DEFINITION:

Wind tunnels are essentially used in R&D to study flow phenomena and to simulate on scaled models the aerodynamics of any aircraft or other aerodynamically relevant object. Geometry, Mach number and Reynolds number are, in that order the main similarity conditions for a precise (nearly exact) simulation. Other conditions may apply (e.g. inertia, real gas…).

Depending on what needs to be simulated, numerous (>100) techniques have been developed, some common to most tunnels, some more specific to a certain class of facilities.

(Source: ACARE Domain 108)

SUBDOMAINS:

1. Model design/manufacturing: concurrent engineering, from CFD to CAD/CAM, quick prototyping systems.
2. On-line data acquisition/reduction systems: high sampling rates for unsteady flows, handling of large data bases, standardised data presentation.
3. Wind tunnel flow conditioning: flow quality survey/improvement (angularity, turbulence, noise), high Reynolds number simulation (pressure, cryogenics), high enthalpy tunnels.
4. Full or semi-span model common techniques: global & local loads, pressures, boundary layer transition checking, aerodynamic coefficients, buffeting boundaries, visualisations, model support and wall interference correction/reduction.
5. Airframe/propulsion integration: air intakes, nozzles/afterbodies, motorised nacelles, propellers, helicopter rotors, stealth.
6. Flow/surface flow survey: by intrusive and/or non intrusive means.
7. Specific techniques such as : Aeroacoustics, Aeroelasticity/flutter, Jettison (free drop & captive trajectory), Ground effect, Dynamic derivatives, Heat transfer (hypersonic).