Investigation into Propulsive Characteristics of an Inland Vessel in Confined Waterway

Small to medium inland navigation vessels (CEMT Classes I to IV) are considered as a viable alternative cargo transportation mode to relieve loads on some of the most congested European motorways. In the Horizon Europe project AUTOFLEX (https://autoflex-vessel.eu/), a novel type of autonomous inland cargo vessel is being developed, which can carry out transport services in previously underused confined waterways. Confined waterways, characterized by limited depth, width, or both, significantly affect vessel hydrodynamics. In such conditions, vessels experience increased resistance, along with notable changes in sinkage and trim compared to operation in unbounded deep water. Furthermore, interaction with waterway boundaries affects considerably the inflow experienced by the propulsor.
The model‐scale experiments remain the most common approach to predicting ship’s resistance and propulsive characteristics; and the extrapolation procedure based on the ITTC 1978 performance prediction method is commonly employed. However, the validity of this approach in application to inland vessels in shallow water conditions is subject to criticism (Mucha et al., 2017). The Lackenby (1963) method, also described in ITTC (2014), shows limited applicability across diverse hull forms due to its reliance on limited experimental data and thus exhibits constrained applicability across diverse hull forms and operating conditions. The form factor concept originally proposed by Hughes (1954), and refined by Prohaska’s method (ITTC, 2002) separates the wave resistance component (which depends only on Froude number, 𝐹𝑟) and viscous resistance (which depends only on Reynolds number, 𝑅𝑒). The form factor, which is assumed independent on both 𝐹𝑟 and 𝑅𝑒 accounts for the additional viscous resistance attributable to hull shape beyond flat‐plate friction. This very assumption has been subject to criticism in many studies, numerical, as well as experimental, with first systematic results opposing the main form-factor hypothesis presented in ITTC (2008). More recent studies (Zeng et al., 2020) have also demonstrated that, for depth‐Froude numbers 𝐹𝑟ℎ>0.5422 and non‐slender hulls, the wave resistance dependence on 𝐹𝑟 alone may not hold. Furthermore, the assumed linear dependency of wave resistance coefficient on 𝐹𝑟4 may not be observed for various hull geometries (Korkmaz et al., 2021). In general, scale effects in shallow water are expected to be become more pronounced with decreasing water depth, since at lower depths, boundary layers on the hull and channel floor experience stronger interaction as illustrated by CFD analyses presented in Krasilnikov et al. (2025). At very low depths, the said interaction has appreciable influence on wave systems generated by the ship due to changes in pressure distribution over the hull. With these considerations in mind, it is easy to understand the results presented by Raven (2019) which demonstrated that traditional model‐to‐ship extrapolation methods can overestimate water‐depth effects unless a depth‐dependent form-factor is employed. A revised procedure for correcting full‐scale speed trials to account for water‐depth effects has been proposed, and it is now included in the ITTC guidelines (ITTC, 2017).
The primary purpose of the present study is to investigate by means of CFD simulations, the influence of limited water depth on ship’s towing resistance in full‐scale, and to illustrate differences from the equivalent test conditions in model scale. The numerical setup is based on the methodology presented in Krasilnikov et al. (2025). The ultimate objective is to establish a validated framework that aids further investigation of vessel propulsive performance in inland waterways.