Early-stage ship design is a complex, iterative process dealing with evolving requirements, interdependent decisions, and shifting stakeholder preferences. Unfortunately there is a lack of effective methods to express and track rationale behind naval architects' actions throughout concept development. This paper, thus, aims to address two research goals: (1) to develop a design rationale method to aid designers in the continuous capturing and reuse of design rationale during the collaborative concept design process, and (2) to evaluate how the developed design rationale method benefits collaborative design decision-making such that it leads to better insight into design issues across design teams and better concept designs over time for realistic ship design problems. To fulfill the first goal, a Surface Ship Design Tool (SSDT) was expanded and integrated with an extended Ship Design Rationale Method (SDRM). To fulfill the second goal, a multi-phase design experiment with two-person teams with ship designers from the Netherlands Materiel and IT Command (COMMIT) was performed to demonstrate the SDRM's long-term benefits on a frigate layout design problem with changing requirements. The results indicate that the developed SDRM can be used to capture design rationale in real-time during early-stage complex ship design. Lastly, the results of the case study show that the use of the SDRM effectively supports making explicit design decisions, because it seems to trigger participants to engage in more explicit design reasoning.
The description of the motion of fluid particles due to turbulence is highly complex and constitutes an unsolvable problem from the point of view of numerical methods. Therefore, it is necessary to use models based on different approximations, among which the Reynolds Averaged Navier-Stokes (RANS) time-averaged governing equations approach stands out. Since errors and uncertainty are inevitable factors when working with Computational Fluid Dynamics (CFD) models, rigorous verification and validation (V&V) procedures must be developed in order to assess the level of confidence in the results obtained. The application of the V&V process will allow, in practice, to select the RANS turbulence model that offers the best results based on the accuracy of the CFD calculations obtained. This paper discusses the suitability of 4 RANS models k-epsilon (Realizable), k-omega (SST), k-omega (GEKO) and Spalart-Allmaras to analyze the flow along a naval gas turbine exhaust duct. Hence, the goal is to find the turbulence model that provides the best results for the governing equations conservation and the approximation to the experimental flow model's coefficient of friction standpoint. The experimental friction coefficient (C (CF,EXP (CF,EXP) is obtained using a classical empirical correlation for fully developed turbulent pipe flow. The Reynolds number range (3.1 & times;105-1.2 & times;106) and the straight, smooth duct geometry fall within the correlation's validity, despite the elevated exhaust temperatures. In the absence of manufacturer experimental data due to proprietary constraints, this approach provides a well-established reference. The simplified duct configuration is intentionally chosen to enable validation against canonical empirical correlations.
New ship designs place an increasing demand on their electric power networks for defensive, sensing, and propul-sion systems. Precise numerical models of these electromechanical systems are computationally expensive. Behavioral modeling techniques offer an alternative that allows operators, engineers, and designers to rapidly simulate these power systems and gain platform insight. However, techniques in literature are restricted to radial, unidirectional power networks. This work presents microgrid behavioral modeling techniques that can handle AC, DC, and ring bus architectures in anticipation of the next generation of ship microgrids. A case study uses a ring bus power system similar to a U.S. Coast Guard National Security Cutter to demonstrate these techniques' ability to solve bidirectional, multi-generator systems quickly and usefully.
This case analysis is written to produce an active learning environment to increase the capability of acquisition/ program management professionals and senior leaders regarding program planning, decision-making, and affordability. Ballistic missile submarines (SSBNs) are a stealthy, survivable launch platform that contributes to strategic deterrence. Ohio-class SSBNs, which have filled the role of sea-based deterrence for the last 40 years, are nearing the end of their planned service life. To prevent a gap in nuclear deterrent capability, the successor to the Ohio-class, the Columbia-class, must be built to meet the Navy initial operating date requirements. However, the Columbia-class submarine is experiencing setbacks due to multiple issues with requirements, software development, funding, industrial base capacity and capability, and quality assurance with shipyards and manufacturers. This case analysis presents the Columbia-class submarine acquisition program and the future challenges facing the Navy. This research encourages critical analysis to increase the capability of acquisition sciences professionals regarding balancing of cost, schedule, and performance requirements within technical risk, shipbuilding capacity/ capability and affordability constraints. Affordability is always a major factor in development and procurement decisions for programs involving the development and integration of cutting-edge technologies and constrained by budgeted dollars. The case learning objectives include critical thinking, resource management, and problem-solving through stakeholder analysis, option analysis, and recommendations for the path forward.
The growing demand for low-emission energy in remote coastal and offshore regions has underscored the potential benefits of maritime nuclear systems. These systems offer a sustainable solution for continuous power supply at sea. However, their design must prioritize safety, producibility, transportability, and survivability to ensure a reliable operation in challenging environments. In this paper, a systems engineering approach is applied to conduct analysis of alternatives, parametric design, and survivability assessment of preliminary hull design for marine-based nuclear power plants. The results show that ships are more versatile than floating nuclear power plants, such as floating rigs and barges. Additionally, beam, draft, and center of gravity are among the key design factors for longitudinal stability. Furthermore, increasing the freeboard-to-depth ratio reduces the ship's vulnerability and allows it to balance both survivability and drag reduction.
