Particle Output Data

The M-Star Particles/Bubbles Output panel provides a complete description of particle behavior in your simulation. These output properties include individual particle motion/properties, ensemble statistics, spatial fields constructed from the local particle population, as well as particle exit statistics. These outputs are designed for users to understand how particles move and interact, how well they are dispersed, how they exchange mass with the fluid, how long they stay in the system, and where they exit.

Ensemble Statistics and Reduced Data

M-Star produces reduced statistical outputs that summarize ensemble averaged particle properties over time. Ensemble statistics include things like total particle count, mean particle diameter, total interfacial area, etc. This data is saved as ASCII text files at the statistics output frequency.

Particle-Resolved Data

M-Star tracks every particle individually through space and time. Each particle retains its identity and properties over time, including diameter, shape, composition, and any user-defined particle properties. Particles can report on the fluid properties surrounding each particle, including local fluid velocity and strain rate. These local fluid properties are useful for probing local fluid properties and predicting local transport coefficients. The particle-resolved datasets are printed to a binary .vtp file for visualization and analysis within M-Star Post. Each particle family is written to its own file using the dynamic particle family name. The printing is synchronized with the Plane/Probe Write Interval as well as the Volume Write Interval. This makes the output frame-consistent for visualization and animation in both 2D and 3D renderings.

Particle-Derived Fields

In addition to tracking individual particles, M-Star maps the particle population onto the computational lattice to create Eulerian fields. These are spatial fields defined at every lattice cell, just like the fluid outputs. Typical particle-derived fields include local particle volume fraction, local volumetric mass transfer quantities, and local specific surface areas. This field data is printed directly to the slide and volume VTI files for visualization and analysis alongside other field data within M-Star Post. The field printing is synchronized with the Plane/Probe Write Interval as well as the Volume Write Interval.

Exit Statistics and Residence Time Data

M-Star automatically tracks particles that leave the domain and records exit statistics for residence time analysis. A unique particle exit file is written for each particle family with a filename coupled to the dynamic particle family name. For each particle that exits the system, this file presents an accumulated list of the exiting the Particle ID, time added, exit time and location, and key particle properties. This data is useful for computing particle residence time distributions (RTDs), exit age distributions outlet composition, and pathway behavior

Nearest-Neighbor Distance

M-Star computes nearest-neighbor distance to quantify how well particles are dispersed. This output is enabled using the Compute Nearest Neighbor Distribution option. Each particle is assigned a scalar value equal to the distance to its closest neighboring particle. This is stored directly in the .vtp particle output files and can be visualized as a color on each particle. M-Star also reports ensemble statistics of nearest-neighbor spacing, including the mean nearest neighbor distance, and the distribution of nearest neighbor distances. See additional discussion in Theory: Nearest Neighbor Distribution.

Particle Screens

In addition to tracking particles throughout the full domain, M-Star allows you to define particle screens on Output Planes. A particle screen records the moment when a particle crosses a specified plane and captures its state at that instant. This provides a way to measure particle fluxes and spatial distributions along specific planes in the system. When a particle crosses the screen, its landpoint (the intersection point with the plane) is recorded and written as a new particle dataset. These particle-resolved screen datasets are exported as binary VTP files for visualization and analysis in M-Star Post. The name of each output file is automatically linked to the Axis Direction and Intercept Value used to define the output plane.

In addition to the particle-resolved data, M-Star also converts the screen crossings into field quantities. These field outputs include the local particle land point count and the aerial landpoint number density. These field variables are written as additional data to both the screen output plane and the volume output.