BUILDING MODELLING | JEWEL CHANGI AIRPORT some modelling of the impact of a waterfall on the internal conditions, which, although crude, was broadly right, says Davey. [In Jewel] the scale of the waterfall and its central location in the space was so integral to occupant comfort that we had to go way beyond making simple assumptions. Designed by WET, the waterfall or rain vortex as it is termed is an impressive piece of engineering. Rain falling on the inner slope of the toroidal roof flows down to a slot opening forming the perimeter of the oculus. From this opening, a vortex of water plunges down eight storeys, the final three of which are contained within a giant, transparent, acrylic tube as it passes through basement retail. At the foot of the fall, water is collected and pumped back up to the roof, to ensure a constant flow of 4.5m3 per minute. The spectacle is enhanced for 20 minutes in every hour, when pumps ramp up to deliver water at up to 23m3 per minute. The intent was to model, in detail, the impact of the waterfall on the space. While the cascading water will naturally cool the air through adiabatic evaporation, its impact on the huge volume was, Davey says, relatively minor. Of much more concern was the air movement generated by the huge volume of falling water. When it came to modelling this, the engineer found very little information. Davey says the modellers spoke to an academic who had modelled airflow in a shower to find out The toroidal roof of the Jewel makes an impressive addition to Singapore why the shower curtain is drawn into the cubical when the shower is in use. That was the nearest approximation we could find to modelling air movement around a waterfall, he says. The design team corresponded with him to outline its proposed methodology, which he endorsed as appearing to be on the right track. The reason it was so difficult to model the impact of the waterfall on the surrounding air is because it is a series of interacting elements. As each drop of water falls through the air it creates a comets tail of drag behind it that accelerates the surrounding air. Then the team modelled what happens when two water droplets next to each other fall through the air: There is some drag, but there is also interference, so it is not a perfect teardrop, Davey explains. The more droplets modelled, the more complex the model. For example, they wanted to know what the impact would be of a droplet PROUDLY LAUNCHING OUR PREMIUM MVHR UNITS HRXE-HERA & HRXE-AURA: DESIGNED TO IMPROVE INDOOR AIR QUALITY Key features Improving indoor air quality by continuously extracting moisture-laden air from wet rooms within the property whilst simultaneously drawing in fresh, filtered supply air from outside Listed on SAP PCDB With low SFP of only 0.50 (W/l/s) for K+1 Suitable for studios up to larger developments Quick and effortless installation and commissioning Included in the Domus Ventilation Continuing Professional Development (CPD) course Supporting your projects Free of charge in-house MVHR and MEV technical drawing services email vent.projects@domusventilation.co.uk for details National network of stockists, close to your sites to guarantee quick delivery! YOUR VENTILATION SPECIALIST 03443 715 523 www.domusventilation.co.uk domusventilation_ 28 March 2021 www.cibsejournal.com CIBSE March 21 pp26-30 Jewel Changi.indd 28 19/02/2021 17:43