What is in:Flux?

in:Flux is CFD software that analyses ventilations and gas dispersions within complex geometries. It is aimed at all engineers, including those who have never previously performed a CFD themselves. The speed and simplicity of in:Flux is unrivaled, so that organizations such as yours can now carry out CFD modeling at a fraction of the time and cost associated with other CFD products.



Why is in:Flux Useful?

Many of the tasks that require a high level of CFD expertise are handled automatically by in:Flux. For example, meshing is entirely automatic – the mesh will refine around geometry and regions of high gradients. Numerical discretization schemes and physical models are all automatically set, as are boundary conditions and convergence criteria. The user is simply required to input the required wind speeds and directions, and point sources of gas emissions and wait for the solution to complete. This level of automation provides assurance of high quality CFD results.


Once the simulation has finished, the user can add streamlines, contour plots and 3D isosurfaces to analyze the data. All the post-processing can be output to images files for reporting.



What Makes in:Flux Different?

  • It is the only CFD software specifically designed for dispersion and ventilation analyses, eliminating the need of expertise to 'tweak' general purpose codes.

  • It can interface directly with many CAD formats (DGN, DWG, DXF, IGES, STEP, OBJ, STL), no approximations are made to the CAD geometry.

  • All meshing, boundary conditions, and numerical setup is automated.

  • Post-processing visuals can be added after calculations have finished rather than hope planes defined prior to the simulation contain relevant information.

  • Once the process is understood, multiple simulations can be set up very quickly. As an example, a knowledgeable user of in:Flux can set up 100 CFD cases in less than 20 minutes.

  • Simulations are automatically scheduled, and do not require any interaction or scripting after setup.

  • The user interface allows access to all CFD simulations at once, rather than one at a time. This means that post-processing of all simulations can be done without the need for building complex in-house scripts.




The in:Flux documentation is always being updated. We strive to develop these tutorials and guides to go over all the major features of the software. Throughout 2020 and beyond Insight Numerics will be pushing updates as our validation cases are finalized.


As some of the more advanced features have not yet been covered in the guide, please feel free to email us inquiries as we continue to release updates.



Building blocks of an in:Flux project

The steps below list the procedure of carrying out a dispersion simulation using in:Flux. The steps should be carried out chronologically as each step is based on the previous, the exception being post-processing which can be viewed after ventilation simulations have complete.


  1. CAD - import a 3D CAD file or create one from the CAD Creation Tool

  2. Ventilation - A wind simulation MUST be defined before a dispersion analysis can take place. This is because a mesh needs to be established as a foundation for the dispersion simulation to be accurate.

  3. Inflow (gas leak) - an inflow is a general term that represents any source of dispersed gas, for most cases this will be a gas leak

  4. Dispersion - once all of the prior steps have been added to the project, a dispersion simulation can be run by combining a single ventilation with a single inflow within an imported CAD file.

  5. Post-Processing - after a simulation has completed (ventilation or dispersion) visuals can be added to the project to better understand the results. Monitor points and regions can also be defined at any time during the project to obtain specific values of variables in the simulation.



Steady-State Simulations

in:Flux simulations are automatically set to be steady-state. This means that there is no concept of time – all in:Flux is trying to simulate is the established gas plume.


In reality of course, there will always be a finite inventory, so upstream pressures will drop, flow rates will decrease, until eventually nothing comes out of a gas leak. If this happens very quickly, then steady-state simulations such as these are not appropriate – you have to use a transient CFD simulation. However, it is quite rare that you really need to go to a full transient, because “quickly” usually means “quick relative to the plume establishing a steady state”. If you look at actual gas leaks, the plume establishes very fast in the near-field (e.g. lengths associated with offshore leaks). Clearly if you are interested in the very far-field, then the plume establishment takes longer.


So you only need full transient simulations when the decay of the release rate is fast relative to the time it takes for the plume establishment. As mentioned, this is not normally the case.



Transient Simulations

As of version 1.1, in:Flux allows users to run transient simulations - giving the ability to view flow characteristics at a specified time. When adding a dispersion to the project, simply change the 'Scheme' under the Transient section. Additionally, a shutdown (ESD) time and inventory volume may be added to high pressure gas leaks via the add items tab.



Future Developments

Keep watch for updates regarding the release of new features to in:Flux including multi-phase leaks, escape analysis and more.





As we continue to improve in:Flux making it more accurate to match experimental data, the tutorials may lag behind the most current in:Flux build. Thus, when going through the tutorials you may receive slightly different results on your version than results shown and displayed in this help file. If you have any questions about the results you are receiving, feel free to contact us at info@insightnumerics.com and we will be happy to help you.