The Studies Of Receptivity Problems And Parallel Numerical Simulations For Jet Secondary Breakup Interfacial Problems

Two aspects were investigated in this dissertation: one for Poiseuille pipe flow receptivity problem, another for jet secondary breakup parallel numerical simulations.The receptivity problems study the responses of the fluid systems when certain exterior forces were exerted on. Research statuses were discussed to derive an all-around knowledge about receptivity problems. And asymptotic methods were applied to an acoustic wave driven Poiseuille pipe flow, whose wall has geometric irregularities, to establish a receptivity problem. Bi-orthogonal eigen-function systems were assigned to launch such a sophisticated problem, and Chebyshev collocation method gained its power in the numerical procedures. A model problem addressed to have found the non-similarity character of Poiseuille pipe flow observed in experiments of Leite(1959).Level-Set method was utilized to capture the moving interfaces of drops. For Level-Set function re-initialization procedure, which plays a vital role in Level-Set interface capturing method, was re-investigated. The re-initialization procedure here was accomplished through fixing the interface positions using interpolation techniques, and tactical arrangement of numerical stencils was assigned. The examples show the better performance of fixed interface method here on volume maintenance when compared with the generally used method of Sussman,et al.(1996).Jet secondary breakup parallel calculations were carried through on the cluster-style supercomputer SUHPCS(Shanghai University High Performance Computer System). Decomposition area method of coarse granularity adopted to parallel our serial codes.In the modeling of Secondary breakup simulations, a new method was created to give an initial flow field detailed in section 7.2.2, which can satisfy the continuum equation without streamlines cutting through the drop area what not achieved for both in other's simulations. And also the moving grid method was used to track the undetermined computing area.Through numerical simulations three breakup modes referring to as the oscillation mode, the bag mode, the shear mode and some transitional modes were derived. Results show that high gas velocity and small surface tension increase the probability of drop breakup, while viscosity has less effect on breakup modes when the relative velocity between liquid and gas is great. The density ratio is also important. The big density ratio tends to narrow breakup mode transitions. From ReL ~ We parameter spaces, a band-style distribution of three breakup modes is found, the bands have less sensitivity to ReL, what have perfect consistence with experiment observationsand other's results. Besides the simulations of g = 10, 1 / g = 100 and t / g = 1000 werealso considered. To our knowledge, there are few works about secondary breakup simulations, and the Level-Set method used to this object hasn't been met before, and also the secondary breakup simulations of density ratio exceeding 100 haven't been found, so the work here is a new try.In addition, many aspects about jet atomization were addressed to derive detailed descriptions, which included the industry background, experiments, theoretical researches and so on, and tried to get cognition of jet atomization problems clearly.