Six steps for successful FloTHERM studies
By Dirk Niemeier, Customer Application Engineer, Mentor Graphics
FloTHERM is a very powerful tool. The size and complexity of the range of models that can be simulated begins at chip level and ends far beyond the rack level, with varying degrees of complexity: from simple cuboids to sophisticated, detailed models. Hence carefully planning and conducting a FloTHERM study is of utmost importance to the design process.
Step One: Scope out the project
Before you start, you should ask yourself what kind of information you need from the virtual experiment. This will define what needs to be included in your model and how detailed it has to be. Even drawing a sketch on a piece of paper can be helpful.
When building your model, use as many SmartParts as possible. SmartParts are constructed parametrically, making it easier to conduct a parameter controlled optimization.
Step Two: Define your data
Then define what input data you will need, geometry, physical properties and - of course - component power losses. These should be as realistic as possible, using maximum ratings often are not accurate enough. Take your time to gather all the required data. Always remember: the results are only as good as the input data.
Step Three: Build your model
When building your model, use as many SmartParts as possible. SmartParts are constructed parametrically, making it easier to conduct a parameter controlled optimization. Always build the model with reasonable tolerances, i.e. avoid small distances and gaps as this improves the quality of the grid. Make sure materials are attached to all geometry and power losses where required. Once the geometry is set up, choose an appropriate solution domain size. If physical processes outside the domain can be neglected, it may be as big as the geometry, otherwise it needs to include some space around the geometry. Don’t forget to add Monitor Points, they allow an insight into what is going on in the solution while the solver is running. Ideally, Monitor Points should be placed in critical components or in regions of interest.
Step Four: Create your grid
Once the geometry and the solution domain are set up, you can add the computational grid. Start with the presets of the System Grid and refine the settings step by step. In most cases you will need to add grid locally by Grid Constraints and localized grid spaces on objects. Always refine the grid in areas where you expect high gradients or where higher resolutions is required for higher accuracy. While setting up the grid, monitor the grid quality closely. For example using the Grid Summary can help to eliminate cells with large aspect ratios.
Step Five: Run the solver
Once the model and grid setup are complete, the solver can be run. The Profiles window shows both residuals and Monitor Point values during the solving process. Although the FloTHERM solver is very robust, you should keep an eye on both residuals and Monitor Point values. If the solution is converging poorly or Monitor Points show unrealistic values, some model settings may be wrong. Stop the solver and try to fix the problem.
Step Six: Analyze the results
The results of the simulation can be viewed either graphically or in tabular format in the Visual Editor. The options are diverse and I would like to encourage you to play around with the many graphical ways of displaying results. For a beginner, the Tables may be difficult to read but are worth understanding as they can reveal many physical details the graphical results miss, e.g. heatpaths.
The results of simulations very often lead to the question: How can the design be improved?
The Command Center is designed to help to answer this question. Within the Command Center you can run parametric studies as well as optimizations of your basic design. This final step will complete the study.
If you follow this route, your FloTHERM studies will be always successful. However, if you run into trouble, please contact support: We are always here for you!
About the Author
A physics graduate from TU Braunschweig, Germany, holding a Ph.D. in Physical Chemistry. Dirk joined the company in 2002 as an Application Engineer. Since 2008 he has been a Customer Application Engineer for the Mentor Graphics’ Mechanical Analysis Division, supporting and teaching users of FloTHERM, FloVENT and related products.