3 Finger-Thumping Myths of CFD and the Realities Associated with it
Posted by: Mehul Patel | Posted on: March 19th, 2013
Computational Fluid Dynamics (CFD) simulation has long had a reputation of being too difficult, slow and expensive to be performed in the main stream design process. That may be true a decade ago but things have drastically changed recently. Yet there are certain myths associated with CFD in the early phases of mechanical design. These myths help explain why only about 30,000 out of over 1 million mechanical design engineers worldwide use CFD to simulate fluid flow inside and around their products. Let us straight away discuss these myths and realities associated with them:
Myth #1: CFD is too Difficult to be Used in Design Process
Reality: In a recent survey of mechanical engineers, it was found that 58% of engineers do not have the requisite experience and exposure to use a CFD tool. This was absolutely true a decade ago but now things have changed drastically. Now engineers have deep knowledge of CFD to obtain accurate results.
Previous generations of CFD software were also quite sophisticated in a sense that there was lot of tuning and tweaking required to manually modify cells to improve mesh quality and adjust solver controls such as relaxation factors in an effect to get it to convergence to a solution. These reasons specifically threw light on the fact that there was a need for a specialist who could use CFD software and perform it as a part of the design process.
But in the last few years a new generation of CFD software has been introduced that addresses all the relative weaknesses that were displayed earlier in the software. Now with the help of 3D CAD data, automatic grinding of flow space, and managing the flow parameters as object-based features eliminates the need for engineers to understand the computational part of CFD and thus it helps them to focus on the fluid dynamics of the product and gain mastery in it.
The new CFD software has sophisticated automatic control systems that ensure convergence in almost every application without the need for manual tuning. Perhaps the most important function controls the quality of the mesh to avoid one of the biggest reasons for run divergence. Virtually the only situation where the software will not converge is in a problem with a naturally unsteady flow. This type of problem can usually be solved simply by switching to transient analysis.
The necessary skills required to operate the CFD software include the requisite knowledge of CAD system and physics of the product. The engineer is able to focus their time and attention on optimizing the performance of the product as opposed to operating the software which was the case earlier.
Myth #2: CFD takes too Long to Use During the Design Process
Reality: CFD has always been used as a validation step after the design process is over. In the past the major reason for CFD to take too long was because of the fact that meshing process took a very long time. More so, if design iteration were to be analyzed during the design process, it would have been superseded by other iterations before the analysis results were available. This used to require a time-consuming manual step of translating the geometry from the CAD software to the CFD package. From this point, another tedious step was required to extract the cavities from the CAD model and then mesh them. The new generation of CFD software greatly reduces the time required for analysis by automating all of these steps. In the new approach, native 3D CAD data is directly used for fluid flow simulations without the need for translations or copies. Now all the ancillary data required for flow simulations is directly linked to the CAD model and carried along with all design changes. The software analyzes the CAD model and automatically identifies fluid and solid regions without user interaction. Then the automatic masher creates the mesh while maintaining the skewness and aspect ratio thereby eliminating the need for manual intervention. The results are there to be seen as the new parts and design changes can be meshed in a matter of minutes.
Myth #3: Most Products Don’t Need CFD analysis
Reality: In the past CFD was limited to number of industries such as automobile, aerospace, and power generation that led to a belief that CFD adds value to only high-value products. But fluid flow has a major impact on the performance of wide range of products. Every product which interacts with fluid or gas and every production process involving fluids or gases is a potential subject of analysis. That is the major reason why CFD is now used to improve diverse products such as swimming pools, toilets, lawn sprinklers, gas meters, production, printing system, disk drives, and oil filters.
About Author: Mehul Patel specializes in handling CFD projects for Automobile, Aerospace, Oil and Gas and building HVAC sectors. He works as a CFD consultant with Hi-Tech CFD for the past 5 years and has successfully executed numerous CFD projects of high complexities. He is an expert in turbo-machinery, gas dynamics, Combustion, Fluid Dynamics, multiphase flow analysis, computational fluid dynamics etc.