A way to improve the ghost-particle technique: the clone particles

In the present work we define a novel technique for the enforcement of boundary conditions along solid profiles. Thanks to the absence of interpolation nodes inside the fluid domain associated with the ghost particles, the proposed technique highly simplifies the mirroring procedure described in Marrone et al. [22] without jeopardizing the accuracy and the robustness of the overall approach. The novel technique, called clone particle technique, consists in two main steps. In the first one, the normal and tangent vectors to the solid profile are extended inside the solid body. Then, a local mirroring is applied, meaning that each fluid particle generates its own mirrored field over the solid particles placed inside the body. Unlike Marrone et al. [22], such a mirroring not only applies to the main fluid quantities but also works as a local correction to the normal and tangent fields in the solid body. Such a correction is enforced when the fluid particle is close to sharp profiles, in order to avoid that the fluid particle interacts with the normal vectors along the rear side of the angle/corner. This allows for a straightforward modelling of convex/concave angles and thin solid profiles. Numerical benchmarks at increasing complexity are considered to prove the reliability of the proposed technique. The results are compared and validated with other numerical methods, proving to be accurate and robust.