Commonwealth games fish make a big splash

The Melbourne 2006 Commonwealth games were widely regarded as being a huge success. Perhaps the biggest splash in popularity being the free 'fish show' every night along the Yarra River.

Undoubtedly Melbourne's most popular attraction outside the sporting venues with visitors and Melburnians alike are 'the fish'. Spectators along the riverbanks have marvelled at the intricate metalwork and realistically stylised designs. Many more have been amazed and delighted by the spectacular sound and light show that takes place every night of the Games, between 8pm and 11pm on the hour.

With a budget of $7million for the opening ceremony alone, the entire project was overseen by Creative Producer Keith Tucker from Megafun. The entire Yarra Spectacle received wide critical acclaim, with Melbourne and International media praising the use of the Yarra River and City as part of the ceremony.

The Melbourne 2006 An important ingredient to the overall show was the water fountains. "The fish glow and shimmer in a dance of coloured lights and fountains, dynamic images drawn in the water spray, and a light show coordinated to music".

With so much water being thrown into the air, an important consideration was water drift on to the thousands of spectators lining the river banks. Keith Tucker from Megafun contacted Synergetics to model the spray drift under various wind conditions. The height of the water jets could be reduced as the wind speed increased.

David Featherston of Synergetics was responsible for the Computational Fluid Dynamic(CFD) modelling of this interesting problem. Droplet size and wind speed were the primary governing parameters. Thermodynamic and heat transfer relations were used to determine the minimum droplet size that would not evaporate before reaching the Yarra River bank. Turbulent CFD simulations using Discrete Particle Modelling (DPM) enabled a function to be derived for the maximum water fountain height with respect to wind speed. This was used to control the river displays, preventing spray drift affecting spectators.

Principal Meteorologist Barry Cook provided weather analysis of Melbourne March weather to define ambient conditions. With just 0.4mm of rain being recorded early on the first morning of the competition, the typical Melbourne autumn weather helped to show off the city at its best. The balmy weather also resulted in most evenings being calm enough for the water jets to run at their spectacular maximum extent. Dry weather with infrequent high winds and mild temperatures is the most likely meteorological outcome at this time of year in Melbourne; high odds of outdoor sporting or cultural events not being adversely affected by dramatic weather.

Feed-back from Keith Tucker to Synergetics was, "Your work was a key part of making the fountains happen, and the model seemed to accurately reflect what happened in reality".

This was a pleasing result for the 'Modelling Plus' attitude taken to consulting work at Synergetics. 'Modeling Plus' involves using standard modelling tools plus that extra component to provide practical solutions to difficult environmental and occupational hygiene problems.

Synergetics on the Cover of Clean Air

In mid 2005, Synergetic was contacted by Clean Air Society of Australia and New Zealand (CASANZ), who were in the process of selection an image for the cover for the August 2005 issue of the Clean Air and Environmental Quality Journal. CASANZ had heard about the high quality and cutting-edge design and evaluation work carried out by Synergetics utilising Computational Fluid Dynamics (CFD). They expressed great interest and asked for an industry relevant sample image. Synergetics where more then happy to provide a sample of work previously undertaken.

Large roof vent fugitive emissions, typical of many industries, present difficulties for the prediction of near field building wake dispersion using standard Gaussian dispersion models. The emerging modelling technique of CFD, can provide accurate and detailed building wake resolution and visualisation.

The image shows a heated emission plume from a building roof vent with an oblique incident wind. The emission plume is shown using three different visualisation methods. The ribbon pathlines allow individual emissions to be tracked, giving a time history of the air velocity and emission concentration, shown by the ribbon twist and colour contouring respectively.

A shaded plume allows visualisation of three dimensional iso-contours of emission concentration, which give detailed plume shape and dispersion characteristics. Finally, a traditional ground plane surface contour shows the ground level emission concentration within the building wake.

The visualisation reveals that the plume from the leading edge of the building spirals down the leeward wake and is released at the most downwind corner of the building. Some emissions can be seen to re-enter through open ground level vents. These phenomena are also evident in the downwash wake behind urban and industrial structures and some terrain features such as escarpments.