G5. Recommendations for Action

The ultimate responsibility for quality assurance lies with the user of the simulation software. It is their responsibility to prevent unsuitable software choices or improper application, as specified in VDI 6201. The software manufacturer must verify their products and the integrated models and validate them based on reference examples. The user is obliged to perform a basic validation of the software concerning the specific application area before independent use.

If the results of a CFD calculation are used for dimensioning purposes, different levels of validation are required depending on the consequence class (CC) of the structure or component, according to the WTG guidelines.

The application of numerical methods (CFD) is subject to the requirements of EN 1990, which mandates the involvement of qualified and experienced professionals. Typically, a minimum of three years of experience in working with the types of structures under investigation and their numerical simulation is expected. A mesh dependency analysis is mandatory, with references allowed to comparable in-house studies.

In practice, RANS/URANS calculations are predominant, providing experienced wind engineers with a quick overview and valuable supplements to literature values. However, with RANS, significant deviations can occur when the calculated mean pressure coefficients are used to estimate peak pressure based on the equivalent gust in standards. While this approach is suggested by the format of wind load standards, it does not align with the original methodology used to determine these values.

Using more complex models such as LES or DES does not automatically ensure "correct" results. Particularly, the accurate formulation of inflow conditions poses a significant challenge and requires special attention and expertise.

Table 8: Possible Requirements for Validation