Modeling to predict snow drifting in the world’s harshest winter climate
As plans were being made to replace the Halley V Research Station on Antarctica’s Brunt Ice Shelf, the British Antarctic Survey (BAS) engaged RWDI to assess three competing designs for the proposed Halley VI Research Station. We are widely acknowledged as experts in the assessment of snow drifting, with our expertise in this area dating back to the genesis of the company in 1972. Since then we have worked on a number of stations in Antarctica as well as numerous buildings and industrial structures in the Arctic Circle.
A research station has been occupied continuously at Halley since 1957, and in 1985 it was there that scientists first observed the hole in the ozone layer. After the first four British research stations each succumbed to snow accumulation, Halley V was built with the ability to raise itself above the accumulating snow. It was completed in 1992, but its stilt legs still were fixed in the flowing ice shelf. Its location was compromised in the early 2000s when crack growth showed that section of the ice shelf would soon find itself adrift.
In 2004, BAS and the Royal Institute of British Architects (RIBA) organized an international competition to select a designer for a new station. Although the new structure, Halley VI, was to be designed to be relocatable to avoid becoming close to the ice shelf or being cut off by a crevasse, snow management remained a primary consideration.
The Halley Research Station is located in one of the harshest environments on the planet. Winter temperatures typically are below -20°C (-4°F) with extreme lows of around -55°C (-67°F). The station is in 24-hour darkness for 105 days per year, and residents are completely isolated from the outside world by the surrounding sea ice.
Operations was a key consideration in selecting the new design, as any structure built in the Antarctic will be exposed to varying degrees of drifting snow. The accumulation of wind driven snow on and around such structures require extensive management to maintain a safe and accessible working habitat and, in some cases, also ensure minimal environmental impact on the surroundings.
We conducted comprehensive studies of the three designs using both water flume physical model studies and computational fluid dynamics (CFD) modeling. Available snowdrift information from Halley V was used, in both cases, to calibrate the analysis techniques. The results were then compared against a scoring assessment to evaluate the three designs.
We used our water channel to simulate snow drifting by introducing fine sand suspended in water flowing over the scale model of the study area. The sand particles carried by the water simulate snow particles carried by the wind over the actual site. Like drifting snow at full scale, the drifting sand particles are deposited in the wake regions downwind of the building and other obstructions.
Through further detailed analysis, we identified the long-term snowdrift patterns for each of the proposed designs, considering more than just a single event to take into account the cumulative effects, over an entire winter, of snowfall, varying wind directions, wind speeds, and temperature fluctuations.
Our evaluation of the snowdrifting characteristics of the three proposed structures enabled BAS to make a final selection with confidence. The Halley VI research station officially opened in 2012, and was the winner of the Engineering News-Record (ENR) Global Project of the Year in 2014. It is proving to be a robust solution to the problem of snow management as well as the other daily extreme challenges of living and working in the Antarctic environment. The station is scheduled for its first relocation in 2016-2017.