## 1 Introduction  
Despite advancements in technology, pool fire accidents still occur and cause substantial personnel harm and asset damage [1]. Operational ships and offshore installations are particularly prone to fuel spillage owing to several factors, such as equipment ageing and human error. As ships and offshore installations have numerous ignition sources, including hot surfaces and electric devices, there is the potential for pool fires to occur. Spillages that occur on ships and offshore installations under motion may form larger pools than in onshore events. As the heat release rate (HRR) of pool fires depends on the fire surface area, the fire consequences are expected to increase with the spreading extent of the spilled pool. Moreover, structural members that are not subjected to thermal loads under uninclined conditions may be affected under inclined conditions owing to the increased pool dimensions. In large compartments, which can be found in roll-on/roll-off (ro-ro) ships and aircraft carriers, fuel spillage accidents are more likely to result in increased pool spreading, as shown in Figure 1. Small compartments limit the spreading extent of spilled fuel, and for extreme cases, it can be assumed that the pool covers the whole compartment. However, this assumption would be inaccurate for large compartments, as the pool is unlikely to cover the whole compartment. The current Safety of Life at Sea (SOLAS) rules concerning the fire safety of ro-ro spaces address a wide range of functional requirements on subjects such as fire protection systems, ignition sources, and ventilation. However, the effects of deck inclination on pool fires and the related safety measures are not addressed [2]. As the basic design of firefighting systems in large compartments is based on the existing SOLAS rules for ro-ro ships, current measures may not be applicable to pool fires under inclined conditions. Therefore, the effects of substrate inclination on fire consequences need to be understood to enable correct assumptions for the fire design of ships and offshore installations. Methods for determining fire loads on ships and offshore structures have been actively investigated [3; 4; 5; 6; 7], along with the responses of structures exposed to fire loads [8; 9; 10] and efficient fire suppression system design principles [11]. Additionally, although large spaces have been studied [12; 13; 14], previous studies did not consider pool spread characteristics under ship motion. As the fuel spread behaviour may be strongly affected by ship motion, and pool fire characteristics depend considerably on the pool shape and size [15; 16; 17], the fire consequences under ship motion cannot be accurately determined using the existing methods. In contrast, the characteristics of onshore spillages have been extensively investigated. The spilled pool area on substrates without inclination can be predicted using the kinematic viscosity and fuel spill rate [18; 19]. [PERSON] et al. [20] investigated fuel spillages on inclined pavements. However, these authors did not establish formulae for predicting the spill shape and focused only on instantaneous spillages. [PERSON] and [PERSON] [21] experimentally investigated spillages inside tunnels and found that the pool breadth was dependent only on the spill rate, and the inclination angle of the substrate could be assumed to have no effect. Their findings were subsequently verified [22]. However, the suggested formulae are not applicable to large compartments, as the studies focused on spaces with limited road width. [PERSON] et al. [23] investigated the spilled pool area and velocity characteristics of flammable fuel spilled on inclined porous substrates. Additionally, the spread and evaporation behaviour of liquefied natural gas (LNG) have been explored [24; 25]. [PERSON] et al. [26] comprehensively reviewed relevant methods for predicting fuel spillage behaviour. Moreover, the pool fire characteristics on inclined surfaces have been experimentally investigated [27; 28].