It is therefore essential to categorize the requirements for numerical investigations into appropriate groups, based on the problem and objective definition. This allows different procedures to be derived from varying accuracy requirements (see Table 3).
Table 3: Typical Minimum Requirements for Numerical Methods and Assignment to Investigation Subjects and Example Questions
| Category | Class | Requirement | Explanation |
|---|---|---|---|
| Accuracy Requirements | G1 | Qualitative values, low accuracy | For preliminary studies or conceptual design; reduced effort and detail level |
| G2 | Absolute values, medium accuracy | For parameter or preliminary studies; higher accuracy planned for later investigations | |
| G3 | Absolute values, defined accuracy | Quantitative requirements with statistical validation according to design tasks; results verifiably on the "safe" side. | |
| Spatial Requirements | R1 | Solitary, single wind directions | Analysis without surrounding structures, only key wind directions |
| R2 | Solitary, all relevant wind directions | Fine directional increments, without surrounding structures | |
| R3 | Ensemble with neighboring structures | All relevant wind directions, fine directional increments | |
| R4 | Topography and ensemble | Considers topography and neighboring structures, all relevant wind directions | |
| Temporal Requirements | Z1 | Statistical mean values | For stationary flow processes; fluctuations captured by other measures |
| Z2 | Full time resolution | Enables detailed statistical analysis; fine temporal resolution for vortex resonances and structural parameters. | |
| Z3 |
|
Quantitative requirements with statistical validation according to design tasks; results verifiably on the "safe" side | |
| Structural Requirements | S1 | Static effects | Structural model without mass and damping properties |
| S2 | Quasi-static calculation | Determines relevant natural frequencies and dynamic characteristics | |
| S3 | Dynamic modeling | Full representation of temporal behavior; without significant aerodynamic changes due to structural deformations. | |
| S4 | Aeroelastic modeling | Interaction of structural responses and aeroelastic loads (fluid-structure interaction) |
Depending on the chosen numerical or modeling approaches, calculation results of varying quality and significance can be achieved. Generally, the following distinctions can be made for the suitability of the calculation methods, which can then be selected according to their intended purpose:
Table 4: Group Assignment of Numerical Methods with respect to Investigation Requirements
| Group | Results | Explanation |
|---|---|---|
| 1 | Mean Values | Suitable for parameter studies with low accuracy requirements or when using integral force coefficients. Also applicable for certain wind comfort assessments |
| 2 | Mean Values and Standard Deviations | Applicable for time-dependent response variables such as crosswise oscillations from vortex shedding or structural loads from wind gustiness without inherent turbulence effects. Peak factors are assumed |
| 3 | Time Series | Enables precise determination of characteristic loads and maximum/minimum local effects. Corresponds to wind tunnel tests and requires specific requirements for flow modeling. Necessary for effects with inherent turbulence components |
| 4 | Dynamic Structural Responses | Required for significant fluid-structure interaction (aeroelasticity). Depending on the application, methods from groups 1-3 may also be included, where only one-sided interaction is considered |