Validitation of the CFD Model based on the Euler Equations against the Experiment of Caradonna-Tung Rotor

This paper presents a validation study of a Computational Fluid Dynamics (CFD) solver based on the inviscid Euler equations. The aim is to assess the accuracy and applicability of a fast and efficient numerical method that can be employed in the conceptual design phase of a coaxial drone, developed by an undergraduate research group. For this purpose, the Caradonna-Tung rotor experiment—widely used as a benchmark in rotorcraft aerodynamics—is selected as the reference case for comparison. The rotor geometry consists of two straight blades with a constant chord, modeled using a symmetrical NACA 0012 airfoil. The rotor has a diameter of 1.143 meters and a chord length of 0.1905 meters. Numerical simulations were conducted at 1750 RPM with a collective pitch angle of 8°, under steady-state flow conditions. Euler equations were solved without including viscous effects or boundary layer modeling. A refined mesh was generated around the rotor to increase solution accuracy near the blade surfaces, particularly to better resolve pressure gradients. The computed pressure coefficient distributions were obtained for five spanwise locations (r/R = 0.5, 0.68, 0.8, 0.89, 0.96) and compared with experimental data. A generally high level of agreement was observed, particularly in the outboard blade sections (r/R ≥ 0.8), where the flow tends to behave more two-dimensionally. Minor discrepancies were noted near the leading edge and suction peaks, likely due to the lack of viscosity modeling in the Euler approach. Overall, the results suggest that Euler-based CFD methods can offer a low-cost and reliable alternative for early-stage rotor analysis. The validated model provides a solid foundation for future optimization studies and system-level performance assessments in coaxial UAV configurations.