1993 Fiscal Year Final Research Report Summary
Development of Numerical Simulation Method for Flows about Large-Scale Bodies of Complex Geometry
| Project/Area Number |
03555097
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| Research Category |
Grant-in-Aid for Developmental Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
船舶抵抗・運動性能・計画
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| Research Institution | University of Tokyo |
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Principal Investigator |
KAJITANI Hisashi Univ.of Tokyo, Faculty of Engineering, Professor, 工学部, 教授 (80010693)
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| Co-Investigator(Kenkyū-buntansha) |
NAKATAKE Kuniharu Kyushu Univ., Professor, 工学部, 教授 (70037761)
HIMENO Yoji Univ.of Osaka Pref., Professor, 工学部, 教授 (50081394)
KATO Hiroharu Univ.of Tokyo, Proffesor, 工学部, 教授 (00010695)
MIYATA Hideaki Univ.of Tokyo, Associate Prof., 工学部, 助教授 (70111474)
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| Project Period (FY) |
1991 – 1993
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| Keywords | difference method / boundary condition / free-surface / wave breaking / flow separation |
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| Research Abstract |
We have difficulties in generating grid system for the simulation of large-scale body of complex geometry. Similar difficulties also exist in the simulation of nonlinear 3D deformation of free-surface such as wave breaking phenomenon. The objective of this research is to solve these problems by developing a new method of numerical simulation. A rectangular inflexible grid system is employed and the body boundary conditions are approximately implemented. The free-surface condition is implemented by the newley-developed marker density technique. A scalar value of marker density is defined in each cell and it is moved by the equation of free-surface movement. Although the surface tension and the viscous stresses are ignored on the free-surface, strongly interacting free-surface flow due to gravity is well simulated with the simultaneous solution of the motions of air above the free-surface. The MAC type time-marching simulation procedure is employed for the fulfilllment of time-accuracy.
The technique of complex geometry is examined by the simulations of a flow past a sphere, a flow past an automobile. This demonstrated that this technique is suitable for flows of which separation point is clear. Since equal spacing is used the degree of resolution is superior in the far-field where a separated flow show interesting structure.
The technique of density function for the free-surface has the disadvantage of diffusing the interface. However, by using proper difference method for the equation of movement the degree of accuracy becomes satisfactory for practical problems of engineering interest. This technique is applied to the problem of 3D wave breaking flow about a bow of a full ship with sufficient agreement with the measurement.
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