Some say that CFD means “Colors For Directors”, a joke that translates the “visual appeal” that is sold sometimes, but that does not necessarily represent the physical or computational fidelity of the results delivered.
In fact, CFD accuracy is not offered by the software being used, let alone the level of numerical convergence, but by the team of engineers responsible for the calculations. Errors of a CFD software user are directly linked to his knowledge, carefulness and experience. For a specific user, deviations can only be minimized by a deep interaction with others. In the case of inexperienced users, it is important to interact with a CFD specialist on a daily basis to avoid major quality problems.
CFD is not wizardry. To get correct results, it is necessary to understand in advance the types of phenomena likely to occur in order to choose the physical models that best represent them, as well as the most appropriate computational methods. So, before hiring the next CFD service, call your current analysis providers and check if they can tell you how they are performing the simulations, specially regarding:
- the continuity solver (pressure-based or density-based);
- the solution sequence (coupled or segregated);
- the turbulence stress-strain relationship (linear or non-linear) and
- the boundary layer modeling (low-Reynolds or high-Reynolds, as well as the y+ resolution).
While CFD analysts should not be misled neither by the software capabilities or by its market share, service buyers must also be vigilant, because a visually appealing CFD presentation is not necessarily synonym of results of quality.
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