zone apply command

Syntax

zone apply keyword <range>

Primary keywords:

force    force-x    force-y    force-z    source    well

Create or modify zone apply conditions.

Note

[1] Zone nomenclature in FLAC varies from 2D to 3D.

This command is used to apply conditions to the volume represented by zones — i.e., body forces or fluid/thermal sources. For application of boundary conditions on surfaces represented by zone faces, see the zone face apply command. The user must specify the condition type, the numerical value, optional modifiers, and an optional range over which the condition is to be applied. If no range is specified, then the command applies to the entire model. Removal of zone conditions is done with a separate command — see zone apply-remove.

After the supplied condition’s value (f or v), an optional modifier keyword can be used to modulate the supplied value. The position of the modifier in the command is indicated below by [applyblock]; the valid modifier keywords are found in the Keyword Block section below that follows the principal keywords. The modifiers can be used to vary the value of the applied condition in both time and space.

All values are considered to be per unit volume.

Apply conditions that conflict with currently existing ones will overwrite them.

force v [applyblock]

Apply all components of the body force, per unit volume, to all zones in the range.

force-x f [applyblock]

Apply the \(x\)-component of the body force, per unit volume, to all zones in the range.

force-y f [applyblock]

Apply the \(y\)-component of the body force, per unit volume, to all zones in the range.

force-z f (3D ONLY) [applyblock]

Apply the \(z\)-component of the body force, per unit volume, to all zones in the range.

source f [applyblock]

Apply a heat-generating source, f, as a volume source of the specified strength (e.g., in W/m³ ) in each zone in the specified range. When a new source is applied to a zone with an existing source, the new source strength replaces the existing source strength.

Decay of the heat source over time can be represented by applying one of the available modifiers.

Note: This keyword is only available for the thermal model option.

well f [applyblock]

Apply a volume rate of flow, f (i.e., fluid volume per zone volume per unit time), for each zone in the specified range (f > 0 for inflow).

Note: A fluid flow model must exist for this command to work.

zone apply Keyword Block

The following keywords may be used to modify the base value supplied. force, force-x, force-y, force-z, source and well.

fish s

Specify a multiplier that is a FISH function named s. See the section FISH Callback Events for a discussion of FISH callbacks.

The return value of this FISH function is multiplied by the base value (including gradient) over all zones included in this apply condition. So a return value of 1.0 will apply the base value provided, and a return value of 0.0 will effectively remove it. This function will be called every step.

If the apply condition requires a vector value, this function should also return a vector.

fish-local s

Specify a multiplier that is a FISH function named s, which is applied separately to each individual zone affected by this apply condition. See the section FISH Callback Events for a discussion of FISH callbacks.

This function must take two arguments, the first of which will be a pointer to the specific zone. The second argument is not used. This allows an apply condition to vary over time as well as space. The returned value of this FISH function is multiplied by the base value (including gradient) on the specific zone supplied. So a return value of 1.0 will apply the base value provided, and a return value of 0.0 will effectively remove it. This function will be called every step for every zone included in the apply condition.

If the apply condition requires a vector value, this function should also return a vector.

gradient v <origin v >

Apply a gradient in space to the scalar-value provided. The position used in this calculation is the zone centroid. Another way of assigning a linear gradient is with the vary modifier.

servo keyword ...

Use a servo tied to the mechanical convergence ratio to control the magnitude of the applied condition. This can be used to maintain, gradually ramp up, or gradually reduce apply conditions while maintaining a quasi-static response. By default the multiplier will start at 0.001, and will gradually increase to 1.0 as the convergence ratio falls below 2e-3, and decrease if it rises above 1e-2. The following keywords are available to control the servo response:

latency i

Set the minimum number of steps that must pass since the last servo adjustment before the next one occurs. This can keep the servo from over-controlling in the initial response to an adjustment. The default value is 1.

lower-bound f

Set the lower mechanical convergence ratio value. If the current ratio falls below this value, the current multiplier will be multiplied by the lower-multiplier. The default value is 2e-3.

lower-multiplier f

Set the value multiplier to f if the current ratio falls below the lower-bound. The default value is 0.975.

maximum f

Set the maximum value allowed for the current multiplier. The default value is 1.0.

minimum f

Set the minimum value allowed for the current multiplier. The default value is 0.001.

ramp

Sets the servo into ramp mode. This means that the current multiplier is not allowed to go down, the value will only increase. This is useful to gradually increase an applied condition to its full value. See also the reduce keyword.

ratio keyword

Set the mechanical convergence ratio to user for comparison against the lower-bound and upper-bound values. By default this is the current value assigned by the zone ratio command (for which the default setting is average). See the zone ratio command for definitions. The available keywords are:

average

Specify use of the average mechanical force ratio.

convergence

Specify use of the maximum convergence value.

local

Specify use of the local mechanical force ratio.

maximum

Specify use of the maximum mechanical force ratio.

reduce

Set the servo into reduce mode. In this mode the starting value of the current multiplier is 1.0, and the minimum value is set to 0.0. When the current ratio falls below lower-bound the current multiplier is reduced by the upper-multiplier. The current multiplier is never increased. This is useful to gradually decrease an applied condition to zero.

upper-bound f

Set the upper mechanical convergence ratio value. If the current ratio rises above this value, the current multiplier will be multiplier by the upper-multiplier. The default value is 1e-2.

upper-multiplier f

Multiply the value by f if the current ratio rises above the upper-bound. The default value is 1.01.

table s <time keyword>

Specify a value multiplier that is thee table named s. By default, the \(x\)-value of the table is the step number. The returned value of this table is multiplied by the base value (including gradient) over all zones included in this apply condition. So a return value of 1.0 will apply the base value provided, and a return value of 0.0 will effectively remove it. The table lookup will be performed every step. The time scale for the \(x\)-axis can also be selected by giving the time keyword followed by one of the following options:

step

creep

dynamic

fluid

mechanical

thermal

vary v

Apply a linear variation to the scalar-value provided. The position used in this calculation is the zone centroid. Another way of assigning a linear gradient is with the gradient modifier.

See also

zone apply-remove

Endnote

[1]

In FLAC2D and FLAC3D nomenclature, the following variants/equivalents are observed:

• Zone faces refer to zone surface faces in 3D or zone edges (lines connecting gridpoints) in 2D

• Zone edges in 3D do not have a 2D equivalent

• Zones have volume (3D) or area (2D)

• Zone faces have surface area (3D) or face length (2D)