# AFLR Point Spacing/Distribution Function Parameters

The following are AFLR parameters used to control how the distribution function for volume nodes is calculated.

**dfmax**

Maximum distribution function.

The distribution function specifies the point spacing in the field. If dfmax < 0 then do not limit the maximum distribution function.

If dfmax = 0 then limit the maximum distribution function to the maximum value determined from the boundary surface grid.

If dfmax > 0 then limit the maximum distribution function to dfmax. AFLR2/AFLR3 parameter.

default=-1 min=-1 max=1e+19

**mlsr**

Length scale ratio improvement flag.

Source nodes can be generated to improve the minimum length scale ratio (LSRatio), minimum node spacing over distance between boundaries.

If mlsr = 0 then do not use length scale ratio (LSRatio) improvement.

If mlsr = 1 then use length scale ratio (LSRatio) improvement. In this case, source nodes are created on a nested set of embedded rectangular surfaces.

default=0 min=0 max=1

**cinlpp**

Initial point placement factor.

During grid generation large elements that have all edges larger than the distribution function (local point spacing) are subdivided using centroid point placement.

Elements that have a ratio of local spacing over minimum edge length less than cinlpp are subdivided.

A value of cinlpp=0 will turn off initial point placement and standard point placement will be used from the start.

default=0.1 min=0 max=0.5

**lsrcdf**

LSRatio improvement limit factor.

Source nodes are generated to improve the minimum length scale ratio (LSRatio), minimum node spacing over distance between boundaries.

The spacing calculated for the source nodes is multiplied by lsrcdf.

Larger values will increase the spacing (element size) near the sources.

Only applicable if the LSRatio improvement flag is on (mlsr=1).

default=1.4 min=0.5 max=1000

**lsrlimit**

LSRatio improvement limit factor.

Source nodes are generated to improve the minimum length scale ratio (LSRatio), minimum node spacing over distance between boundaries.

If the minimum LSRatio is less than lsrlimit then source nodes will be generated.

A value of lsrlimit=0 will turn off LSRatio improvement.

Only applicable if the LSRatio improvement flag is on (mlsr=1).

default=0.0001 min=0 max=1

**mtr**

Spacing transformation flag.

If mtr = 0 then do not use a local transformation.

If mtr = 1 then use a local transformation with transformation vectors.

If mtr = 2 then use a local transformation with transformation vectors along with geometric growth defined by parameters cdfrsrc and cdfssrc. Typically not applicable with meval>=1.

The transformation vectors may be set from sources (if msource>=1) or an externally defined sizing function (meval>=1).

AFLR2/AFLR3 parameter.

default=0 min=0 max=2

**mdflim**

Distribution function limiting flag.

If mdflim = 0 then do not limit the distribution function.

If mdflim = 1 then limit the distribution function by the minimum local boundary edge length multiplied by the satisfied edge length multiplier, cdff.

This option is intended to limit the distribution function for cases with high-aspect-ratio faces on boundary surfaces.

default=1 min=0 max=1

**meval**

External evaluation option flag.

If meval = -2 then use interpolation from sources for sizing evaluation. This option is set internally if sources are input and meval=0.

If meval = -1 then use interpolation from an input background grid for sizing evaluation. This option is set internally if a background grid is input and meval=0.

If meval = 0 then do not use external sizing evaluation routines.

If meval >= 1 then use externally defined sizing evaluation routine to determine the distribution function, metric and transformation vectors for new nodes. If a site dependent specific routine is coded, compiled and linked with the executable then this option is useful. An external routines may or may not use a background grid (if any) and/or source nodes (if any) that are input to AFLR. AFLR includes a built-in external sizing evaluation routine. By default the built-in external routine is useful only for testing. The built-in external routine provides 4 different test cases selected by setting meval=1,2,3,4.

default=0 min=-1 max=100

**mdf**

Distribution function flag.

If mdf = 1 then interpolate the node distribution function for new nodes from the containing element.

If mdf = 2 then use geometric growth from the boundaries to determine the distribution function for new nodes.

default=1 min=1 max=2

**cdf**

Distribution function multiplier.

The distribution function is used to specify desired element size. The distribution function originally determined from the average of the surrounding boundary edge lengths is multiplied by cdf.

Increasing cdf will increase the total number of grid nodes generated. Decreasing cdf will decrease the total number of grid nodes generated.

Deviation of cdf far from a value of 1.0 will degrade the element quality next to the boundaries. A cdf value above 1.0 will create elements adjacent to boundaries that are elongated normal to the boundary.

In the rest of the field the elements should be relatively isotropic.

default=1.2 min=0.5 max=3

**cdfr**

Maximum geometric growth rate.

Used as the advancing-front growth limit. The element size for new nodes is limited to be less than the physical size of the local front advanced from multiplied by cdfr.

Also used as the geometric growth rate for the node distribution function with the growth option (mdf=2). A cdfr value just above 1.0 will produce a grid with optimal element quality.

A value of cdfr well above a value of 1.0 will decrease the number of grid nodes generated and potentially decrease the element quality.

default=1.1 min=1 max=3

**cdfs**

Distribution function exclusion zone.

Distribution function growth exclusion zone factor used with growth option (mdf=2).

The node distribution function and element size remains constant near a boundary node for a distance equal to the node distribution function at the boundary multiplied by cdfs.

default=1 min=0 max=10

**cdfn**

Nearby node factor.

Nodes are considered too close if the distance between them is less than their average node distribution functions multiplied by cdfn.

default=0.7 min=0.5 max=0.9

**cdfnbcf**

Frozen boundary face nearby node factor.

Nodes are considered too close to a frozen boundary face node if the distance between them is less than their average node distribution functions multiplied by cdfnbcf.

default=2 min=0.5 max=100

**cdfqrg**

Initial re-generation distribution function multiplier

The initial re-generation distribution function multiplier cdfqrg is used to specify the relative element size during quality improvement grid re-generation.

Only applicable if the quality improvement re-generation flag is on (mqrgen=1).

default=1 min=0.5 max=1e+06

**cdfqrgmin**

Minimum re-generation distribution function multiplier.

The minimum re-generation distribution function multiplier cdfqrgmin is used to limit the minimum distribution function multiplier during quality improvement grid re-generation.

Only applicable if the quality improvement re-generation flag is on (mqrgen=1).

default=0.5 min=1e-06 max=1e+06