DNS approach to Turbulence and Vortex Dynamics in compressible and incompressible Fluids

The fascinating behavior of fluids has always caught people attention. In this framework, the dynamics of turbulence and vortices can be observed in everyday phenomena, such as clouds, smoke, etc. However, contrary to what might seem intuitive, these occurrences have complicated behaviors that are difficult to be predicted by a simple linear equation.
It is generally recognized that the Naiver Stokes equations can describe fluid motion. The complexity of the issue of fluid motion requires numerical methods to be used, giving rise to the “computational physics”. This field is undergoing rapid evolution, involving all areas of science, including physics, biology, chemistry, and so on... The primary objective of this branch of Science is to resolve the partial derivative problem using a numerical model that allows an approximate answer to be produced. The consistency of the numerical solution with actual experience and experimental observation is worthy of additional attention. In fact, each numerical model needs to be validated before it can be used for a certain application.
In the context of engineering, the study of turbulence generated by the interaction of a fluid flow with an object is especially relevant. The cylinder case study gained significant importance in both experimental and numerical approaches. This problem depicts how a fluid flow interacts with a pile, a bridge, an airplane wing, etc. Consequently, in this perspective, this thesis focuses on numerical studies concerning the force and vorticity generated around a cylinder in compressible and incompressible conditions.
In particular, DNS (Direct Numerical Simulation) was chosen rather than other turbulent models in order to focus the investigation on the turbulent phenomenology. This caused a serious issue with the study of numerical stability and the length of time required to run a simulation. For this reason, to limit computational times, it was decided to use Python and C++ environments.