Early CFD Simulation Means Better ROI

Many engineering organizations have moved computational fluid dynamic analysis to the beginning of the design cycle. Other companies find they can now afford CFD software, as it’s increasingly becoming integrated with the CAD packages they already use.

These companies want engineers themselves to find and fix the design issues that contribute to problems with air or fluid flow rather than waiting until the design is completed, then sending it to a CFD analyst within the company. By making early design analysis the purview of engineers rather than specialized analysts, these organizations slash the design cycle, lower their engineering costs, and find a better return on investment. Engineers design, analyze to find potential design flaws, then redesign, meaning they iterate quickly to get to the optimal model. The specialized analysts who step in later on the project are met with parts that don’t need nearly the tweaks as they would without earlier engineer-led simulations. The designs meet specifications without being over-designed.

The capability to take time out from an ongoing design to run a CFD simulations and analyses—and then correct for flaws immediately—speeds the design cycle. And it contributes to the democratization of CFD analysis. That is, it allows for more people within the organization to carry out analysis and allows for more—and smaller—companies to purchase and use CFD software.

To do this, CFD capabilities are being integrated with the CAD design software engineers use everyday. Those tied systems allow engineers to move quickly and seamlessly between model construction, model analysis, and redesign.

For example, FloEFD from Mentor Graphics has been recently integrated with the Solid Edge CAD system from Siemens PLM. FloEFD is also embedded in other popular CAD programs such as Creo, from PTC; and NX, also from Siemens PLM.

A Buick production line at the Shanghai General Motors’ factory. Image is from China Daily.

To take a look at how CFD can be used earlier in the design cycle, look to engineers at the Pan Asia Technical Automotive Center in Shanghai. The center engineers Shanghai General Motors vehicles as well as acting as one of six global GM technical development and design centers.

With the huge increase in car ownership in China, drivers now seek the same vehicle comforts those in the West enjoy, including air-conditioning that maintains a uniform temperature throughout the passenger cabin.

Engineers at the center used FloEFD to examine a range of hedge angles for hot and cold airflow channels and determine how best to design the air conditioning unit, according to Lu Ping, an engineer at there.

Ensuring that uniform temperature is a matter of engineering and airflow. The position of the doors act as a control valve inside the air conditioning unit and ultimately determines the hot and cold airflow “mixing ratio” The “hedge angle” and “area ratio” of the cold and hot airflow channel have an important influence on the final mixed airflow temperature distribution.

“The software showed ways to improve design performance to achieve an optimized design and at the same time reduced our overall cost of development,” Ping said.

Engineers found a hedge angle of 120 degrees and an area ratio of 39 percent respectively to be optimal for maintaining uniform cabin temperature, he said. They subsequently engineered the unit to reflect that angle and allow for that area ratio.

“We adopted FloEFD for this study because of its ease of use in meshing when compared to the tetrahedral or prismatic meshing approaches in traditional CFD codes,” Ping said. “Since it works within the mechanical CAD environment, it’s a highly engineered universal fluid flow and heat transfer analysis software.”





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