CTSP (Contamination Transport Simulation Program)

Overview

CTSP (Contamination Transport Simulation Program) is a PIC-C developed computer code for simulating molecular and particulate contamination transport. The need to model contamination is commonly encountered in vacuum and aerospace industries. CTSP is capable of simulating transport of both molecular (volatile condensable materials) and particulate (micrometer-sized dust grains) contaminants around extremely detailed surface geometries. The code uses a particle-based approach to simulate the transport of material from sources to its eventual settling location in order to estimate the end of life cleanliness levels. This kinetic approach allows CTSP to take into account aerodynamic, gravitational, or electrostatic forces, and to also include inter-molecular interactions in rarefied gas regime. The code implements many contamination-specific material sources, including a detailed model for molecular outgassing and particulate generation. Molecular surface adhesion and desorption physics is governed by surface temperature and material activation energy.

Download

A demo version can be downloaded from the new CTSP website.

Features

Support for many common surface mesh formats including Nastran, Universal, OBJ, STL, and TSS
Restart capability and input file scripting make it possible to simulate contamination evolution using time varying geometry
Detailed model for molecular outgassing based on surface desorption and adsorption from the gas phase
Surface adhesion based on material activation energy and time-dependent surface temperature
Particulate generation per IEST-STD-1246D, ISO-14644-1, or tapelift data
Drifting Maxwellian and effusion sources to model venting of internal cavities
Support for external gravitational, aerodynamic, and electrostatic forces
All particles traced concurrently, allowing visualization of contaminant plume density, mean velocity, or pressure
Transition region can be modeled using Direct Simulation Monte Carlo (DSMC) method
Simulation results exported in VTK (ASCII or binary) or Tecplot format
Available results include time-dependent surface contaminant concentration, histograms of surface particulate population, particle traces, particle scatter plots, and volume data.

Hardware requirements scale with the simulation detail, and large cases can be run on clusters over MPI. The code is currently distributed for Microsoft® Windows®, Ubuntu, and CentOS, but support for additional platforms is possible, as needed.

Licensing

“Annual perpetual” licenses are available to US customers. This license allows the user to continue using the code indefinitely but provides only one year of free code upgrades. Contact us for a quote or a free trial version of the software.

Contamination Transport Analysis Services

In addition, we offer a complete contamination analysis service. This generally involves working with a client to obtain a CAD or an FEM model of the geometry of interest along with a description of contamination sources and the ambient environment. We then prepare the input files, run the analysis using our workstation, and deliver a report outlining the evolution of surface contamination, along with the simulation input files.

Examples

Below are examples demonstrating the code’s ability to resolve detailed geometries, and to model transport of molecular and particulate contaminants. Input files for these examples are included in the distribution package.

Figure 1. Molecular contaminant plume and surface deposition on a generic satellite. The last image shows normalized standard deviation computed
from a 48-CPU run, indicating level of confidence. Thanks to John Chowner from Pointwise for tracking down the CAD file and generating the mesh.

Figure 2. Simulation of a gaseous purge being used to prevent infiltration of particulates onto a detector. The detector
percent area coverage (PAC) scales inversely with purge gas flow rate.

Figure 3. Free-molecular flow simulation from a vacuum chamber retrofit study (Spektor, R., et. al.,
Space Propulsion Conference, 2018).

vacuum chamber water flash off simulation frame 1 — Figure 4. Time evolution of surface water flash off in a vacuum chamber with warm (left image in each plot) and cold (right image) thermal shroud.
Cold shroud leads to a lower chamber pressure.

vacuum chamber water flash off simulation frame 4 — Figure 4. Time evolution of surface water flash off in a vacuum chamber with warm (left image in each plot) and cold (right image) thermal shroud.
Cold shroud leads to a lower chamber pressure.

GUI

While an actual GUI is being developed, you can use our browser-based GUI to generate and edit CTSP input files. The GUI runs locally on your machine – no data is sent to our server.

User’s Guide

CTSP User’s Guide: CTSP-UG.pdf

Revision History:

1.5: Addition of mat-mat interactions, time-varying material properties, splitting of input into multiple files, addition of input file variables, loops, deposition integration, partial pressure based desorption model, additional fixes to TSS loader, SINDA temperature loader, octree optimization, initial work on a view factor based integrator
1.1: Rewrite of the storage octree container to use Morton-Z curve, fixes to the TSS loader.
1.0: Complete code base rewrite to follow modern C++ paradigms, automatic time step sub-cycling, tapelift source, surface histograms, reduced memory footprint for flow data.

References

L. Brieda, “Numerical Model for Molecular and Particulate Contamination Transport”, AIAA J. Spacecraft & Rockets, Vol. 56, No. 2, 2019 (link, pdf)
L. Brieda, “Molecular Contamination Modeling with CTSP”, Proceedings of 30th International Symposium on Rarefied Gas Dynamics, Vol. 1786, No. 01, 2016, http://doi.org/10.1063/1.4967536 (pdf)
L. Brieda, “Molecular Outgassing and Deposition in EP Applications”, 34th International Electric Propulsion Conference (IEPC), Kobe, Japan, 2015 (pdf)