The main purpose of this work is to simulate the flow of air and solid particles over a wildfire and to investigate the single and multiphase flow over the surface of a custom-designed wing with an Eppler-420 airfoil including an appendant custom-designed blended winglet. The wing is the result of a conceptual and preliminary design of a small-scale unmanned aerial vehicle (UAV) designed to assist in firefighting. The fire embers will be simulated in the Ansys Fluent commercial code as solid particles injected in the continuous phase, in an Euler–Lagrange approach. Primarily studied were the response of the model in air and air–solid flows, as well as the impact on aerodynamic efficiency due to the existence of the second phase. Moreover, the effects of unstructured, structured and mosaic poly-hexcore meshes are investigated and compared. The computational fluid dynamics (CFD) simulations, were implemented using a pressure-based solver, spatial discretization was conducted with a second-order upwind scheme, and the k-omega SST (k-ω SST) turbulence model was applied. Meanwhile, the two-phase flow was simulated using the Discrete Phase Model with reflect boundary condition on the surface of the wing and two-way coupling between continuous and discrete phase. To validate the results, experiments were conducted in a subsonic wind tunnel using a 3D printed model of the wing. The results show good agreement between simulations and experiments, with the structured mesh coming closer to reality, followed by the mosaic and unstructured meshes, respectively. Finally, a reduction in the aerodynamic efficiency of the wing section is observed, due to the presence of solid particles.

The correlation between computational fluid dynamics (CFD) and experimental fluid dynamics (EFD) is crucial for the behavior prediction of aerodynamic bodies. This paper’s objective is twofold: (1) to develop a method that approaches commercial CFD codes and their link with EFD in a more efficient way, using a downscaled model, and (2) to investigate the effect of rain on the aerodynamic behavior of a wing. More specifically, we investigate the one-phase and two-phase flow over a typical wing section NACA 641-212 airfoil, in the commercial code Ansys Fluent. Two computational models were developed; the first model represents the original dimensions of the wing, while the second is downscaled to 23% of the original. The response of the models in air and air–water flow were primarily studied, as well as the impact on aerodynamic efficiency due to the existence of the second phase. For the computational fluid dynamics simulations, a pressure-based solver with a second-order upwind scheme for the spatial discretization and the Spalart–Allmaras (SA) turbulence model were utilized. Meanwhile, for the two-phase flow of air–water, the discrete phase model (DPM) with wall–film boundary conditions on the surface of the wing and two-way coupling between continuous and discrete phase was considered. The second phase was simulated as water droplets injected in the continuous phase, in a Euler–Lagrange approach. The experimental model was constructed in accordance with the downscaled model and tested in a subsonic wind tunnel, using 3D printing technology which reduced the experiment expenses. The presence of water in two-phase flow was proven to deteriorate the aerodynamic factors of the wing compared to one-phase flow, as expected. The three-stage comparison of CFD and EFD results showed a very good convergence, in both single and two-phase flow. This can lead to the conclusion that a rapid and low-cost study for the estimation of the aerodynamic performance of objects with high accuracy is feasible with the suggested method.