CFD

by Barb Schmitz, Senior Editor

Products vary in size, shape, complexity, and usage so it’s hard to generalize anything about product design. The processes by which companies create new products, however, are typically the same. First they define what the product will do (product specifications), and then they capture all of the things that will define the product (design intent).

Once that has been agreed upon, the design team creates detailed designs and tests these burgeoning product ideas to see if they actually behave in the real world the way in which they are designed. When or if they don’t, changes are made to the design and they are tested again. This testing was once conducted using physical prototypes, which is both costly and time-consuming to conduct.

Today this process is very different and more efficient, thanks to virtual testing using simulation software. Digital models are now put through their paces in virtual prototyping environments using simulation software, such as finite element analysis (FEA) or computational fluid dynamics (CFD). Often later in the cycle, physical prototyping testing is used to confirm the simulation results so product designs can be moved onto manufacturing.

Simulation speeds up decision-making
Every step of the product development process is littered with questions, most of which can be answered in multiple ways. How big should it be? How strong does it need to be? Can we reduce its weight? If we reduce its weight or use less material, will it affect its strength? Can we use a different material? Answering these questions as accurately and quickly as possible has a direct impact on both the cost and speed of product development.

After all, engineering is all about asking many questions, making mistakes, changing things, and on and on until you arrive at an optimum solution or design. Calculations, prototypes, and analysis are all tools that provide guidance to engineers as the design moves through the design cycle. Most product geometries are too complex for hand calculations and physical prototypes are costly and built too late in the cycle to be used to optimize designs upfront.

Simulation has emerged as the best way to do all of that quickly and at least cost—both in terms of actual cost and time to market. Originally conducted later in the design process, there is abundant evidence that suggests that products should be simulated throughout the design process. In fact, most agree that simulation should start at the very beginning of the design cycle, during concept development, to quickly vet the ideas being considered and put designs on the best path.

How analysis is used in product design
The shift from simulation tools being used for product validation to an essential part of upfront design requires a paradigm shift involving changed processes, new tools and new ways of thinking for engineers.

Engineers are increasingly turning to simulation early in the design cycle, during concept development. At this stage of design, the product geometry is basic so multiple iterations using simulation can be done quickly so product designers can quickly answer ‘what if’ iterations and move forward with the best design alternative.

“With product design, it’s important to get off to a very good start,” said Bernt Nilsson, senior vice president of Marketing at COMSOL. “When you’re implementing simulation, you want to start in the very early stages, or conceptual design phase. At this stage, when you want to get a basic proof of concept going, you want very simple models. That means you’re using very basic geometry, avoiding including too many details that would slow down the analysis.”

Having some level of integration between CAD and analysis enables engineers to test ideas, adjust designs, explore, and verify to confirm that designs are on the right track, minimizing the risk of flawed designs moving forward when changes are most costly. In other words, design-integrated analysis enables design teams to explore more design variants in less time.

Who should be using simulation tools?
The reality is that simulation tools are as a whole being underutilized at most companies. Possibly the problem is more cultural, than technological. Many engineering managers have not mandated or allowed a process change that leverages simulation. In addition, the question as to who should be using these tools continues to be debated.

A recent CIMdata report cites complexity as one of the underlying issues preventing more widespread adoption. To make simulation software easier to use, several vendors developed simulation packages that are directly integrated with CAD systems. By and large, however, these CAD-integrated simulation software were also not widely embraced by the industry.

Many believe this is due to the fact that not many engineers and product designers–for whom these products were developed–understand the underlying fundamentals of simulation. According to the CIMdata report, “democratization is about simplifying the application of the tools and making them more widely available. It is not for these powerful tools to be used by those who do not understand the product and engineering issues.”

Many vendors maintain that only simulation or R&D experts should use simulation tools; that these tools should not be “dumbed down” for engineers to use. Others maintain that simulation will not meet its potential in terms of benefits to the design process until it is widely embraced by design engineers.

Simulation tools are typically offered as standalone software or as CAD-integrated software. With the latter, the simulation tool is launched directly from within the CAD environment, the simulation uses native CAD geometry, and many of the pain-provoking steps of traditional simulation—such as meshing—has been automated. There are benefits to both approaches.

“Fully integrating simulation capabilities within the native design environment of mechanical design engineers provides them easy and direct access to the benefits of up-front simulation throughout their design stages,” said Robin Bornoff, PhD, Market Development Manager, Mentor Graphics Mechanical Analysis Division. “Whether it’s Creo, CATIA V5 or Siemens NX, being able to simulate a design without suffering the pain of data interoperability with standalone simulation tools puts simulation directly under their control.”

Several CAD vendors, such as SolidWorks, contend that simulation tools should be embedded in the CAD software to best enable engineers to leverage their use. “Nowadays, all product engineers can leverage their mechanical engineering knowledge to design better products using 3D CAD and simulation tools,” said Delphine Genouvrier, Senior Product Portfolio Manager, SolidWorks Simulation. “With CAD-embedded simulation, every engineer involved in product development can apply corrective action on the design that is triggered by the insights provided by the simulation results.”

Other vendors have focused on automating functions within their software that enable engineers and product designers to use simulation tools without having the domain expertise of experts. “CFD simulation has historically required knowledge of the underlying algorithms to be able to select appropriate options for a given application,” said Bornoff. “Automating such choices liberates the design engineer from this pre-requisite, allowing them to focus on their given design challenge and not the numeric of the tool employed.”

Bridging the gap: how engineers and analysts can work together
Some highly complex design scenarios require specialized tools, such as multiphysics simulation software, which typically requires the expertise of R&D and simulation specialists. This, however, doesn’t mean that simulation results are not of use to product designers and engineers. High-end simulation developers have worked hard to create capabilities that facilitate this interaction between the simulation specialists and the product engineers. Providing better ways for these two groups to collaborate enables the design process to be iterative and benefit from insights provided by simulation results.

“You have this interaction between the simulation expert and the design engineers so you need tools that support that collaboration. We’ve invested a lot into making it easier to combine COMSOL with CAD, because it’s crucial to get that right,” said Nilsson. “Our LiveLink products enable you to take a large CAD assembly and combine or link it with your simulation in COMSOL. You have this bidirectional link so when you make a change to the CAD geometry, it is automatically updated in COMSOL.”

When CAD-embedded simulation tools are being deployed, the interaction between the engineers and the specialist looks slightly different. Engineers deploy the simulation tool for optimization of design concepts and analysts use the tool later to do final validation.

“Product engineers can detect early potential product issues, improper behavior and compare their design ideas with ‘what if’ scenarios,” said Genouvrier. “So when the analyst receives the product later in the process, it has already been optimized and tested for product performance so they can then focus on final validation or complex simulations, using their expertise in advanced analysis rather than doing product optimization. This is a win-win situation for the entire company.”

The reality is that at each company, simulation experts are small in number compared to the number of engineers so careful consideration must be made in terms of how to make best use of their time.

“Analyst experts are few and far between in the context of the number of design iterations that are considered during the design process,” said Bornoff. “The question is how best to utilize their competence. ‘Turning the handle’ to simulate each design iteration can and should be done by the designer. When a problem is identified, then that is the time to involve the analyst. Not because they have experience in using an ‘advanced’ simulation package, but because they have the domain expertise to be able to identify and recommend a remedial design solution.”

Design culture must adapt to maximize benefits
In order to truly maximize their investment in analysis tools, companies need to stop propagating the idea that simulation can’t drive design; it can only validate them. Without a process change, designs being validated digitally are the ones that would have been validated through physical prototyping. So where’s the value add?

Better user training is also in order. Users need to better understand what simulation results are telling them, either about the design or about the quality of the simulation. Additional training on input properties, material properties and failure mechanisms will empower them to make better decisions and look further to find the optimal configuration

Whether simulation tools are being used by specialists or by product engineers—or both—simulation holds the key to reduced physical prototyping, higher-quality, more optimized products, and faster design cycles. The key being that design optimization must happen early in the design cycle when changes can still be made without significant rework, lost cycle time or significant expense.

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COMSOL
www.comsol.com

SolidWorks
www.solidworks.com

Mentor Graphics
www.mentor.com