New Zealand Engineering 1997 February

Letters To The Editor

Letters To The Editor Can Be Sent To:
Letters, Nz Engineering, Freepost 3938, Po Box 12-241, Wellington Or Emailed To Peter@Ipenz.Org.Nz

Membership status

The current issue (November 1996) carries a letter from MR Furness on the IMAGE of an engineer. I agree with his sentiments and feel it is time for the Institution to take an active lead in this regard.

My letter in February (1996) suggested the authors of articles and letters should be identified as members or otherwise of this Institution (or other professional body). Subsequently, C Oxley wrote in support. Geoff Henderson in September made the point that "This does not mean that the word engineer is dead for our purposes. It is up to us revitalise it by usage, education and example."

Much to my surprise, the brochure for the Wellington conference makes little reference to membership status or qualifications, there would appear to be only nine members involved in presenting papers.

I look forward to fuller information in the Proceedings.

Richard Atkins
Wanganui

Computer simulation

I refer to the article 'Computer Simulation of Fluid Dynamics' by Don Campbell published in the November issue of New Zealand Engineering.

The writer's definition on Turbulence, in my opinion, did not cover satisfactory engineering or scientific interpretation. I propose the following explanation:

Turbulence fluid motion is an irregular condition of flow in which the various quantities show a random variation with time and space coordinates, so that statistically distinct average values can be discovered.

Time and space coordinates are necessary, for it is not sufficient to define turbulent motion as irregular in time alone.

Taylor and Von Karman have stated in their definition, turbulence can be generated by friction forces at fixed walls or by the flow of layers of fluids with different velocities past over one another.

In case of real viscous fluids, viscosity effects will result in the conversion of kinetic energy of flow into heat, thus turbulent flow, like all flow of such fluids, is dissipative in nature. If there is no continuous external source of energy for the continuous generation of the turbulent motion, the motion will decay. Other effects of viscosity are to make the turbulence more homogeneous and to make it less dependent on direction.

Dr MA Zaher
Auckland

Wellington's Wind Turbine

The choice of the windmill in Brooklyn, Wellington, as an image for IPENZ promotional material (the latest brochure and the '97 conference material) seems inappropriate. That windmill is a piece of Danish, not New Zealand, engineering.

(We didn't put it there - Ed)

Geoff Henderson
Wind Torque Limited