady state) solution.

dynamic or transient

Dynamic (transient) solution.

Description

This command specifies the global analysis information. The title and sub_title parameters allow you to provide a description of the problem. These parameters have no impact on the solution of the problem.

The type parameter specifies the type of analysis being performed, namely static (steady state) or dynamic (transient). In either case, a time marching scheme is used to solve the problem. In the case of static type, the inertia (mass) terms of the conservation equations are only included in the Galerkin part of the finite element weighted residual formulation. This inclusion adds stability to the nonlinear iterations. Other parts of the finite element formulation, such as the least-squares operator, do not include the inertia terms. This exclusion accelerates nonlinear convergence to steady state at the expense of time accuracy. For dynamic type, the inertia terms are included in all the operators of the finite element formulation, in order to preserve time accuracy.

The type parameter alone does not specify the time accuracy of a problem. You also need to set the time integration option via the TIME_INTEGRATION command. In addition, you may need to properly set the number of nonlinear iterations and the nonlinear convergence tolerances via the TIME_SEQUENCE and STAGGER commands, and the time increment options via the TIME_INCREMENT command.

ANALYSIS {
	 title = "Test steady-state solution"
	 sub_title = "8-node brick"
	 type = static
}
TIME_SEQUENCE {
	 convergence_tolerance = 1.e-3
	 min_stagger_iterations = 1
	 max_stagger_iterations = 1
	 ...
}
TIME_INCREMENT {
	 initial_time_increment = 1.e+10
	 auto_time_increment = off
	 local_time_increment = off
}
TIME_INTEGRATION {
 	time_integration_order = first
}

ANALYSIS {
	 title = "Test transient solution"
	 sub_title = "8-node brick"
	 type = dynamic
}
TIME_SEQUENCE {
	 convergence_tolerance = 1.e-3
	 min_stagger_iterations = 2
	 max_stagger_iterations = 3
	 ...
}
TIME_INCREMENT {
	 initial_time_increment = 1.
	 min_time_increment = 0.01
	 max_time_increment = 10.
	 auto_time_increment = on
	 local_time_increment = off
	 ...
}
TIME_INTEGRATION {
	 time_integration_order = second
	 high_frequency_damping_factor = 1.0
}

ANALYSIS {
	title = "Test steady-state solution"
	sub_title = "8-node brick"
	type = static
	input_version = "1.7"
}

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