Bookmarks to different parts (detailed in the bullet points below) are in the video description:

There are two links for each video:

• Youtube is convenient but has ads.
• CERN video is ad-free.

Intro

Introduction to Monte Carlo simulations

If you're new to these Monte Carlo tools, this presentation is a good overview of the special physics at very low pressures, how it's related to Monte Carlo simulations, and how Molflow actually works.

• Short explanation of the high vacuum physics
• The Monte Carlo method
• History of Molflow and Synrad
• Typical Molflow workflow

 

Molflow

Interface basics

The interface is your first encounter with Molflow, this video shows the basic controls and also some tips and tricks.

• Loading a simple pipe
• Mouse commands (zoom, pan, rotate)
• Default views and area zoom
• View options, view parameters, light options
• Additional parts of the interface, global settings, white background
• Screenshot tool
• Toggling coordinate axes
• Advanced: 4 split views

Selecting facets (basics)

Highly recommended to watch: shows the different techniques to select facets, then memorize them as groups. Mastering these will save you a lot of time later.

• Creating a 100-sided pipe
• Select by clicking on geometry
• Cycle through overlapping facets
• Select by facet number in list
• Options for selection display in volume view
• Select multiple facets
• Selection box
• Multi-select from facet list
• Add overlapping facets to selection
• Memorizing selections
• Recalling and combining selections
• Smart select tool

Selecting facets and vertices (advanced)

Tips and tricks useful for geometry editing and large geometries where using traditional techniques are cumbersome.

• Select by number (facet id)
• Invert selection
• Select vertices
• Select in circle
• Move selection box/circle anchor
• TAB to switch facet/vertex modes
• Difference between add/remove logic
• Restrict selectable facets by Caps Lock

Create geometry with built-in tools

As opposed to importing a geometry from an external editor, you can now create your geometry from scratch. This tutorial walks you through the steps to assemble a basic vacuum system, consisting of two pumping ports and a variable diameter pipe.

Result geometry: ansys_geometry.zip

• Starting with an empty geometry
• Create a circle and extrude it to a pipe
• Create a larger diameter circle at end of pipe
• Create difference of two circles
• Adding vertical pumping ports
• Rotating a circle (using an axis)
• Rotating a circle (using 2 vertices)
• Move a circle by fixed offset
• Move a circle up to an existing facet
• Mirroring a pipe to a plane
• Fixing a 0-area facet with the Collapse command
• Building T intersections between pipes
• Fixing the T intersection by scaling down vertical pipe
• Clear isolated vertices

A simple vacuum simulation

Finishing the example from the previous video by adding physics and comparing the pressure result with the published paper

Source geometry: ansys_geometry.zip
Solved exercise: ansys_with_physics.zip (with symmetry: symmetric.zip)

• Adding outgassing
• Adding the pumps
• Setting up textures
• Setting up profiles
• Advanced: taking advantage of symmetry

Basic simulation of an RF cavity

An example of a vacuum simulation of a realistic geometry. You can get the source files from this tutorial's page.

• Importing the STL file to Molflow
• Adding outgassing
• Adding pumps
• Starting the simulation
• Adding textures (pressure color maps)
• Playing with mesh resolution
• Manual texture color scaling
• Single counter facet instead of texturing all
• Measuring distances in Molflow
• Setting counter facet parameters and texture
• Visualization techniques
• Adding a profile (pressure along a direction)
• Adding a new profile facet by scaling
• Exporting profiles and textures
• Splitting the geometry horizontally

Conductance calculations

Conductance, part 1: theory and a simple (round pipe) example:

• Theory and formulae for conductance
• Simple round pipe example + analytic solutions
• Constructing the geometry, adding sticking and outgassing
• Using formulas to determine transmission probability
• Monte Carlo vs analytic results
• Calculating conductance from transmission probability

Conductance, part 2: real-life CAD example

• Importing the geometry, collapsing and rotating
• Setting up pumping, desorption and sampling planes
• Creating plugs
• Starting simulation, extracting results
• Using formulas to get average pressure
• Verifying results: changing the pumping speed
• Detailed results after more simulation time

Files:
CAD000567144.stl (Geometry)
test_rf.zip (Solution)

Treating perforated geometries

In the previous video, the perforated wall takes thousands of facets. Luckily, there's a hack to replace it with single facets and achieve a very close result.

• Constructing a replacement cylinder
• Calculating area ratio, hole transmission probability and equivalent opacity
• Replacing perforated wall with cylinder, checking results
• Double-walled version
• Real-life geometries
• Adding a temperature gradient

Files:
period_only.zip (Geometry)
mockup_ready.zip (Mockup and hole simulation)
period_only_solved.zip (Solution)
period_only_solved_doublewalled.zip (Double-walled version)
period_only_solved_comparison.zip (Side by side comparison)

Advanced vacuum diagnostics

Additional tools to get deep insight into the behavior of your system

• Angular profiles
• Direction vector textures
• Velocity profile
• Histograms
• Particle logger

Non-isothermal systems

Vacuum systems with different facet temperatures

• Governing equations
• Accomodation factor
• Thermal creep example

Sequential simulations (intro)

Simulating a vacuum system with a large pressure difference in multiple steps

Sequential simulations (angle maps)

Recording an angular distribution and generating gas with it

Sequential simulations (superstructures)

Gaining ray-tracing speed from sectioning the geometry to smaller parts

Symmetry and similarity

Advanced tools taking advantage of symmetries in the system and similar structures

• Symmetry plane
• Periodic systems and teleports
• Inverse teleports

Time-dependent simulations (basic)

• Acoustic delay line example
• Timewise plotter
• Pressure evolution plotter
• Time-dependent physical parameters

Source geometry: adl1.stl
Solved result: adl_timedep_outg.zip

Time-dependent simulations (advanced)

• Radioactive decay
• Surface sojourn time