by Derrek Cooper

I read a blog post yesterday attempting to explain Upfront CFD and then comparing it to traditional CFD and concurrent CFD. Yea, Concurrent CFD was a new one for me too. A fancy word for “CAD embedded” CFD. It’s been around for a number of years and when you first look at it, sounds great!! A CFD tool that lives and breathes right in my CAD tool. Awesome! Immediately, there is a comfort level that everything will be ok and it can get the job done. For very simple (geometric and physics related) problems, where comparing one design to the other isn’t important, this can be true. But even for the simple problems, it can come up a little short. Let’s take a look.

The Problem

MCAD tools have been around for awhile, they were built from the ground up to design 3D parts, generate 2D prints and the like. They can be fairly intensive programs with tons of features. Many companies have laid an FEA program on top of this foundation and have been fairly successful. SolidWorks Simulation is super popular for structural simulation. It does a great job for design level simulation. Structural simulation is fairly straight forward these days. Users tend to plot deformation and von mises (others as well) stresses to determine if something passed or failed. Often, you can get away with a simple static image to compare across designs.

In CFD, we tend to look at “pressure drop”, “peak velocity”, “max temperature” etc. We use these values as our pass/fail criteria. But this static data isn’t enough to tell you why one design passed over the other. A static image often just doesn’t cut it. This is where Concurrent CFD begins to break down. The CFD system is laid on top of the heavyweight CAD system, so having the ability and flexibility to compare models quickly and easily in 3D becomes impossible. You are now spitting out images and laying them on your desk, really hard to see what’s going on “inside” the model. This is one of the fundamental differences between CFD and structural FEA. The action of structural FEA happens on the outside (surface of the model). With CFD, the magic, often happens on the inside. In other words, having the ability to slice/dice and COMPARE in 3D is essential.

Often, users find that the honeymoon of CFD living inside their CAD system lasts for a very short time. Many of the CAD embedded programs are developed by 3rd parties which requires them to add functionality on top of the CAD framework. The result is that you have 20+ brand new dialog boxes that are popping up on the screen. So are you really in a familiar environment anymore? I’d argue that all of the familiarity and comfort of flying around in your CAD tool goes out the window. You are often locked down by wizards and forced to follow a specific recipe. This works fantastic day 1 of training, but many of us want to take off the training wheels and do it our way.

The Solution

Upfront CFD isn’t a new term to learn. It’s been around for 18 years. It has been developed from day 1 to address one simple purpose – to empower design engineers to solve fluid flow and thermal design challenges early and throughout the entire design process. Upfront CFD has all of the comforts of your CAD system- mouse operations are the same, layout is native and clean (works exactly the way you expect), CAD materials and attributes are read directly from the native CAD system as well as being fully associative. But the gem of Upfront CFD is the ability to properly do what-if scenarios.

The real impact of Upfront CFD is the ability to conduct multi-scenario design studies in a single environment. The environment is completely associative, you can clone designs or scenarios and update any change made to the CAD model. These clones are extremely lightweight, not simply entire copies of the previous, and give you the flexibility and power to do numerous what-if scenarios. Automation is one of the fundamental concepts of Upfront CFD. The data can be reused intelligently from one scenario to the next with a simple click of a button as well as being reused for future simulations.

multi-scenario design study environment

Once you have your defined results, whether they are critical values such as max temperature or pressure drop or 3D results, you can compare the data side by side instantly. Imagine having 4 designs that you want to see the flow behavior or temperature profile in 3D side by side? Click of a button in Upfront CFD, impossible in Concurrent or Traditional CFD. That’s the difference!

The Disclaimer

Many of you know this, but fair to state that I’m the Product Manager for CFdesign, so this may come across as grand standing. Not my intention. I am just trying to lay out some of the facts and dispel the myths. There is a place in the world for traditional CFD- PhD-type research problems, extremely massive models that require compute farms to crank out and when comparison is not important. This is a fairly niche market, but valid nonetheless. Same goes for Concurrent CFD. The market is even a bit more niche as it caters to very simple problems, that are fairly small in size and complexity and comparison is of little value.

Don’t take my word for it- go out there and check it out. Google it all- the facts are there.

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Derrek Cooper is a mechanical engineer who is obsessed with technology. He is product manager for CFdesign upfront CFD software. He blogs as The Virtual Engineer, and tweets at http://twitter.com/derrekcooper.