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- Type of Document: M.Sc. Thesis
- Language: Farsi
- Document No: 41838 (08)
- University: Sharif University of Technology
- Department: Mechanical Engineering
- Advisor(s): Seif, Mohammad Saeed; Nouri Borujerdi, Ali
- Abstract:
- A finite volume algorithm to assess hydrodynamic aspects of a rigid and up to three degrees of freedom marine structure in the context of transient two-phase flow o viscous incompressible fluids is presented. Different components of the algorithm are selected just after a complete review of all probable choices. Using a collocated arrangement to save data, a fractional step method is applied to satisfy Navier-Stokes and continuity equations, as an appropriate choice in transient flows. Also, a volume fraction transport equation is solved to capture large and complex deformations of the interface between two phases. So, an effective fluid is introduced by combining two immiscible phases in the whole domain based on their availability in control volumes. Besides, an overlapping mesh system including a nonuniform Carsesian background mesh as well as one/two overset meshes of quad cells is implemented to deal with the computational domain. So, the body-attached boundary-fitted overset meshes follow all motions of their related structures in the domain while the background mesh is fixed during the computation. The overlapping mesh system is actually a good choice to investigate six degrees of freedom rigid body motions and relative motions without limitation in motion amplitude. It must be remembered that, the rigid body motion equations are solved to calculate linear and angular motions of a structure due to loads exerted on the structure from to flow field. A two dimentional code is developed based on the algorithm to run differet case studies with more attentions on the wave generation, while the proposed algorithm is potentially three dimentional. The wide range of researches consist of cavity flow, unsymmetrical flow around a cylinder in a channel, Airy wave, plunger type wave maker, slamming of a cylinder and finally motions of a floating structure in front a flapping-type wavemaker. Therefore, all parts of the algorithm are precisely evaluated. Results are generally in good concordance with available date and capability of the algorithm is obvious. Although examinations are all two dimensional, two-phase flow simulation using an overpallaping mesh system is the noticeable innovation of the thesis according to the knowledge of the author. Besides, a non-conservative interpolation scheme is introduced to exchange information between meshes which reduces the sensitivity of cell sizes to each other in overlap zone. It must be mentioned that, an interpolation scheme is also initiated to approximate the value of pressure on faces of cells in the vicinity of the interface because there is neither sharp interface between phases nor a surface reconstruction method. The algorithm is also a fresh combination of different choices. It seems that the algorithm is a fine core towards developing a three dimensional numerical laboratory in hydrodynamics
- Keywords:
- Numerical Hydrodynamics ; Free Surface ; Overlapping Grid ; Finite Volume Numerical Method ; Finite Volume Discretisation Method
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