Heritage conservation with a surface air curtain

Abstract

The conservation of cultural heritage artefacts often requires particular conditions and a bespoke setup. We investigate the use of computational fluid dynamics (CFD) modelling to obtain high-resolution data of the present setup to conserve the SS Great Britain: the first iron-hulled screw-propelled ocean-going ship, preserved in its original dry dock in Bristol (UK). The conservation efforts focus on the dry air curtain to maintain the hull at low relative humidity to prevent corrosion, hence avoiding further degradation. The proposed computational model captures the key features, enabling the study of the air curtain efficacy, retaining an overall uncomplicated setup which is seen to be robust in a sensitivity analysis. The analysis of the transport of dry air focuses on the near-wall region, hence the interface between fluid and solid surface, in which exchange of species occurs, such as humidity and temperature. The near-wall fluid dynamics is described by the wall shear stress, divergence of wall shear stress, surface shear lines and wall shear stress critical points. The results provide a complete description of the flow near the hull surface and identify regions where the air curtain maintains adequate protection. The investigation highlights the use of air curtains on solid surfaces together with the analysis techniques necessary to describe the fluid dynamics. The modelling assumptions proposed are shown to be effective in investigating the air curtain. The solution to the computational model is compared to sensor data, showing good agreement on the ship's hull.