| Outline of Annual Research Achievements |
The final aim of the project is to develop an accurate adaptive multi-physics computational method for fluid-structure interactions (FSI) encountered in ocean/coastal engineering. The first phase of research was aimed to further extend our previously developed MPS-MPS code [1] to composite laminated structure modeling. Fundamental related studies were initiated as planned and an important aspect in this development was found to be related to precise implementation of fluid-structure interface boundary conditions. In order to thoroughly resolve this matter, a fully Lagrangian meshfree ISPH-SPH FSI solver was developed [2]. The key features of the developed ISPH-SPH correspond to absence of artificial numerical stabilizers, precise satisfaction of interface boundary conditions (with a developed coupling scheme referred to as FSA or Fluid-Structure Acceleration-based coupling scheme), high-level energy/volume conservation and potential adaptivity of the solver. Another target of the project is related to adaptivity (multi-resolution application), and in this regard, the potential adaptivity of fully Lagrangian meshfree solvers was portrayed with development of a multi-resolution MPS-MPS FSI solver [3].
[1] Khayyer, A., Gotoh, H, Falahaty, H., Shimizu, Y., Ocean Systems Engineering, 7, 299-318, 2017
[2] Khayyer, A., Gotoh, H, Falahaty, H., Shimizu, Y., Computer Physics Communications, 232, 139-164, November 2018
[3] Khayyer, A., Tsuruta, N., Shimizu, Y., Gotoh, H., Applied Ocean Research, 82, 397-414, January 2019
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
The developments achieved so far correspond to:
1. Development of an ISPH-SPH fully Lagrangian meshfree FSI solver with precise satisfaction of fluid-structure interface boundary conditions
2. Development of a multi-resolution MPS-MPS fully Lagrangian meshfree FSI solver characterized by high-level of stability and accuracy as well as precise satisfaction of interface boundary conditions
In addition, to achieve further progress and in order to tackle a long existing challenge in particle methods, namely, sensitivity of pressure/stress fields to regularity of particle distributions, a new scheme, namely, BM (Background Mesh) scheme [4] has been developed. The scheme enhances the pressure field calculation in projection-based particle methods through enforcing the continuity of calculated source terms at particles. Incorporation of BM scheme is expected to be helpful to achieve future aims of the project, namely, consideration of composite structures and inclusion of air phase into calculations. Related to another target of project, i.e. inclusion of air phase, leading to a water-air-structure multi-physics calculation, a new method is developed for simulation of multi-phase flows with high density ratios with material discontinuity [5]. A new algorithm comprising of Optimized Particle Shifting (OPS) is proposed to ensure stability, accuracy and consistency.
[4] Wang, L., Khayyer, A., Gotoh, H., Jiang, Q., Zhang, C. Applied Ocean Research 86, 320-339, January 2019.
[5] Khayyer, A., Gotoh, H, Shimizu, Y., Computers & Fluids 179, 356-371, January 2019
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| Strategy for Future Research Activity |
i. With the newly developed schemes, namely, FSA [2] and BM [4] schemes, incorporation of either a DEM (Discrete Element Method)-based contact algorithm or a stress point integration scheme need to be tested for rigorous extension of developed solver to contain composite (laminated) structures. In this regard, the main challenge, corresponding to precise satisfaction of interfacial boundary conditions (where material discontinuities occur) should be overcome and a reliable simulation should be achieved without any need for artificial numerical stabilizers that adversely affect the overall reproduced physics.
ii. In parallel to dealing with simulation of composite structures, extension of 2D solvers to 3D has been carrying out and some preliminary results are achieved that need to be rigorously validated and future related developments/validations would be of crucial importance to ensure reliable practical applicability of the solver. Indeed, precise, careful extension of 2D solvers to 3D is among the main aims of the project.
iii. As for multi-resolution, despite achievement of preliminary developments for multi-resolution MPS-MPS FSI solver [3], future developments must be made for SPH-based solvers and the issue of conservation and consistency for multi-resolution solvers need to be proved more mathematically with rigorous proofs as well as extensive, coherent validations.
iv. As for incorporation of air phase, the developed multiphase OPS [5] needs to be further extended and validated to tackle FSI simulations associated with violent fluid flows.
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| Causes of Carryover |
I had planned to purchase a DELL Precision 7820 Tower Processor Worksation which costs more than 400,000 yen and since the remaining amount of budget for FY2018 was not enough, this remaining budget was requested to be delivered to FY2019, such that this purchase will become possible in 2019. One of the reasons that enough budget was not available for workstation in 2018, was that I attended an international conference related to hydroelasticity in marine technology (presenting a paper directly related to this project) in September 2018 with the support of this fund.
The remaining amount will be merged with the fund granted for FY2019 to purchase a DELL Precision 7820 Tower Processor workstation for enhancement of computational performance of calculations.
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