Molecular Flow Module
Molecular Flow Module
Model Low-Pressure Gas Flow in Vacuum Systems with the Molecular Flow Module
Understanding and Predicting Free Molecular Flows
Vacuum engineers and scientists use the Molecular Flow Module to design vacuum systems and to understand and predict low-pressure gas flows. The use of simulation tools in the design cycle has become more widespread as these tools improve understanding, reduce prototyping costs, and speed up development. Vacuum systems are usually expensive to prototype. Therefore, an increased use of simulation in the design process can result in substantial cost savings. The gas flows that occur inside vacuum systems are described by different physics than conventional fluid flow problems. At low pressures, the mean free path of the gas molecules becomes comparable to the size of the system and gas rarefaction becomes important. Flow regimes are categorized quantitatively via the Knudsen number (Kn), which represents the ratio of the molecular mean free path to the flow geometry size for gases:
|Tipo di flusso||Numero di Knudsen|
|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 for modeling slip and continuum flows, the Molecular Flow Module is designed for accurately simulating flows in the free molecular flow regime. Historically, flows in this regime have been modeled by the direct simulation Monte Carlo (DSMC) method. This computes the trajectories of large numbers of randomized particles through the system, but introduces statistical noise into the modeling process. For low-velocity flows, such as those encountered in vacuum systems, the noise introduced by DSMC renders the simulations unfeasible.
Accurate Modeling of Low-Pressure, Low-Velocity Gas Flows
The Molecular Flow Module is designed to offer previously unavailable simulation capabilities for the accurate modeling of low-pressure gas flows in complex geometries. It 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) may also be addressed. The Molecular Flow Module uses the angular coefficient method to simulate steady-state free molecular flows, allowing the molecular flux, pressure, number density, and heat flux to be computed on surfaces. The number density can be reconstructed on domains, surfaces, edges, and points from the molecular flux on the surrounding surfaces. You can model isothermal and nonisothermal molecular flows and calculate the heat flux contribution from the gas molecules.
Molecular Flow Module
Caratteristiche del Prodotto
- Flussi molecolari liberi
- Flussi isotermi e non isotermi usando il metodo del coefficiente angolare
- Possibilità di discretizzare l'intero dominio di flusso o solo le superfici
- Ricostruzione delle densità di numero per unità di volume di flussi molecolari liberi
- Flussi diffusi, evaporazione, flusso molecolare e condizioni per bacino
- Condizioni al contorno per vuoto totale e pompe per vuoto
- Condizioni al contorno per la temperatura in flussi non isotermi
- Condizioni al contorno di parete per outgassing, adsorption/desorption, e deposizione
- Flussi di transizione
- Flussi isotermi usando l'equazione di Boltzmann BGK impiegando una forma modificata del metodo Discrete Velocity/Lattice Boltzmann
- Condizione di parete solida applicabile attraverso tutto il range di numeri di Knudsen
- Opportune condizioni al contorno per i regimi di Navier Stokes di flusso molecolare per consentire al fluido di entrare o uscire dal dominio di calcolo
Campi di Utilizzo
- Sistemi per vuoto
- Apparecchiature per il trattamento dei semiconduttori
- Apparecchiature per il trattamento dei materiali
- Spettrometri di massa
- Acceleratori di particelle
- Esplorazione di gas da argilla
- Flussi in nanopori
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Molecular Flow Through an RF Coupler
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