Model integration and validation

The module building process in Section 3 includes the integration process. This is a process for establishing the interface relationship between modules. Based on this, the integrated model should set the same number of ships, mechanics, maintenance policy, etc. The method is the same as the add process in section 3, but the model becomes visually complex as shown in Fig. 8. The simulation result of the integrated model should be able to simulate the real result as it is. Therefore, validation through robustness or sensitivity tests in DT is more important. The implementation of the functions included in the modules of Section 3 utilized the lookup function of the system dynamics tool (Vensim). The purpose of this study is to show that multi-physics and multi-scale problems can be solved by using system dynamics. In the DT building process, these lookup functions can be designed to be continuously updated during the simulation process. This is because the latest tools support data calibration using MCMC (Markov chain monte carlo) and link with programming languages ​​(python, R, etc.) or other analysis methods (analysis tools). For details, see Richardson (2015), Sücüllü, C., & Yücel (2014). The integrated model is shown in Fig. 8. Compared to the model in Section 3.3, it is visually more complex, but the model operation process is the same. The items additionally reflected in the model are as follows. The number of ships increased from 1 to 6. A virtual waiting space was applied because a queue may occur in the movement of the ship between the battle field and the repair shop. It was modified to handle normal failure and critical failure separately. And the night additional work of the mechanics was set to be possible up to 4 hours a day. The ages of the 6 ships are all different, and the ages of the actual naval fleet ships are applied. In the work of increasing the number of ships to 6, it is necessary to make sure that the priorities of entering the repair shop do not conflict, but it is not difficult. It should be noted that multi-physics support is possible. Although tangible and intangible physics such as ships, number of people, and manpower have their own scales, they interact with each other through causal relationships. Validation of some variables included in the DT model is shown in Fig. 9. All reflected variables must be checked one by one. All variables of the model reflected reality well.