regionSizeDistribution
Description
The regionSizeDistribution function object
creates a droplet size distribution via interrogating a continuous phase
fraction field.
Looks up a phase-fraction (alpha) field and splits the mesh into regions based on where the field is below the threshold value. These regions ("droplets") can now be analysed.
Regions:
- print the regions connected to a user-defined set of patches.
(in spray calculation these form the liquid core)
- print the regions with too large volume. These are the 'background'
regions.
- (debug) write regions as a
volScalarField - (debug) print for all regions the sum of volume and alpha*volume
Output (volume scalar) fields include:
- alpha_liquidCore : alpha with outside liquid core set to 0
- alpha_background : alpha with outside background set to 0.
Histogram:
- determine histogram of diameter (given
minDiameter,maxDiameter,nBins) - write graph of number of droplets per bin
- write graph of sum, average and deviation of droplet volume per bin
- write graph of sum, average and deviation of user-defined fields. For
`volVectorField`s these are those of the 3 components and the magnitude.
- (optional) write graph of histogram of centroids on iso planes
downstream of the injector determined by `origin`, `direction` and
`maxDiameter` up to `maxDownstream`
Operands
| Operand | Type | Location |
|---|---|---|
| input | - | - |
| output file | - | $FOAM_CASE/postProcessing/<FO>/<time>/<files> |
| output field | - | - |
Usage
Example of the regionSizeDistribution function object
by using functions sub-dictionary in system/controlDict file:
regionSizeDistribution1
{
// Mandatory entries (unmodifiable)
type regionSizeDistribution;
libs (fieldFunctionObjects);
// Mandatory entries (runtime modifiable)
field alpha;
patches (inlet);
fields (p U);
threshold 0.4;
maxDiameter 5e-5;
nBins 100;
setFormat gnuplot;
// Optional entries (runtime modifiable)
minDiameter 0.0;
coordinateSystem
{
origin (0 0 0);
rotation
{
type axes;
e3 (0 0 1);
e1 (1 0 0);
}
}
// Optional downstream iso-plane bins
isoPlanes true;
// Mandatory entries if isoPlanes=true (runtime modifiable)
// Plane normal and point definition
origin (1e-4 0 5e-4);
direction (1 0 1);
// Maximum diameter of the cylinder formed by the origin point
// and direction
maxD 3e-4;
// Maximum downstream distance
maxDownstream 6e-4;
// Number of iso-plane bins
nDownstreamBins 20;
// Optional (inherited) entries
writePrecision 8;
writeToFile true;
useUserTime true;
region region0;
enabled true;
log true;
timeStart 0;
timeEnd 1000;
executeControl timeStep;
executeInterval 1;
writeControl timeStep;
writeInterval 1;
}
where the entries mean:
| Property | Description | Type | Required | Default |
|---|---|---|---|---|
| type | Type name: regionSizeDistribution | word | yes | - |
| libs | Library name: fieldFunctionObjects | word | yes | - |
| field | Phase field to interrogate | word | yes | - |
| patches | Patches wherefrom the liquid core is identified | wordList | yes | - |
| fields | Fields to sample | wordList | yes | - |
| threshold | Phase fraction applied to delimit regions | scalar | yes | - |
| maxDiameter | Maximum droplet diameter | scalar | yes | - |
| minDiameter | Minimum droplet diameter | scalar | no | 0.0 |
| nBins | Number of bins for histogram | label | yes | - |
| setFormat | Output format | word | yes | - |
| isoPlanes | Flag for isoPlanes | bool | no | false |
| origin | Origin of the plane when isoPlanes is used | vector | yes | - |
| direction | Direction of the plane when isoPlanes is used | vector | yes | - |
| maxD | Maximum diameter of the sampling cylinder when isoPlanes is used | vector | yes | - |
| nDownstreamBins | Number of bins when isoPlanes is used | label | yes | - |
| maxDownstream | Maximum distance from origin when isoPlanes is used | scalar | yes | - |
The inherited entries are elaborated in:
Usage by the postProcess utility is not available.
Further information
Tutorial:
Source code:
API:
History: Introduced in version v1606+