Traversing systems

Critical to the success of many wind tunnel test programs is the ability to capture information about the acoustic and aerodynamic flow fields surrounding the model under test. NRC has developed a number of traversing systems which provide efficient and accurate measurements of these important flow parameters.

All traversing systems operate under closed-loop servo controlled systems enabling rapid and accurate positioning of measuring instruments and probes. Many traverse systems are multi-axis. Results are processed and displayed via graphical software interfaces immediately following the run so that clients can access this important information in a timely fashion, allowing critical decisions to be made without undue delay.

In the 9 m wind tunnel a six-meter long array of five-hole probes is mounted on a single axis traverse capable of six meters of travel. This system allows a 6 m x 6 m cross-flow plane to be surveyed in about 20 minutes, yielding quantitative information about three orthogonal flow velocity components. The entire traverse system can be re-positioned in a stream-wise direction to study the development of wakes and vortices. The 9 m wind tunnel also possesses a 2 m high wake rake with the same instrumentation, capable of finer resolution of the flow field.

A two-axis traversing system is available in the open circuit propulsion and icing wind tunnel. This system is again capable of surveys in planes normal to the free stream direction, and can be re-positioned in a stream-wise direction.

In the 2 m x 3 m wind tunnel there are several traversing systems. A roof-mounted system with four degrees of freedom is capable of conducting surveys in polar coordinates behind yawed propellers for example. A second roof-mounted traversing system is designed to survey wakes behind scale-model surface vehicles mounted on the groundboard.

In the trisonic blowdown wind tunnel a single axis vertical traverse is often used behind models in the 2D insert. This system has been optimized to work effectively in the demanding conditions that transonic testing creates. The system is used to provide momentum deficit measurements to estimate drag, and to determine shedding frequencies behind bluff bodies.