![]() ![]() "Temperatures dipped just below freezing the night following the accident," Sharp told Live Science. The scientists found that temperature could greatly influence molasses's viscosity, or the degree to which it resists flowing. Once the tank collapsed, the molasses started flowing quickly over the waterfront. Boston winter temperatures would have cooled the molasses down, but it would still likely have been a few degrees warmer than the surrounding air, Sharp said. The molasses, however, had arrived from the Caribbean to top off the tank only two days before the flood, and was likely a balmy 50 to 68 degrees F (10 to 20 degrees C) when it was first delivered. The researchers found that at the time of the collapse, the air temperature would have been around 41 degrees Fahrenheit (5 degrees Celsius). "The goal is to take our knowledge and understanding of highly viscous spreading flows and apply that to the Boston Molasses Flood," Sharp said in the statement. The scientists also investigated the properties of blackstrap molasses, focusing on how temperature affected its rate of flow. "To gather relevant details about the flood and its aftermath, I've read hundreds of pages of historical accounts and contemporary newspaper articles, studied century-old maps of buildings in the area, and even called the National Weather Service to request historic meteorological data," lead study author Nicole Sharp, a Denver-based aerospace engineer and fluid dynamicist, said in a statement. “I’d expect there would be some crazy convective mixing going on, complicated by the fact that the viscosity of molasses changes substantially with temperature,” she says.Scientists began investigating the science of this disaster this year, after undergraduate students produced a video about the flood in May. Sharp hopes to expand her analysis to what was happening in the tank just before the eruption, when a warmer layer of molasses was pumped into the bottom. Much like quicksand, the more people thrashed about, the more deeply they found themselves trapped in the treacle. The initial onslaught left victims covered in suffocating molasses as rescuers struggled to save them, waist-deep in the goo. But once the tank ruptured and the molasses spread, it cooled quickly, making it even more viscous – and much more dangerous. On the fateful day, the molasses in the tank was slightly warmer than the surrounding air. Temperature also played a critical role in the aftermath of the flood. “Basically, you got bowled over by a tidal wave of molasses,” says Sharp, likening the effect to a sticky-sweet tsunami made of a substance 1.5 times as dense and several thousand times more viscous than water. ![]() The density of the molasses alone would account for the speed of its initial spread. It’s similar to how dense cold air will flow through an open door into a warm room, even if there is no wind to drive it. ![]() The true culprit: gravity currents, which come into play when a dense fluid spreads horizontally into a less dense fluid (in this case, molasses into air). Newspaper headlines speculated that a bomb may have caused the molasses to spread at such a rapid rate.įluid dynamics offers a better explanation. So, given the cold temperatures in Boston at the time, the extent of the flood was a puzzle. There’s a reason for the adage “Slow as molasses in January”. “It took several minutes just to pour 48 milliliters into a graduated cylinder,” Sharp says. In particular, the viscosity increases dramatically as the temperature drops, as Sharp and Kennedy found when they tested molasses in a cold room. Slow as molasses in Januaryīut when it’s cold, the stuff behaves more like a classic fluid. Molasses is what’s known as a non-Newtonian fluid of the shear-thinning variety, meaning it flows more easily in response to applied stress. ![]()
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