Which wind tunnel test configuration studies the aerodynamic characteristics of a specific mode?

• A. Three-Dimensional Global Model Test
• B. Full-Scale Wind Tunnel Test
• C. Two-Dimensional Local Model Test
• D. Two-Dimensional Test of Rigid Model with Spring Support

Answer: (D)

Isolating a single vibration mode in wind tunnel testing requires a setup that behaves like a simple oscillator for that mode. A two-dimensional rigid model mounted on spring supports creates a defined restoring force for the chosen degree of freedom, giving a specific natural frequency and damping. With the model allowed to respond in that mode, the wind tunnel can reveal the aerodynamic forces and stability characteristics associated with that particular mode, such as pressure distribution and flutter tendencies, without the influence of other modes.

Other configurations study broader or different aspects: a three-dimensional global model test examines the overall aerodynamic behavior of the full structure; a full-scale wind tunnel test tests the actual structure at full size; a two-dimensional local model test looks at sectional aerodynamics without isolating a specific modal response; whereas the spring-supported, rigid two-dimensional setup specifically targets the response of a single mode.