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Shallow water studies of ship hydrodynamics typically examine a single, constant underwater canal cross-section at a time. In practice, the underwater cross-sectional area and shape of the waterway is rarely, maintained constant over long distances. This study presents an attempt to quantify the effects of an abruptly varying water depth by numerically modelling such a condition using CFD. The results show that waves propagate and refract in the numerical towing tank in a physically consistent manner showing less than 0.1% error in the dissipation of a solitary wave when compared to analytical relations. A strong boundary layer is formed on the canal bottom almost as soon as the ship enters the shallower region. The resistance increase, resulting from the depth change is up to approximately 226% of the initial value near critical speeds.

Vessels can operate in unpredictable environments depending on the geographical area and weather conditions. One example of conditions a vessel might not be assessed against is the presence of depth- varying currents, which are particularly relevant in confined waters where currents can be created due to tidal influences, or short fetches in inland waterways. The possible presence of depth-varying currents motivates a numerical assessment of the effects of sheared currents on the hydrodynamic performance of the KRISO Container Ship (KCS) in confined waters. The results highlight that exploiting currents, such as those generated by tides could be used to improve the energy efficiency of vessels considerably. These currents present significant possibilities for voyage optimisation based on geographical and meteoro- logical conditions. The results specific for the KRISO container ship point to resistance reductions when the current assists ship motions, accompanied by considerable decreases in sinkage and trim. Conversely, when currents oppose ship motion, resistance, sinkage and trim can increase by a factor of 3 depending on the strength and shape of the depth-varying current. The results also show that a current with constant vorticity, a case frequently used in the literature to investigate the impact of sheared currents, creates the biggest increase and decrease for inhibiting and assisting currents, respectively., peer-reviewed

In this study, the forces and moments acting on the KCS ship model as a result of oblique towing at 10 and 20 degrees drift angles are evaluated experimentally and numerically via a commercial Reynolds averaged Navier-Stokes solver. For the purposes of this work, the KCS hull is modelled both experimentally and numerically at a scale factor of 1:75. The adopted case-studies feature both horizontal and vertical restrictions. Thus, the subject of this work is the oblique motion of a ship in a narrow canal with a depth of h/T = 2.2. The relative impact of turbulence modelling is assessed by comparing the computed integral quantities via several eddy-viscosity closure strategies. These include significant variants of the k-ϵ and k-ω models as well as a widely used one-equation closure. Multiphase numerical simulations are performed at several of the experimentally investigated depth Froude numbers for each drift angle condition in order to fully capture the physics of the problem at hand. The present study aims to provide a quantitative evaluation of the performance of the adopted turbulence models and recommended the best closure strategy for the class of investigated problems.

The increasing relevance of simulation-based design has created a need to accurately estimate and bind numerical errors. This is particularly relevant to full-scale computational ship hydrodynamics, where measurements are difficult and expensive, simultaneously requiring a high degree of predictive accuracy even in early design stages. However, the field of ship hydrodynamics has yet to fully exploit the enhanced capabilities and potential benefits numerical verification methods have to offer. The present study presents a detailed application of numerical verification procedures in CFD as applied to local parameters, such as free surface elevation and skin friction. This is done in order to pinpoint specific locations in the computational domain responsible for heightened levels of error and uncertainty. Relationships between different parameters are demonstrated and discussed based on a set of full-scale simulations of the KCS advancing through a canal using CFD.

With the rapid advent of computational methods in all fields of engineering, several areas have emerged as significant sources of ambiguity. Among these is the selection of a turbulence model to close the Reynolds averaged Navier-Stokes equation. In ship hydrodynamics, this has been particularly difficult to resolve due to the complex nature of the problem. Furthermore, there are a wide variety of turbulence models all claiming superiority. Thus, navigating to the correct choice is a subject of experience. The present study aims to alleviate the ambiguity inherent in the field. This is done by performing a series of tests on the turbulence models and comparing the integral outcomes with experimental results. Specifically, shallow water cases are chosen due to the additional layer of complexity associated in the prediction of parameters of interest. The results are analysed via a modified bivariate plot, which reveals a strong candidate for the optimum choice of turbulence modelling. The assessment simultaneously takes into account resistance and sinkage, in addition to consistency across different case studies. The time per iteration also points towards the same candidate, identified as the standard k-ω model, as a good choice within the software used to perform the analysis. The results also suggest that pressure resistance and its constituent components are not coupled with the turbulence model. On the other hand, frictional resistance is highly dependent on the closure selected and is identified as the main contributor to deviations with regards to experimental values.

In international shipping, there are several waterways that are widely viewed as bottlenecks. Among these is the Suez Canal, where recent expansions have taken place. Although the Suez Canal has a high importance in international shipping, little research has been carried out in maximising the number of ships capable of traversing for a set period of time. The present study aims to examine hydrodynamic phenomena of ships advancing through the Suez Canal in the allowed speed range to determine the relative effects of the canal depth and/or width restrictions on the overall ship sailing performance. A rectangular canal is also included as a reference to gauge the effects of varying canal cross-section. The present study combines experimental, numerical, analytical and empirical methods for a holistic approach in calm water. As a case-study, the KCS hullform is adopted, and analysed experimentally, via Computational Fluid Dynamics, using the slender body theory, and empirical formulae. The results reveal strong coupling between the canal's cross section and all examined parameters.

A numerical simulation method is presented by integrating Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) solvers to predict ship wave loads and slamming loads taking into account hydroelastic effects. The interest of this study mainly lies in the slamming and green water pressures acting on a flexible ship investigated by the coupled CFD–FEA method. Firstly, verification and sensitivity analysis of the wave loads and slamming pressures on the S175 containership evaluated by the coupled CFD–FEA method is conducted by comparing the results using different mesh sizes and time step schemes. Discussion on the effect of hydroelasticity on impact pressures is also conducted. Then a comprehensive analysis on the global motions, wave loads, slamming and green water pressures of the ship in different regular wave conditions is undertaken. Finally, a simplified bow flare and bottom slamming pressure estimation method based on the seakeeping data of incident wave and ship global motions are proposed, which can reduce the computational burden of the two-way fluid-structure interaction simulations when impact pressure is concerned.

Although there is a significant body of research devoted to the shallow water hydrodynamic aspects of ships, several unexamined topics remain. Among these is that of critical outer flow in a dredged channel and its influence on parameters of interest. While empirical methods can be used with ease to resolve this, they can provide results with reliability sufficient only for an early design stage. On the other hand, more sophisticated potential flow theories are either inapplicable or do not perform well at the critical limit. However, RANS (Reynolds Averaged Navier-Stokes) – based tools can accurately capture all underlying phenomena without relying on limiting assumptions. This paper presents an attempt at comparing some results obtained via a CFD-based RANS solver and the slender body theory for critical outer flow in a dredged channel.

The numerical simulation of ship flows has evolved into a highly practical approach in naval architecture. In typical virtual towing tanks, the principle of Galilean relativity is invoked to maintain the ship as fixed, while the surrounding water is prescribed to flow past it. This assumption may be identified, at least partly, as being responsible for the wide-scale adoption of computational solutions within practitioners&rsquo, toolkits. However, it carries several assumptions, such as the levels of inlet turbulence and their effect on flow properties. This study presents an alternative virtual towing tank, where the ship is simulated to advance over a stationary fluid. To supplement the present work, the free surface disturbance is processed into Fourier space to determine the Kelvin half-angle for an example case. The results suggest that it is possible to construct a fully unsteady virtual towing tank using the overset method, without relying on Galilean relativity. Differences between theoretical and numerical predictions for the Kelvin half-angle are predominantly attributed to the assumptions used by the theoretical method. The methods presented in this work can potentially be used to validate free-surface flows, even when one does not have access to experimental wave elevation data.

Historically, the prediction ship resistance has received its fair share of attention by the scientific community. Yet, a robust scaling law still lacks, leaving testing facilities to rely on experience-based approaches and large datasets accumulated from years of operation. Academia's concern regarding this has not led to an extrapolation procedure, capable of bearing scrutiny adequately. One way to circumvent what has become the bane of the study of ship resistance is to perform Reynolds averaged Navier–Stokes (RANS) simulations directly in full-scale. The rapid advent of such methods has meant that confidence levels in predictions achieved by RANS simulations are low. This paper explores and demonstrates scale effects on the constituent components of ship resistance by performing a geosim analysis using a Computational Fluid Dynamics approach. Emphasis is placed on challenging the assumptions imposed as part of the currently accepted ship resistance extrapolation procedure. Our results suggest that a high degree of uncertainty exists in the calculated full-scale resistance depending on the approach taken towards its evaluation. In particular, scale effects are demonstrated in wave resistance, while free surface effects are palpable in the frictional resistance.