Inland water vessels are impacted by climate change in two respects. First of all, they will need to convert to low-impact power propulsion and energy (PPE) systems. Secondly, they will need to deal with the impact of climate change, especially longer periods of very low and high water. This paper reviews the multi facet impacts of climate change on inland waterway vessel performance and problems associated with the choice of alternative power energy and propulsion (PPE) system on the vessel’s performance.@en

The paper presents velocity measurements, using particle image velocimetry, as well as a reconstruction of hydrodynamic pressures for the analysis of fast ships. Stereoscopic PIV measurements with a towed underwater PIV system are conducted during towing tank tests to obtain the velocity field in the bow region of a fast ship at speeds up to Fr=0.8. While the model is kept at a fixed trim and sinkage, multi-plane PIV measurements with a total of 68 measurement planes are conducted to reconstruct a volumetric representation of the time-averaged velocity field in the bow region. The obtained velocity field is subsequently used for a volumetric description of the time-averaged hydrodynamic pressure field. In addition to these captive runs, forced oscillation tests are conducted. During these tests, the flow field is recorded in three successive planes to obtain a local phase-averaged description of the velocity and its gradients for the reconstruction of the phase-averaged hydrodynamic pressure field. The postprocessing procedure for the pressure reconstruction, including the solution of the Poisson equation, is implemented into the open-source CFD package OpenFOAM. For the detection of the free surface and the ship hull, an automated procedure is presented. Experimental results are finally compared to results from numerical simulations. Results show that the PIV method is capable of capturing the flow characteristics in the bow region of a fast ship. In addition, it can be used together with the pressure Poisson equation to obtain the hydrodynamic pressure field. However, large out-of-plane velocities require a large dynamic range, which limits the resolution of local effects close to the ship hull.

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The conventional extrapolation of ship resistance from model tests to full scale presumes that the coefficient of wave-making resistance (C_w) depends on the Froude number only. This leads to the assumption that C_w of a ship is identical to C_w of its scaled model. However, this assumption is challenged in shallow water due to viscous effects, which are represented by the Reynolds number (Re). In this study, different scales (different Re) of the Wigley hull and the KCS hull are used to investigate the scale effects on C_w numerically. After verification and validation, systematic computations are performed for both ships and their scaled models in various shallow-water conditions. Based on the results, significantly larger values of C_w are found for the KCS at model scale in very shallow water, suggesting that the conventional extrapolation has to be reconsidered. Additionally, this study reveals the relationship between the changes in frictional resistance coefficient (C_f) and the changes in C_w caused by shallow water, which benefits the prediction of shallow water effects on C_w. Finally, use of a larger ship model, where the Re is also higher, is recommended for resistance tests in shallow water to reduce scale effects on C_w.

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In ship model tests, a model-ship correlation line (e.g., the ITTC57 formula) is used to calculate the frictional resistance of both the ship and its scaled model. However, this line is designed for deep water and the effects of water depth is not considered. Research has been conducted to improve the correlation line in shallow water, but studies of the extremely shallow water case (depth/draft, h/T < 1.2) are rare. This study focuses on the friction of two ship types in extremely shallow water, where the ship’s boundary layer cannot develop freely. The physical details are analyzed based on the data generated with Computational Fluid Dynamics (CFD) calculations. The results show that for certain ship types at the same Reynolds number, the frictional resistance becomes smaller when the water is shallower. The geometry of the ship, in addition to the Reynolds number, becomes essential to the prediction of ship’s friction in extremely shallow water. Therefore, this scenario is different from intermediate shallow and deep water, and the prediction method should be considered separately. The data and analysis shown in this study can help to improve the understanding and prediction of ship’s frictional resistance in extremely shallow water.@en

Understanding the characteristics of the waves generated by a ship can improve the prediction of ship’s wave resistance. Such waves generated in deep water have been studied in detail whereas in shallow water, the existing methods, mostly derived from inviscid flow, are not fully coping with physical phenomena. In this study, the changes in the height and length of ship-generated waves in shallow water are explored as well as the effects of waterbed friction. A Computational Fluid Dynamics (CFD) approach is selected as the main tool and a Wigley hull is chosen due to the availability of validating data. It is found that the wave cut analysis will slightly underestimate the wave resistance. The effects of bottom friction are perceivable and should be considered if a highly accurate prediction is required. This study, which improves the understanding of ship-generated waves, is expected to contribute to the prediction of ship’s wave resistance in shallow water.@en

Accurate resistance prediction for ships sailing in vertically restricted waterways is highly required to improve the design and operation for large ships entering harbors and for vessels navigating in inland waters. The methods derived from deep water may lead to large errors, and studies considering shallow water effects are needed. As most ships sailing in shallow water operate at a low Froude number, the viscous resistance dominates the total resistance and becomes the main concern. In this study, a Wigley hull and the KCS (KRISO Container Ship), which have available benchmark data, are applied. A typical 86 m long inland ship is then chosen to further investigate the influence of a different hull form. Results show that the friction and the viscous pressure resistance depend on ship types, speeds, and water depths. A formula to predict a ship's friction in shallow water is given with some constants determined based on ship's characteristics. A form factor defined based on computed ship's friction is suggested, and an empirical expression is provided for each ship applied. With the investigations for three ship forms, this study is expected to provide inspirations to further improve the prediction of ship's viscous resistance in shallow water.@en

The present study describes the application of the particle image velocimetry (PIV) technique for the reconstruction of hydrodynamic pressures and loads on a ship model from measured velocity fields during towing tank tests. As an alternative to conventional pressure and force measurement techniques the method simultaneously pictures the velocity field and captures the dynamic aspect of the flow. The presented measurements are conducted in the transom region of a generic hull of a planing vessel which is equipped with an interceptor to create a stagnating flow, associated with a high pressure peak. The flow close to the hull is captured with an underwater stereoscopic PIV system and the pressure peak in front of the interceptor is reconstructed from time-averaged velocity fields. Results show the effect of different interceptor heights on the pressure distribution in the center-plane of the model. Further, a 3D flow field is reconstructed from scanning PIV measurements to analyze the lift reduction due to the finite span of the interceptor. The spatial variation of the measurement uncertainty is analyzed and propagated to the pressure field uncertainty and the potential of the method is further evaluated by comparison with numerical results from steady Reynolds Averaged Navier-Stokes (RANS) simulations.

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The ITTC57 correlation line, which is derived based on the assumption that the water in which ships advance is infinite deep and wide. However, for ships sailing in the waterway with limited water depth, the frictional resistance will be influenced leading to a decreasing accuracy of the prediction with this correlation line. In this study, a modification of the ITTC57 correlation line is proposed to correct the effects in very shallow water specifically for the flat area of the bottom of the ship. Under some assumptions, this area can be simplified to a 2D flat plate with a parallel wall close to it to study how the shallow water conditions of two interacting boundary conditions are affecting the flat plate friction coefficient. Computational fluid dynamics (CFD) calculations are applied to investigate how a friction line specifically in shallow water deviates from the conventional lines. Such deviations may severely affect the extrapolation of a ship model’s resistance to full scale and, therefore, the accuracy of ship’s performance prediction. Cases at ten Reynolds numbers from 10⁵ to 10⁹ are simulated on the 2D flat plate. Seven different distances between the flat plate and the parallel wall were chosen to generate various shallow water conditions, and consequently, a database including frictional resistance coefficients, Reynolds numbers and the distance between those two walls is built. Results indicate that thinner boundary layers are observed in shallow water conditions, and the scale effects which has a significant impact on resistance extrapolation are also observed. Furthermore, the assumption of the zero pressure gradients (ZPG) which is commonly used in deep water is no longer valid in extremely shallow ones. Finally, a modification for the ITTC57 correlations line considering shallow water effects is proposed, which is willing to improve the prediction of the frictional resistance of those ships with a large area of flat bottom and sail in shallow water.

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CFD (Computational Fluid Dynamics) calculations have been making dramatic contributions to ship resistance prediction. Since the virtual models used are always simplifications of the real ships and fluid, results need to be validated by experiments. However, although a certain number of model tests can be found, the publicly available resistance tests in shallow to extremely shallow water (water depth-to-draft ratio h/T ≤ 2.0) are rare. Therefore, to provide data for validation, a test of an inland ship model in shallow water is performed in a towing tank. Four shallow water depths are applied and one deep water case is added for comparison. The uncertainties in this test are analyzed for the measuring instruments as well as the resistance, trim and sinkage. This test is motivated to provide the path for the ongoing research by the authors on the improved prediction of ship resistance in shallow water and enables the benchmark for other researchers, who investigate ship resistance in extremely shallow water, with experimental data to validate CFD calculations@en

Inland vessels generally experience a resistance increment when the water in which they sail is extremely shallow. In this case, resistance extrapolation from ship model to full scale becomes complicated, and the traditional approaches do not often lead to satisfactory predictions. In this study, both numerical and experimental methods were applied to investigate the ship resistance, trim and sinkage in extremely shallow water. In the numerical calculations, the model initially has a trim and sinkage obtained from the model tests. The overset mesh technique was used to save the meshing effort. A 1/30 scaled model, which is only allowed to pitch and heave, was used in the model tests. It was found that, in extremely shallow water, the ITTC57 correlation line is not sufficient to extrapolate the resistance.@en

The particle image velocimetry (PIV) technique has become a reliable method for capturing the velocity field and its derivatives, even in complex flows and is now also widely used for validation of numerical codes. As the imaging system is sensitive to vibrations, the application in environments such as towing tanks makes it a challenging task. Especially when operating the towing tank carriage at higher speeds structural vibrations increase significantly. However, to apply this technique for the analysis of planing and semi-planing vessels, this is absolutely necessary. To assess the ability of a PIV system to capture the flow features close to a ship model while being towed at high speeds, a stereo PIV system was installed in the TU Delft towing tank. Measurements are conducted in the transom region of a generic high-speed vessel hull with a flat bottomed aft section, which is equipped with an interceptor at the transom. It is shown that with increasing carriage speed, vibrations of the imaging system increase, which ultimately can affect the quality of PIV recordings. The effect of vibrations is quantified by analysis of successive recordings and based on this, a shift correction is applied. A comparison with numerical results shows that the flow around the interceptor is well captured by the PIV system@en

This paper presents the span from the historical roots and background of air lubrication to actual research project results derived from full-scale demonstrators or as expected from the EcoLiner currently being under construction. Three techniques are discussed: Air Cavity Ships, Air-film and (micro-)bubble drag reduction. @en