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Ito, Kei; Kunugi, Tomoaki*; Ohshima, Hiroyuki
International Journal for Numerical Methods in Fluids, 67(11), p.1571 - 1589, 2011/12
Times Cited Count：9 Percentile：48.01(Computer Science, Interdisciplinary Applications)In this paper, a high-precision unstructured adaptive mesh technique for gas-liquid two-phase flows is developed and verified/validated. In the unstructured adaptive mesh technique, the PLIC algorithm is employed to simulate interfacial dynamic behaviors and, therefore, the reconstruction method for the interfaces in refined cells is developed, which satisfies the gas and liquid volume conservations and geometrical conservations of interfaces. In addition, the physics-based consideration is performed on the momentum calculations near interfaces, and the calculation method with gas and liquid momentum conservations is developed. For verification, the slotted-disk revolution problem is solved and the unstructured adaptive mesh technique succeeds in reproducing the slotted-disk shape accurately. The dam-break problem is also simulated and the momentum conservative calculation method succeeds in providing physically appropriate results, which show good agreements with experimental data.
Shinohara, Kazunori*; Okuda, Hiroshi*; Ito, Satoshi*; Nakajima, Norihiro; Ida, Masato
International Journal for Numerical Methods in Fluids, 58(2), p.119 - 159, 2008/09
Times Cited Count：3 Percentile：20.15(Computer Science, Interdisciplinary Applications)An adjoint variable method was formulated and applied to minimize the fluid drag on a 3D object placed under a Stokes flow condition. In the present formulation, a smoothing method for the surface mesh, a method to guarantee the constant volume condition, and a mesh relocation technique base on the biharmonic equation were incorporated, which are crucial in realizing stable and robust shape optimization. The governing equations were solved using a finite element method on moving meshes. To overcome such difficulties as heavy computational burden and large memory requirements, the presented code was implemented with the data compression technology supplied with the software library HEC-MW. Also, by utilizing the HEC-MW, the code was efficiently parallelized and the number of program lines was dramatically reduced. Using the developed code, the fluid drag on a straight cylinder was reduced by about 25% under a Stokes flow condition.
Muramatsu, Toshiharu; Yagawa, Genki*
International Journal for Numerical Methods in Fluids, 54(6-8), p.805 - 830, 2007/07
Times Cited Count：0 Percentile：0.02(Computer Science, Interdisciplinary Applications)An adaptive control system to yield optimum time step sizes was developed using the fuzzy theory for transient multi-physics numerical simulations. Applications of the control system reveals considerable amount of the computing time savings, typically by 50 % to 75 % of the computing time required when the time step size was not controlled by the system. The result obtained in this work is very encouraging in the sense that the adaptive control system would be used as one of the efficient measures for saving computing time when one wishes to perform extremely large-scale computations in transient multi-physics numerical simulations.
