The Molecular Flow Module is a tool enabling the design and simulation of low pressure gas flow in vacuum systems. Kinetic effects become important as the mean free path of the gas molecules becomes comparable to the length scale of the flow. Under these conditions, conventional fluid dynamics tools cannot produce an accurate model. Flow regimes are categorized quantitatively via the Knudsen number (Kn) that represents the ratio of the molecular mean free path to the flow geometry size for gases:
| Flow Type | Knudsen Number |
|---|---|
| Continuum flow | Kn < 0.01 |
| Slip flow | 0.01 < Kn < 0.1 |
| Transitional flow | 0.1 < Kn < 10 |
| Free molecular flow | Kn > 10 |
While the Microfluidics Module is used to model slip and continuum flows, the Molecular Flow Module is designed for accurately simulating flows in the free molecular flow and transitional flow regimes.
The Molecular Flow Module uses a fast angular coefficient method to simulate steady-state free molecular flows. Isothermal and non-isothermal molecular flows can be modeled and the heat flux contribution from the gas molecules is automatically calculated. The discrete velocity method is also included for the simulation of transitional flows.
The Molecular Flow Module is ideal for the simulation of vacuum systems including those used in semiconductor processing, particle accelerators and mass spectrometers. Small channel applications (e.g. shale gas exploration and flow in nanoporous materials) can also be addressed.
A number of improvements have been made to the Molecular Flow interface. Processes such as chamber pump-down and film growth can be designed and optimized through simulation by utilizing the features for defining adsorption / desorption and deposition. The interface has been modified to allow meshing of the surfaces of the geometry only, greatly simplifying the mesh generation for complex CAD geometries. Finally functionality to recover the number density anywhere within the flow geometry has been implemented.
| Note: To use any of the COMSOL Modules, a COMSOL Multiphysics Base License pass is required. All module software is included with the COMSOL Multiphysics download file, which means you need to download only once. |
- Access is authorized within the geographic boundaries of Canada only.
- Use of this design tool is restricted to university research only.
- Faculty with a Professor Research Subscription receive access that allows you, your students, and your research staff to access COMSOL software.
- Five concurrent use instances per tool from the subscriber’s research team, up to the limits of the available licenses in the shared pool
- Access for one year
- Acceptance of the vendor licenses terms www.comsol.com/sla, including the Academic Addendum, on first use.
For more information, contact the Licensing Administrator at licensing@cmc.ca or call 613-530-4787.
