Nearest Neighbor Distance

Nearest Neighbor Distance statistics record time-evolving statistics describing the distribution of neighbors within a particle set. As discussed on the Nearest Neighbor Distribution theory page, the shape and properties of this distribution provide insight into the degree of particle dispersion and blending throughout the vessel. These outputs include both ensemble-reduced statistics and full ensemble distribution data. The data is printed when Compute Nearest Neighbor Distribution is enabled for any particle set. For additional information on how to use these files, see the associated tutorial video.

Each particle set with Compute Nearest Neighbor Distribution enabled produces a tab-separated ASCII .txt file named NearestNeighborDistance_{DynamicName}.txt, where the dynamic name corresponds to the name of the Particle family in the model tree. This file contains ensemble-reduced statistics including the expected and realized ensemble-average nearest-neighbor distance, as well as a measure of the goodness of fit to the expected nearest-neighbor cumulative distribution function (CDF).

In addition to the ensemble-reduced statistics, the code outputs the time evolution of the expected and realized nearest-neighbor probability density functions (PDFs) and cumulative distribution functions (CDFs). These files are written to a directory named ./NearestNeighborDistance_{DynamicName}. Files within this directory are named according to the output time.

Both the ensemble-reduced statistics and the distribution data are written at the Statistics Output Write Interval.

Jump to: NearestNeighborDistance_{DynamicName}.txt | NearestNeighborDistance_{DynamicName} Directory

NearestNeighborDistance_{DynamicName}.txt

The NearestNeighborDistance_{DynamicName}.txt file contains ensemble-reduced nearest neighbor statistics that evolve with simulation time. Each row corresponds to a statistics output time, and each column reports a specific statistic associated with the nearest-neighbor particle distance distribution.

The index table below describes the statistics written to this file. Each statistic corresponds to a column in the output table that evolves with the Time column. The units listed are the engineering output units.

Statistics	Units	Details	When Appears
Average Nearest Neighbor Distance	m	mean nearest neighbor distance
Expected Average Nearest Neighbor Distance	m	expected mean nearest neighbor distance, based on total fluid volume and number of particles using complete spatial randomness Poisson process
Fit to Expected CDF	Dimensionless	measure of fitness between actual and expected nearest distance cumulative distribution fuction

NearestNeighborDistance_{DynamicName} Directory

The ./NearestNeighborDistance_{DynamicName} directory contains files that store the time-evolving nearest-neighbor distance distributions. Within this directory, a separate file is written for each statistics output time, using the format time_{PrintTime}.txt, where PrintTime is the physical simulation time. Each file corresponds to a specific output time and contains the probability density function (PDF) and cumulative distribution function (CDF) evaluated over the nearest-neighbor distance domain.

Within these files, each row corresponds to a distance location in the nearest-neighbor distance domain. The table below describes the values written to each distribution file. The PDF and CDF represent the realized particle distribution as well as the expected distribution based on complete spatial randomness.

Distance values are reported in meters. The PDF and CDF values are dimensionless.

Statistics	Units	Details	When Appears
CDF	Dimensionless	value of cumulative distribution function at given distance
Distance for CDF	m	distance for cumulative distribution function
Distance for PDF	m	distance for probability distribution function
Expected CDF	Dimensionless	expected value of cumulative distribution function at given distance, based on total fluid volume and number of particles using complete spatial randomness Poisson process
Expected PDF	Dimensionless	expected value of probability distribution function at given distance, based on total fluid volume and number of particles using complete spatial randomness Poisson process
PDF	Dimensionless	value of probability distribution function at given distance