### 6.4.3. Demonstration Experiments

The purpose of a demonstration exercise is to build confidence in the ability of a CFD method to simulate complex flows. While validation studies have shown for a number of building block experiments that the physical models can cover the basic aspects of the target application, the demonstration cases test the ability of a method to predict combined effects, including geometrical complexity.

#### 6.4.3.1. Description

For an aerodynamic study, a typical hierarchy would be:

- Verification - Flat plate

- Validation - Airfoil or wing

- Demonstration - Complete aircraft.

Similar hierarchies can be established for other industrial areas.

#### 6.4.3.2. Requirements

Typically, the detail of the experimental data is much lower than for verification or validation cases.

Completeness of information to set up the test case is of similar importance as for validation cases and involves the same aspects as listed below:

- Geometry

- Boundary conditions

- Initial conditions (for unsteady flows)

- Physical effects involved.

Typically, the level of completeness of the data for demonstration cases is much lower than for validation cases. It is therefore even more essential to identify the missing information and to carry out sensitivity studies with respect to these data.

In terms of postprocessing, demonstration cases often do not provide a high degree of detail. They are usually not appropriate to identify specific weaknesses in the physical models or the CFD codes. Typically, only the point data or global parameters, as efficiencies, are provided.

Even though the density of data is usually lower, the quality should satisfy the same criteria as for validation cases. Error estimates are desirable and so are independent measurements.

Due to the limited amount of data available, the information is usually not sufficient to carry out consistency checks.

The requirements in terms of availability/openness are usually lower than for validation cases, as the demonstration applies usually to a smaller audience. A demonstration case might be carried out for a single customer or one specific industrial sector. It has to be ensured, as in all cases, that the data can be shown to the target audience of the simulation.

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