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FREQUENCY_CUTOFF

Solution control and techniques

Beta command

This command is in the beta stage and the format may change over time.

*FREQUENCY_CUTOFF
"Optional title"
coid
entype, enid, $\Delta t_{target}$, $sf_{cap}$, $t_{start}$, $t_{end}$, no_regms

Parameter definition

Variable
Description
coid
Command ID
entype
Entity type
options: P, PS, ALL
enid
Entity identification number
$\Delta t_{target}$
Target time step size (scalar value of function of time)
options: scalar or fcn
$sf_{cap}$
Maximum increase of time step size (scale factor)
options: scalar or fcn
default: not used
$t_{start}$
Activation time
$t_{end}$
Deactivation time
no_regms
Flag to disable regular mass scaling of the parts that are treated by this command (see $\Delta t_{min}$ in TIME)
options:
0 $\rightarrow$ regular mass scaling is allowed
1 $\rightarrow$ regular mass scaling is deactivated

Description

The primary purpose of this command is to allow for larger time steps in quasi-static processes. This is achieved by suppressing angular frequencies $\omega \gt 2 / \Delta t_{target}$.

The algorithm is approximative and frequencies below the threshold value will, to some extent, be affected. If used with care, the command can also be applied to increase the time step size in dynamic events that are dominated by the lowest natural frequencies.

$sf_{cap}$ is an optional scale factor, defining an upper cap for the time step size.

$\displaystyle{ \Delta t = \mathrm{min} \left( \Delta t_{target}, sf_{cap} \Delta t_c \right) }$

where $\Delta t$ is the actual time step size and $\Delta t_c$ is the critical time step size without frequency suppression.