Little-known but useful software tools for modeling reactive flows – FlameMaster and DARS
In this post I would like to discuss two software tools which, while not as popular as Fluent, STAR-CD or CHEMKIN, can come very handy for some applications. For researchers on a budget, which probably means all of you reading this, these tools are either free, or are much cheaper than their competition. Since there is no such thing as free lunch – there are some downsides to keep in mind, which I’ll review as well. The tools that I would like to discuss here are FlameMaster and DARS, respectively.
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Now back to our discussion.
Let’s start with FlameMaster. This is a 0D/1D code for modeling combustion phenomena and flame speed calculations. It was developed by Prof. Heinz Pitsch from Stanford University. I had the pleasure of meeting Prof. Pitsch several times during my career as well as using FlameMaster to produce results for my Ph.D. thesis.
Who could use this code: Anyone studying combustion in the areas of power generation, propulsion, or automotive research.
Why someone would use it: Once installed and compiled, FlameMaster is a reliable and relatively easy code to use. It has been under development by Prof. Pitsch for over ten years. If you need to find out how chemical reactions are influencing your system, do not have money to spend on a commercial package and have some programming expertise, FlameMaster might be the tool for you.
I used FlameMaster to test detailed chemical mechanisms for hydrocarbon fuels and compare the results to those obtained with reduced chemical mechanisms. I was also able to conduct sensitivity analysis and species analysis and use those results to create reduced mechanisms. If you need to obtain autoignition times, laminar flame speeds or calculate diffusion flame strain-rates, and you do not want to shell out cash for a commercial package like CHEMKIN, this tool might be a great solution.
This code has been updated since I used it years ago while writing my thesis. It has been re-written in C language, so you no longer need a Fortran compiler, the solver has been updated and new documentation has been added to make the user experience easier.
Pros: It is a well tested and reliable code from a very reputable university that is FREE to users. When I spoke with Prof. Pitsch a few months ago, he told me that he also provides consulting services with emphasis on turbulence and chemistry modeling. This might be a great solution to companies who would like some guidance in setting up their simulations. FlameMaster can be used to generate flamelet libraries for CFD software and since it is open-source, you can program it to be coupled with other software codes, such as KIVA, for example.
Cons: Since this is a free code, no commercial grade technical support or training courses are available. You need to have decent knowledge of programming and running code from a command line. There is no graphical user interface. You will need a C compiler if you make any changes to the code. The uses of FlameMaster are limited. It can be great for very specific applications (like generating flamelet libraries or obtaining laminar flame speeds) but it does not allow for modeling of surface chemistry for example or for creating reactor networks. The code has its own format for chemical mechanisms (as opposed to the more common chemkin format)
How you can get your hands on it: visit the FlameMaster website and click on “Request Access” link.
The next piece of software that became available about 2 years ago that I would like to introduce here is called DARS. This tool is distributed by DigAnaRS, LLC. Professor Fabian Mauss from Lund University developed this software to handle a variety of chemically reactive flow applications. DARS is a commercial software package available for purchase and designed to handle both gas-phase and surface chemical-kinetics (non equilibrium conditions).
Thanks to DigAnaRS, I was able to test out DARS on my PC for a number of problems and was impressed with its user-friendliness. DARS has a graphical user interface which allows for the various reactor and chemistry mechanism modules to be drag-and-dropped into a workspace on your computer screen.
There are several versions of DARS, depending on whether you need to run it as stand-alone software or couple its chemistry solver with other CFD or CAE software. DARS Basic is the stand-alone version that provides a number of 0D and 1D reactor models. One of the most exciting features of DARS has got to be its ability to automatically reduce chemical mechanisms based on the sensitivity, flow, and lifetime analysis. This feature can be very valuable to CFD users who need to have good reduced mechanisms to use in their CFD simulations.
DARS Library Generation Tool (LGT) creates flamelet libraries for CFD codes and DARS software manuals claim it to be fast and robust. Ignition libraries for various inlet conditions can also be created using LGT. DARS LGT enables you to model combinations of turbulence interactions with complex, detailed chemistry for turbulent reacting flows.
Finally, DARS CFD provides a chemistry solver as a CFD plug-in. A great example of this is CD-adapco’s STAR-CCM+ software that includes DARS solvers.
Who could use this code: Anyone studying combustion in the areas of power generation, propulsion, automotive research, materials or microelectronics.
Why someone would use it: This is a much cheaper alternative to the CHEMKIN software. As a new customer you can get personalized attention and help that would typically be lacking when purchasing software at larger companies.
This is the first commercially available, publicly distributed software that claims to automatically reduce chemical mechanisms. Of course there are plenty of open-source codes that have been developed for mechanism reduction (more on those in future posts), based on methods such as Computational Singular Perturbation. However, this is the first, commercially supported software tool that claims to have this capability. If you are aware of other software that does this, please let us all know in the comments at the bottom of the post.
If you are looking to better understand the chemical processes in your CFD simulations, or need software that would help you to take a closer look at what’s happening in your system at the chemistry level, this might be just the tool for you.
Pros: User-friendly, no compiling required (except in a few specialized cases), includes a graphical user interface. Automatic mechanism reduction allows you to create custom reduced mechanisms on the spot. Reduced chemistry is VERY touchy and reduced mechanisms are typically only valid in very narrow range of input parameters. DARS allows you to create reduced chemistry suitable for conditions that you define as input variables.
Since you would be purchasing DARS, you should be able to get access to technical support, manuals, examples and training. Make sure to ask a DigAnaRS representative what type of support you would be getting if you decide to buy this tool.
There are a number of engine models available as well, including HCCI and Spark Ignition models. DARS has the ability to couple with automotive 1D codes such as GT-Power, allowing you to accurately simulate chemistry while using those 1D codes.
Cons: This is a new tool. Although the software is very promising, there are a lot of bumps and kinks that still have to be worked out. Do not expect to be able to read a few manuals and have your simulation running in DARS within a week. DO expect to work closely with the software developers when setting-up your system. Expect to find bugs and report them to the developers.
If you need an out-of-the box solution, you have some flexibility in your budget, or you need reactor network capability (currently not in DARS) you might want to take a look at CHEMKIN-PRO as a more established option.
How you can get your hands on it: visit the DARS website and click on “Contact and Support” icon.
I want to give you the information that really interests you as engineers, researchers and educators. Have a suggestion for a software review or an interview with a researcher in this field? Please write it up in a comment!
Looking forward to hearing from you, as always.
Tags: CD-adapco, chemical kinetics, chemistry mecanisms, chemkin, computer modeling, computer simulation, computer software, DARS, engineering modeling, FlameMaster, reactive flow, reactive flows