In wind tunnels, the interaction of the objects with air can be observed. All the aero vehicles and the vehicles or structures having interaction with the air, are effected from the aerodynamic forces and moments. The determination of these forces, moments, flow configuration and physique are very significant for the designers.
In wind tunnels, the aerodynamic properties of the aero vehicles like airplane, helicopter, parachute, balloon etc., and the land carriers like automobiles, trucks, buses, and the interaction of the buildings, towers, bridges with the air can
Ankara Wind Tunnel (AWT), which was established between 1946-1950 and repaired by TÜBİTAKSAGE between 1993-1998, is a closed circuit, horizontal loop, low speed wind tunnel with a closed atmospheric test section. Test section size is 3.05 m X 2.44 m X 6.10 m in width, height and length, respectively. In the test room the flow velocity can reach up to 90 m/s (324 km/h). The full sized object or the scaled model is assembled to the test section. The flow velocity can be supplied up to 324 km/h. The tested object can be positioned to required angle and with the help
of internal and external balance systems the load measurement or the flow observation can be carried out with diverse techniques.
- Load Measurement Test
- Load measurement tests are carried out when the determination of aerodynamic loads is required.
External and internal balances are used to obtain the aerodynamic forces with different speeds, model angles or model configurations. Both type of balances are used for the determination of aerodynamic forces. While the external balance system is taken place at the outside of the test room, the internal balance system, with different size and load capacity, is taken place in the test room inside the model. Both balances have 6 components. The selection of which balance is going to be used is done after an analysis before the test according to the geometry and the aerodynamic properties of the material that is going to be tested.
• External balance system
• Internal balance system (2 units).
The balance systems can operate between -10 and +45 °C. For each balance system, the load capacity and the working principle are different.
All balance systems have the ability of measuring three aerodynamic forces and three aerodynamic moment coefficients. The force and the moment values depend on the scale of the model and the completion of the model.
Required engineering support is given by AWT staff before the tests.
Generally aluminum, steel, composite or wooden materials are used as wind tunnel model materials. Selection should be done in such a way that, it should withstand to the aerodynamic and gravitational forces, and it should have minimum deformation while testing to eliminate the damage to the model or to the tunnel. In the selection of the wind tunnel materials, proper design and verification methods should be used.
- Flow Visualization Test
These tests are carried out when the visualization flow and the determination of the flow properties are required to figure out the aerodynamic incompatibilities. In Ankara Wind Tunnel the flow visualizations tests can be performed with the smoke, oil or tuft methods.
- Equipments and Materials
Smoke generator (DANTEC model), nylon light yarn, tuft board, oil (with different viscosities) and kaolin materials.
Generally aluminum, steel, composite or wooden materials are used as wind tunnel model materials.
Material selection should be done in such a way that it should be withstand to the aerodynamic and gravitational forces, and it should have minimum deformation while testing to eliminate the damage to the model or to the tunnel. In the selection of the materials, proper design and verification methods should be used. When a flow visualization test is going to be done, the model should be painted in black.
1. Test room Dimensions: 3.05 m x 2.44 m x 6.1 m
2. First diffuser and safety screen Diffuser angle: 3-5˚ Length: 8.7 m
3. Turning vanes (first two lines) Airfoil shaped. The leading edges are concrete, the trailing edges are wooden.
4. Propeller and guide vanes 5 m diameter propeller on a shaft with 220 mm diameter. Direct current engine with 1000 BG (750 kW) power and 600 rev/min, 7 guide vanes.
5. Second diffuser Diffuser angle: 8˚Length: 24.5 m
6. Turning vanes (second two lines) Airfoil shaped. The leading edges are concrete, the trailing edges are wooden.
7. Turbulence screens 3 metal items with 1 m interval before the contraction cone
8. Settling chamber and contraction cone Contraction ratio: 7.5