1.5 m Trisonic Blowdown Wind Tunnel

Half-model of Bombardier Global Express business jet

This major facility is a pressurized, intermittent flow wind tunnel capable of running in the subsonic, transonic and supersonic flow regimes. The speed range is from 1/10 to more than four times sonic speed.

Stream stagnation pressure is closely controlled during the blow-down and, by varying the diffuser throat area or controlling the outflow from the plenum chamber, the test Mach number may be held within very close limits as a model pitches, even at sonic conditions.

1.5 m test section being inserted in high-speed wind tunnel plenum

Support provided:

• wind tunnel testing techniques
• wind tunnel instrumentation
• model design, model manufacture
• data analysis capability
• computational fluid dynamics.

Testing configurations
The basic test section is 1.5 m square with solid walls for measurements in subsonic and supersonic flow. For high subsonic and transonic flow regimes, a separate test section with perforated walls is contained within a pressure-tight plenum chamber and minimizes the impact of shock reflections and blockage. A test-section insert (0.38 m wide and 1.5 m high) is available to produce aerodynamic data on 2-D aerofoil sections. Chord Reynolds numbers approaching full-scale values on transport aircraft for Mach numbers up to 0.9 can be achieved.

While the run time of this tunnel in its various modes depends on the flow conditions required, a typical time is 20 seconds. A captive trajectory system for advanced store-release studies is under development.

CF-18 on roof-mounted sting during stores release test

Model mountings
Complete three dimensional models are mounted using either a rear sting, or a "plate mount" system which permits correct modeling of the rear fuselage for transport aircraft configurations. By installing a "reflection plane" and five- component sidewall balance, it is possible to test semi-span models of larger scale, for which higher Reynolds numbers can be achieved. Two-dimensional models for aerofoil development are supported between three component balances in each sidewall.

Data acquisition and analysis
In addition to force and moment data, high-precision surface pressure measurements are routinely made on aircraft or aerofoil section models. These measurements are made using electronic pressure scanning (EPS) techniques. Force and moment measurements can also be made on external stores in the parent aircraft flow field.

The data system used for recording nominal steady state information is built around DEC PDP and VAX computers with extensive disk storage. A high-speed data acquisition system (with 192 channel capacity and sampling rates to 40 kHz per channel) is also available for making measurements involving unsteady phenomena.

Pilot wind tunnel
NRC Aerospace also operates a one-twelfth scale "pilot" version of the 1.5 m wind tunnel which offers the same performance envelope, with virtually unlimited running times. This facility is very cost-effective for testing small models, such as the calibration of flow measurement probes.

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