# Using Digital Twin in a Shipbuilding Project
## 1 Introduction  
The European shipbuilding industry nowadays already faces competition from the Far East in a shipbuilding niche of passenger and cruise vessels and special purpose ships. Furthermore, it also faces the problem of the extremely high share of the shipping industry in terms of the rates of environmental pollution through greenhouse gas emissions and noise as a threat to living beings in waters [1]. Therefore, the shipyard is expected to find solutions to build safe, energy-efficient and environmentally acceptable vessels with high operational and maintenance autonomy (Smart ships) constructed in a sustainable business environment [2]. The market niches that the European shipbuilding industry is oriented to mostly have a demand for individual vessels or smaller serials of vessels, which additionally emphasises the shipbuilding company's profitability risks concerning the high complexity of the shipbuilding process, the high ratio of working hours in the cost structure of the process and the high portion of working capital [3]. The subjected challenges to competitiveness point to the necessity for improving shipyard's production process [4], management process [5], as well as developing technical-technological solutions during a vessel's design phase, thereby defining the efficient shipbuilding technological process [6]. Adopting Industry 4.0 doctrines is part of the strategy that most countries with a tradition and influence in the shipbuilding and maritime industrial sector in general have taken on [2], knowing that the digital technologies, development, research and innovation, are recognised as the most efficient tools for maintaining and, as expected, improving the competitiveness of the shipbuilding business systems [3]. Some of the previous research has defined and recognised Artificial Intelligence (AI), the Cloud, Big Data analytics (BDA) and the Internet of Things (IoT) as leading technologies in transforming traditional shipyardsinto Smart businesses, i.e., Shipyard 4.0 [3], while, for example, a Shipyard 4.0 case study by the Navantia shipyard in Spain emphasises Digital Twin or \"ship zero\" as the axis of the shipyard's digital transformation [7]. Digital Twin was initially introduced through the concept of monitoring the life cycle of the product (\"Product Lifecycle Management\") and defined by joining three \"entities\", i.e., (i) the physical product, (ii) its virtual equivalent and (iii) its data link (which actually represents digital technology, i.e., IT components) [8; 9], which can be, according to its original definition, considered as \"Digital Twin technology\", the core technology in realising Cyber-Physical Space [10]. Digital Twin, as a common notion, represents the virtual replica of the product, process, manufacturing system [11; 12; 13], object and other physical entities; such a replica is, with various sensors and software applications, connected to the physical entity, and with the data collected, it monitors the physical entity's performance parameters in real time throughout the entire lifecycle [10; 14; 15]. Figure 1 shows the Digital Twin conceptual model. A Digital Twin is either created as the replica of the already realised physical entity [16] or is developed along with the entity's design process by using 3D modelling technology [17]. In this study, the authors approached 3D modelling of the entity as the development of its Digital Twin, the same as has occurred in other researches on the topic of Digital Twin implementation in the shipbuilding processes [1; 15].