A Practical Approach to Bulbous Bow Retrofit Analysis for Enhanced Energy Efficiency

Abstract

The bulbous bow is a significant feature integrated into ship designs to improve their overall performance. However, relying solely on original design assumptions may lead to suboptimal results, potentially hindering the vessel's efficiency during operation. To address this issue and optimize ship performance, this paper proposes a practical methodology for retrofitting the bulbous bow to suit the actual operational profile of container ships. By analyzing four years' worth of operational data, this study identifies the most frequent sailing conditions, including speed, draft, trim, and displacement. Using this information, multiple bulbous bow configurations by following Kracht (1978) are derived and subjected to numerical simulations, tailored to various sailing conditions. The proposed framework not only optimizes the bulbous bow for container ships but also extends its application to other vessel types such as bulk carriers, tankers, and large commercial ships. By customizing the bulbous bow design to match specific operational profiles, significant improvements in fuel efficiency, environmental sustainability, and overall operational performance can be achieved. This research underscores the significance of accounting for real-world operational conditions when designing and optimizing the bulbous bow. Leveraging operational data and conducting numerical simulations facilitates the identification of optimal configurations, aligning vessel performance with its actual sailing conditions. Implementing these optimized bulbous bow designs has the potential to revolutionize the maritime industry by enhancing ship performance and promoting energy efficiency. By prioritizing the practical considerations of real-world operational conditions, this paper presents a valuable approach to improve the overall efficiency of ships, contributing to a more sustainable and eco-friendly maritime sector. CFD, or Computational Fluid Dynamics, has revolutionized the process of bulb optimization. Before its introduction, research was primarily based on physical model testing. However, CFD has made it significantly easier and faster to refine bulb designs. This technological advancement has allowed for the incorporation of economic and ecological considerations into bulb design, going beyond just hydrodynamics (refer to Schneekluth et al 1998). This advancement enables engineers and designers to not only improve the hydrodynamic performance of the bulb, but also to take into account factors such as cost-effectiveness and environmental impact. As a result, bulb optimization has become a more comprehensive and efficient process, ultimately leading to better-designed vessels and a more sustainable approach to shipbuilding. The first serious attempts to improve ship design using CFD began during the previous decades which includes parametric design Lu et al (2016), Yang et al (2016), Peri et al (2001), Sharma et al (2008), Wagner et al (2014) and many others. A common characteristic among all of them is that the bulbous bow has a positive effect at higher speeds (refer to Schneekluth et al (1998)). In this paper, bulb optimization is presented as a measure to improve the energy efficiency of a container vessel in order to meet the Carbon Intensity Indicator (CII) criteria defined in Resolution MEPC.353(78) (2022). The concept of a CII within the shipping industry, designed to gauge and manage the carbon emissions associated with maritime activities, has emerged as a crucial tool in addressing environmental concerns and reducing the sector's carbon footprint. The aim of the measures is to improve the fleet average carbon intensity by at least 40% in 2030, relative to 2008 (refer to Resolution MEPC.377(80), (2023)).