Documenting and analysing to preserve: An integrated approach between laser scanning and Computational Fluid Dynamics. The case study of the column of the temple of Hera Lacinia near Crotone

The study presents the results of a multidisciplinary research that integrates terrestrial laser scanning (TLS) and computational fluid dynamics (CFD) to document and analyse an archaeological asset subject to natural hazards. The experimentation was conducted on the surviving column of the temple of Hera Lacinia, located in Capo Colonna near Crotone (Italy). The column, the fragments of the crepidoma and of the foundation constitute the most visible remains of the peripteral Doric temple (second quarter of the 5th century B.C.), belonging to the most important sanctuary of Magna Graecia. The temple, the sanctuary and the other ancient buildings, which are in the area of the Capo Colonna promontory, were destroyed over the centuries to obtain construction material. Today the column and the remains of the temple are located inside the National Archaeological Park of Capo Colonna, protected from human action, but subject to natural phenomena which are dangerous or potentially dangerous in the long term. The wind exerts a constant erosion of the surface of the column and wear of the lower part of the shaft due to the continuous oscillations to which it is subjected; moreover, the wind thrust could add up to a possible seismic action. On the other hand, the geomorphological evolution of the promontory (coastal erosion and subsidence) causes the coastline to recede, and is responsible for landslides affecting the column-basement system. Starting from the point cloud acquired by the TLS, a mesh of the column, basement and surrounding terrain was created, aimed both at documentation, graphic analysis and CFD. The survey enabled the description of the current state of the column-basement system, documenting and measuring the shapes of the column, as well as the different inclinations of the individual parts caused by instability of the ground. Furthermore, the CFD model of the Hera Lacinia column was developed. The model is based on the three-dimensional Reynolds-Averaged Navier-Stokes (RANS) equations with the k-ε closure turbulence model. The oncoming wind was modelled according to the results obtained from 70 years of statistics analysis (from 1950-2021) of wind hourly data (streamwise and spanwise components). The interaction between wind flow and the Hera Lacinia column geometry shows very complex phenomenona. The adopted numerical model was able to simulate correctly the main phenomena involved such as the flow separation occurring around the column as well as the wake behind it. Particular attention was paid to investigating the most damaged areas of the column, identified by analysing recent images of the column, where the values of the time-averaged drag and lift forces were obtained. In order to obtain the erosion-based damage prediction future research will focus on the analysis of air flow erosion of the Hera-Lacinia column, starting from the measurements in situ of the main air characteristics and using the latter as the fluid for the numerical simulation, and by also considering different values of wind speed and directions.