Biggest Wind Tunnel In N.Z.

Press, Volume CII, Issue 30312, 12 December 1963, Page 15

Biggest Wind Tunnel In N.Z.

The biggest wind tunnel in New Zealand is now taking shape at the University of Canterbury School of Engineering. Looping back on itself overhead, it is 57ft long, nearly 18ft high, and more than 10ft wide.

A massive fan, with the motor built into its- boss, will produce winds at constant velocities ranging from one or two miles an hour to 140 miles an hour.

This huge construction. occupying almost the whole of one of the mechanical engineering laboratories, is necessary for a working section measuring only three feet by four feet The contraction of seven to one needed to bring the big tunnel of wind into this smaller space will increase the velocity seven times and ensure that the draught is parallel to the working platform. The total enclosure of the circulation system (the fan will recirculate the air within the structure) will avoid any turbulence from outside. This tunnel will be used extensively for aerodynamics and fluid mechanics research, but it is also likely to have many other uses. It is, for instance, the only tunnel in the country capable of testing accurately the wind loading on building structures. The aerodynamic design of the tunnel was started by Mr D. C. Stevenson, senior lecturer in mechanical engineering. eight years ago—well before the engineering school moved to Ilam. Construction began last February, and it will be toward the end of next year before the tunnel is commissioned. Fifteen tons of steel will

go into its erection: many chains of angle iron and scores of 12ft by sft sheets of steel plate. Everything is welded. The method follows aircraft construction with “stressed skin.”

This is a “home-grown” job. Mr Stevenson (with a student, Mr J. Atvars, who is now in Canada) did all the designs, and Mr E. Retallick, senior technician in mechanical engineering, and Mr A. E. Taylor are doing all the construction.

The engineering school already has some magnificent models of aircraft for use in experiments—a Comet, a Canadian CFIOO, a D.H. Swallow and an Avro Delta—some of the world’s latest jets. More prototypes will be added later. All the present models were made to exact scale by the Royal Aircraft Establishment, Farnborough. Under test, models will be securely mounted on a deli-cately-balanced platform which will measure minute lift and drag forces. Electronic devices will record every influence. rhe maximum velocity of 140 miles an hour to be produced in this tunnel is not spectacular but it is the highest which can be used in scale-model work without introducing factors of incom-

pressibility which arise at math numbers.

But nearby work has started on a supersonic tunnel in which wind velocities up to about 2000 miles an hour can be achieved. Air for this will be stored in bottles at pressures of 30001 b a sq in. This will pass through complex pressure-reducing valves and heaters to recover temperature and then through a contraction assembly into the working section only five inches square. Mach 5 is the maximum velocity for this work as, above it, oxygen and nitrogen in the air would liquify

Associated with the wind tunnel work is a new electromagnetic vibrator which can apply, constantly or variably, any loads or stresses likely to be experienced in practice. The British Ministry of Aviation is following this work with interest. Yet another installation, recently completed, is an assembly to study jet noise. The jet nozzle is outside the mechanical engineering laboratory and steam is being used through it for fundamental research.

All these projects have been under the direction of Mr Stevenson, who will leave next week to take up an appointment as senior lecturer in fluid mechanics at Monash University, Melbourne. Mr Stevenson had started work in all these fields as a civil servant in England when he came to Christchurch in 1954. In 1959 he spent a year at the Royal Aircraft Establishment, Farborough, studying the effects of jet noise on structural fatigue and also noise levels at airports. In Melbourne he hopes to concentrate on jet-noise research.