Aerodynamic Force Partitioning in Compressible Flows

We apply a compressible version of the Force Partitioning Method (FPM) to a series of test cases with increasing Mach number, ranging from low subsonic (Mach 0.4) flow over a NACA0012 airfoil to supersonic (Mach 3) flow over a circular cylinder. The method uses an auxiliary potential field as a weighting function to decompose forces into vorticity, density-gradient, dilatation, and viscous components via volumetric and surface integration around the body. Over this Mach number range, vorticity and density-gradient terms are identified as the major physical sources of aerodynamic forces, with density-gradient effects becoming progressively more significant with increasing Mach number. A key strength of FPM is its compatibility with established vortex detection and data-driven analysis tools. When combined with vortex identification algorithms, FPM enables local attribution of force contributions to specific flow structures, revealing how vortex merging acts as a precursor to intermittent, extreme drag events in the case of subsonic airfoil flow. Similarly, integrating FPM with Proper Orthogonal Decomposition (POD) links reduced-order flow representations directly to force generation mechanisms.