MONSOON STEEL Sri Lanka Samanalawewa Archaeological survey and excavation over a number of years revealed a major industry (80+ sites) of the 7th and 11th centuries AD, based on a wind-powered linear furnace design Reconstructed furnace from archaeological evidence Experimental smelts in 1994 and 2007 mid-smelt - 1994 towards end of smelt - 1994 Flow of air and flame up the front wall - 2007 Smelting at night Smelting at night gave clues to the complex air flows through and over the furnace Breaking apart the furnace and slag to retrieve the metal ‘blooms’ Metal products of smelts Analysis showed this to be high quality high-carbon steel High-carbon steels and Damascus swords At the time the wind-powered furnaces of Sri Lanka were producing high-carbon steel the Early Islamic writer al-Kindi praised Sarandibi steel as one of the most desirable for sword-making Data visualisation Data sets • wind direction and velocity for region and macro-environment • wind direction and velocity for site-level environment • wind velocities at furnace level during experimental smelting • furnace temperatures at tuyere (air inlet) and charcoal bed during smelting • ore and charcoal fuel charging weights and rates • tap slag running times The results of the field experiments were published in Nature (379, 1996) Tangible and Intangible Archaeology Collected hard evidence – slag waste, metals, furnace remains, experimental experience, images, data How do we ‘capture’ the fugitive but critical evidence of natural and managed air flow and combustion? How do we visualise it and importantly use it as a tool for further research? First interpretation of air flow through furnace based on observations and recorded data (furnace cross-section) Further research using computational fluid dynamics (CFD) at Exeter refined the initial analysis. Paper with Gavin Tabor published in Journal of Archaeological Science Arrangement of instruments to measure temperature Computation of all temperature readings across furnace through duration of smelt (Matt Baker) Further applications: other furnace technologies Sri Lanka: small, bellows-driven shaft furnace last used in early 20th century Well-recorded example with archaeological, ethnographic and documentary records Furnace shape and size reconstructed from excavation and written accounts Experimental example built and run in Exeter by engineering students (MJ Baker, R De Salis, D Dawson) CFD analysis of airflows including quasi-sinusoidal flow model THANK YOU