As FEA is slowly becoming a mainstream design and engineering tool, perhaps Computational Fluid Dynamics is set to be the next big thing for mainstream integration.
by Martyn Day, editor, CADserver, January 30, 2003
Charlottesville-based Blue Ridge Numerics has been intent on providing a core set of Computational Fluid Dynamics analysis tools that could be used by the designer and engineer, rather than the dedicated analyst. And to do so, it has developed a system which works alongside your workhorse CAD system, be it Inventor, Pro/Engineer, Solid Edge, Unigraphics or SolidWorks.
It’s been around a year since I last looked at their product, but at the time, that fifth major release of CFdesign saw the interaction between your workhorse 3D CAD system and Fluid Flow and Thermal analysis take a great leap, with advanced integration with the leading CAD systems and its CFD functionality. So what have they got up their sleeve for Version 6?
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If you’re seen CFdesign before, or indeed, are currently using it, the first thing you will notice is that the user interface has been dramatically changed. Whereas in previous releases, the CFD workflow was split into separate section and separate applications, everything is now conducted in a single application window. Existing users may be a little worried about readapting their knowledge to this new way of working, but the interface has been designed so that it’s not only easier to use and all of your information is available to you, but that the CFD workflow is logically followed.
The majority of the screen is taken up with a model viewing and manipulation window, as ever powered by OpenGL (dependent on the graphics hardware present in your machine). AS you might also expect, there are the usual array of pull-down menus at the top of the screen, but in all honesty, its use is going to be minimal as the majority of functions and interactions are found in the two ‘panes’ to the left-hand side.
The higher of these two is a hierarchical tree-style browser, which almost every CAD user will be familiar with. But rather than providing access to the modeling history and feature tree, this provides you with quick access to all of the parameter and variables present within the CFD analysis case. Below this is another simple window, whose function is controlled by the tabs up the right-hand side. Descending in order, these tabs are based around the discreet processes that you must go through to fully define your CFD analysis study. Each section contains only the options applicable to that particular stage, so it’s clear what stage you’re at, and what’s left to do.
CFD is a very computationally demanding process and it’s not uncommon for routine jobs to take half a day or more. So, while CFdesign (and in all honesty, other similar applications) allow you to set-up multiple design iterations easily, the calculation of those multiple jobs is going to be a bit of a nightmare. In reality, if you want to carry out such beneficial investigation of many product iterations, then you’re going to need some serious hardware.
One option may be to build the mother of all workstations and dedicate it to that purpose, but still, you’re limited to two processors, which means only two cases could be solved at a time. The other option is to buy a supercomputer, from the likes of SGI or HP, but that’s going to cost – a lot.
The other option is to use something often referred to as Cluster or Grid-based computing. This is similar to the render farm concept, whereby standard networked workstations are used to extend the number of processors available to carry out calculation of individual frames of animations, then sent back to the ‘controlling’ or client machine. Blue Ridge’s Fast Track technology is similar in many ways, except that the output is CFD results, rather than nice shiny images.
Unlike many render farm systems, set-up is minimal and control is very simple indeed. Assuming that you’re carrying out your work on your client workstation, you then have access to a list of other workstations on the network running the solver software. You can then create a number of iterations of a single product or indeed, entirely different jobs and assign each a particular workstation (down from a single drop down list). If any of the machines have multiple processors, you also have the advantage that each processor can be running an analysis each. Once each machine has finished, the results are then sent back to the client server for inspection.
Visualization & communication
Of course, it’s all very well bring able to run many more analyses than would traditionally be possible, but you also need to be able to inspect and compare that increased mass of data – in an effective manner. This is where another new piece of functionality comes into play, with the Design Review Center.
This allows you to connect a number of load cases in a single project, then visualize the different results sets very easily. In short, you simply select the appropriate 3D view, create the various cutting planes and visualization style you want to use, then flip through each iteration, either manually or using simple flick book style animation. Of course, you also have the option to rotate the model, alter view styles and cutting planes etc, and add annotations to each individual ‘frame’ or results set. Although it sounds rather simplistic, it’s very powerful, particularly if you’re working on different iterations of a current or future product, as you can instantly see the effect that design changes have on fluid flow or thermal properties.
Then, of course, you’re likely to want to communicate that data to your colleagues, partners or clients. You have a couple of options. Firstly, you can use the built in reporting tools, which will generate the basics on which you can base your report. You can also save out animations etc. But there’s another new piece of technology which will make the process a lot easier and reduce the confusion when dealing with, shall we say ‘less technical’ colleagues.
The Design Communication Center is a rather clever piece of technology which allow you to output very compact 3D models of your results sets, including the geometry as well as all of the CFD specific results visualization methods. As these files are dynamic, the user can rotate, pan and zoom the models and provide feedback should needs be.
Structural FEA interoperability
Perhaps the most overriding goal for any organization adopting any analysis or simulation tool is to gain a more accurate understanding of how their future products function before committing to manufacture. And despite its power, CFdesign only provides a specific part of that for many products. If you’re at the stage were you’re using CFD in any form, then the chances are that you’re also using some form of structural FEA system. There is a distinct link between the fluid flow and thermal analyses and the structural performance of any product.
From this release onwards, CFdesign will provide greater support for those looking to leverage the knowledge gained from the CFD side of things in their structural analysis. This support is provided by the ability to exchange data between CFdesign and the major analysis systems (including Abaqus, ANSYS, Pro/MECHANICA and Nastran), by means of Input Decks. This means that your structural analysis can be based on much more accurate data (in terms of pressures, thermally-induced stress etc) than would be possible using such systems on their own.
There is an argument that for any form of analysis to become fully mainstream, then the tools need to be available in the same interface as the geometric modeling and manipulation tools. While I think that for many users, this thinking does ring very true, there are many occasions where it wouldn’t be all that suitable. For example, one such glaringly obvious case is when the models under investigation are built in another CAD system than the one your analysis tools are integrated into – as all the benefits that comes from that integration are lost (such as data associativity and parametric relationships). There is also the argument that for such analysis tools to provide the most functionality possible, they do need their own dedicated environment – and that’s always going to be one which differs from the creation of geometry. What perhaps is a more sophisticated idea is to take the ease of use ethic and interaction methods that have seen 3D modeling adopted at such phenomenal rates and to apply them to analysis and simulation.
This also seems to have been the thinking at Blue Ridge Numerics, as this release of CFdesign has been rewritten from the ground up to provide the very specific functions and capabilities of CFD within a working environment with which most 3D CAD users will be immediately comfortable and perhaps more importantly, familiar. The adoption of the tree-style browser is an excellent move forward, if not particularly unique idea and the staggered, process-based approach to the definition of CFD analysis cases makes the whole process much simpler – thankfully without any perceivable ‘dumbing down’ or removal of functionality.