Analysis of far-field thermodynamics formulation for drag decomposition in unsteady flows

An aerodynamic engineer must develop solutions to reduce drag, create more efficient aerodynamic devices and decrease fuel consumption to achieve a sustainable project. A CFD solver can break down aerodynamic drag into two main phenomena. It computes the pressure field and shear stresses at the walls, then integrates these values over the body. However, the engineer must understand the specific sources of these phenomena. In addition to drag computation at the wall, known as the near-field method, far-field methods have been studied since the early 20th century to capture more phenomenological information, such as drag due to viscosity, shock waves and induced effects. This study will analyze a specific unsteady far-field method developed by Toubin, implemented in StarCCM+. It is a momentum-based approach with a thermodynamic formulation for far-field drag decomposition in unsteady flows, focusing also on the definitions of domains where the sources of drag occur. Several test cases are conducted to assess each drag contribution individually and then examine their interactions.