Defining Upfront CFD

By Ed Williams, Blue Ridge Numerics, Inc.

1. Our customers have no interest in making a career of CFD. 2. Solving flow and thermal problems is only a fraction of their responsibility. 3. They are capable engineers with a solid grasp of the fundamentals of fluid and thermal dynamics.  4. The products they design and the product performance issues they face can be very complex. 5. Getting answers/knowledge early in the process is their primary motivation.  6. They are pragmatic users of technology. Simulation must plug into the existing workflow and carry a value proposition that justifies the addition of yet another software application to their already crowded toolbox.

So how does this picture affect the definition of upfront CFD? First and foremost it tells us that traditional CFD cannot be adequately re-configured or reverse engineered to satisfy such users. They are too smart and too busy to invest money and time into tools that were not made specifically to help them achieve their professional goals.

The First Tenet of Upfront CFD

The first tenet of upfront CFD is that all geometry changes must be made in the MCAD system and the CFD tool must automatically and instantaneously recognize and adapt to design changes without loss of product data. This logical approach is very uncommon in the CFD world today because “real” geometry made in the MCAD system is too complicated for traditional CFD meshing tools. In the structural world, this is much less of an issue since the solvers are predominantly based on FEM (finite element method).

FEM has two major advantages over the older finite volume approach used by traditional CFD vendors:

1. Finite elements can accept elements of different shapes and geometries easily and naturally;
2. The theory behind FEM is more mathematically based rather than physics based as in finite volume solutions.

FEM produces the best solution (one that minimizes the residual globally)  on the given mesh and is much more tolerant of high aspect ratios and skewed elements. This delivers great benefit when building geometrically complex models. FEM provides the geometric flexibility and robustness essential to widespread upfront usage.

A commitment to this first tenet also eliminates the need for importing or translating a product design into the analysis environment. These two processes strip the geometry of all intelligence (part IDs, material properties, etc.) assigned in the MCAD environment and disconnect the assembly from essential product data such as the BOM, assembly constraints, toolpaths, and drawings. By using the CAD model to drive CFD simulations and using the CAD system for all geometry changes applications such as CFdesign create value for the user, process, and business.

Nothing Low-End about Upfront CFD

Recently, a breed of CFD applications that is sometimes classified by experts as “dumbed-down” or “low-end” and yet is marketed to mechanical design engineers as design-level and CAD-integrated software has proliferated. These tools offer subsets of flow and thermal simulation capabilities found in traditional CFD packages but fall short of offering a true solution. Stripping out essential simulation capabilities to make the software easier to use simply proves the developer still doesn’t understand the upfront CFD customer.

Solving tough problems that involve laminar, turbulent, and even transient flows is in the mechanical design engineer’s job description. They are routinely confronted with complex heat transfer challenges that include radiation, natural and forced convention, joule heating, and the like. They need more analytical power, not less.

Packaging full-spectrum analysis capabilities in an easy-to-learn,  easy-to-use, CAD-integrated environment is far from low-end technology. Simplicity is the ultimate sophistication.

It is our view that the adoption of upfront CFD is not reliant on any major mathematical or scientific breakthroughs. The defining ingredient is intimate knowledge of the customer.

Ed Williams is president of Blue Ridge Numerics,  makers of CFdesign upfront CFD software. Send Ed your comments via e-mail c/o DE‘s Editors.