Computational Fluid Dynamics Study of Wing in Air Flow and Air–Solid Flow Using Three Different Meshing Techniques and Comparison with Experimental Results in Wind Tunnel

Abstract

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.

Measurements of the flow of a liquid–solid mixture/suspension through a segmented orifice

“…Insufficient quality of the computational grid in the conducted numerical simulations will result in erroneous results in the solution of equations during iteration and/or insufficient convergence in results . Whereas, a grid built of individual cells which are too small (fine-grained structure) excessively prolongs the time necessary to generate it and the duration of calculations themselves 30 – 33 …”

Comparing Design Schemes and Infection Risk Assessment of Negative Pressure Isolation Cabin

“…Tsz-Wun Tsang et al [32] mentioned three common ways to validate a model: (1) using experimental or measurement results obtained in a real simulated environment; (2) making use of experimental or measurement results in the literature; (3) adopting the benchmark model. In this study, the method of grid independence verification [33] is used to illustrate the accuracy of the CFD model to ensure that the mesh size is reasonable and does not affect the calculation accuracy.…”