Tham khảo tài liệu 'applied computational fluid dynamics techniques - wiley episode 2 part 1', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | MESH MOVEMENT 241 the ring region between these two are allowed to deform. One can then either remesh this region or simply switch the diagonals. However simply switching diagonals will not always work as points that have slightly different radii will tend to overtake each other potentially creating very small elements. Thus the option of adding or removing points which is always possible with local remeshing should always be available. Figure . Simultaneous seat ejection . Applications The following section shows the mesh velocity fields obtained using the techniques described in this chapter for several examples. . MULTIPLE SPHERES The last decade has seen a continuous interest in the dynamics of bubbles or granular material immersed in a fluid. Figure shows a planar cut for a simulation with 36 spheres falling towards the bottom surface. As the spheres get close to the bottom wall they are removed automatically and the resulting voids are remeshed. Similarly new spheres are introduced at the top. One can clearly see the velocity field of the mesh movement. Note the almost constant contour levels close to the spheres which indicates that the mesh in the vicinity of the sphere moves almost rigidly. 242 APPLIED COMPUTATIONAL FLUID DYNAMICS TECHNIQUES a b Efl c Figure . Tanker Fleet a free surface and b mesh velocity in two planes c mesh velocity detail . PILOT EJECTION FROM F18 Every new generation of ejection seat must be tested for safe deployment. Figure shows a planar cut for a simulation with two pilots ejecting simultaneously Sharov et al. 2000b . As before the velocity field of the mesh movement displays almost constant contour levels close to the pilots indicating nearly rigid mesh movement. . DRIFTING FLEET OF SHIPS This case taken from Lohner et al. 2007c considers a fleet of tankers that are freely floating objects subject to the hydrodynamic forces of an incoming wavefield. The surface nodes of the ships move
