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We present an image-based pipeline for generating geometrical digital twins (GDTs) of stone masonry elements with detail down to the stone level. For this purpose, we acquire RGB images of the individual stones and of the wall during the construction phase. In our framework, we use structure from motion (SfM) to first generate 3D source and destination models, which are then registered to form the GDT through non-linear least squares and 2D point feature correspondences detected on the SfM images. This method contrasts with traditional techniques that register point clouds using 3D point descriptors. Because of the robustness of image feature descriptors, we found that using 2D instead of 3D point features facilitates the automation of the GDT generation. To benchmark our algorithm, we compared the results through an Euclidean–distance-based proposed metric with a known 3D textured model from which images were synthetically generated. We show the robustness and feasibility of our method for full size elements, wherein GDTs were generated for dry-stone and stone-mortar systems. This study allows researchers to produce accurate representations of the 3D geometry of walls built for experimental research, reducing therefore uncertainties related to the stone size, shape and arrangement to a minimum when comparing 3D numerical simulations of these walls to experimental results. Codes and data sets are publicly available (https://github.com/eesd-epfl/stone_masonry_GDT and https://doi.org/10.5281/zenodo.7266587)., Automation in Construction, 145, ISSN:0926-5805

Experiments were conducted to study the performance of circular and square tank surface aerators on the oxygen transfer coefficient and to a limited extent on power requirements. All the tanks are geometrically similar except for their shapes. They consist of a rotor of diameter, D, fixed with six flat blades rotating with a speed, N, in pure waters of viscosity, υ, at room temperature. A simulation equation to predict the oxygen transfer coefficient, k = KLa20(υ/g2)1/3 for any given dynamic parameter governing the theoretical power per unit volume, X = N3D2/(g4/3υ1/3) was developed for circular tank aerators. The data on square tank aerators support another such simulation equation developed earlier for square tanks. A comparison of results, while re-aerating the same volume of water in both the shapes of tanks, leads to the interesting conclusion that for a given rotor speed the oxygen transfer rate is substantially more in square tanks than in circular tanks; whereas for a given effective input power to the rotor the oxygen transfer rate is more in circular tanks than in square tanks. This suggests that square tanks are preferred to circular tanks to raise the oxygen concentrations at a faster rate, whereas the circular tanks are advantageous as far as power requirements are concerned.