Hybrid dynamic grid generation technique for morphing bodies based on Delaunay graph and local remeshing

A hybrid dynamic grid generation technique for morphing bodies is presented based on Delaunay graph and local remeshing techniques. The initial stationary grids are generated firstly by the hybrid grid generator developed by the authors, in which structured body-fitted quadrilateral grids cover the domain close to the morphing bodies, adaptive Cartesian grids cover the outer computational domain and triangular grids fill up the gap between quads and triangles. With morphing of bodies, the grids close the bodies are firstly deformed with the technique of Delaunay graph proposed by Liu and Qin. If the quality of deformed grids are not satisfied the criterion or even crossing with each other, grid-remeshing is carried out locally. Hybrid dynamic grids over several morphing configurations are generated to validate the robustness of present grid generator, including a swimming fish, a pitching NACA0012 airfoil, a three-element airfoil with rotating flap, two swimming fishes, one and two clap and fling wings. Finally, coupled with the solver for unsteady incompressible flows, the hybrid dynamic grids are applied to simulating the unsteady flows over a swimming fish with different phase speeds, which demonstrates further the capability of numerical simulations for morphing aircrafts and unsteady Bio-fluid dynamics.