The sensitivity of moving particle semi-implicit (MPS) simulations to numerical parameters is investigated in this study. Although the verification and validation (V&V) are important to ensure accurate numerical results, the MPS has poor performance in convergences with a time step size. Therefore, users of the MPS need to tune numerical parameters to fit results into benchmarks. However, such tuning parameters are not always valid for other simulations. We propose a practical numerical condition for the MPS simulation of a two-dimensional wedge slamming problem (i.e., an MPS-slamming condition). The MPS-slamming condition is represented by an MPS-slamming number, which provides the optimum time step size once the MPS-slamming number, slamming velocity, deadrise angle of the wedge, and particle size are decided. The simulation study shows that the MPS results can be characterized by the proposed MPS-slamming condition, and the use of the same MPS-slamming number provides a similar flow.

This paper discusses mathematical modeling of a ship equipped with energy-saving wing devices. Therewith, the ship is mathematically represented by an elongated hull with high-aspect-ratio wings mounted near its bow and stern. Equations, describing ship motions in regular oncoming waves, are written in the spirit of strip theory with account of inertial and damping influence of energy-saving wing elements with the use of linear expansion of wing-related forces with respect to heave and pitch perturbations. This approach readily yields fast numerical solutions for the propulsion of a ship with wings in waves. The latter solutions are then used as an input for calculation of thrust on wing elements on the basis of classical unsteady foil theories corrected for finite aspect ratio. To evaluate speed of the ship in the modes which allow cruising exclusively by wave power, it is hypothetically assumed that in this case, the wave-generated thrust on the wings equals total drag of the ship-plus-wings system, the latter being defined as a sum of its viscous, wave-making, induced (for wing elements) and added-wave components. Excepting the added-wave term and wings’ contributions, the total drag is calculated herein by Holtrop method whereas added-wave resistance is evaluated with Beukelman-Gerritsma formula involving kinematic parameters of heaving and pitching motions of the ship calculated both without and with account of the wings. Also discussed in the paper is a decrease of added wave resistance for a ship with wings as compared to that of ship without wings. Finally, the energy efficiency design index (EEDI) introduced by the International Maritime Organization (IMO) is discussed for representative sea conditions as a measure of ship environmental friendliness.

In many cases of wave structure interactions, three-dimensional models are used to demonstrate real-life complex environments in large domain scales. In the seakeeping context, predicting the motion responses in the interaction of a long body resembling a ship structure with regular waves is crucial and can be challenging. In this work, regular waves interacting with a rigid floating structure were simulated using the open-source code based on the weakly compressible smoothed particle hydrodynamics (WCSPH) method, and optimal parameters were suggested for different wave environments. Vertical displacements were computed, and their response amplitude operators (RAOs) were found to be in good agreement with experimental, numerical, and analytical results. Discrepancies of numerical and experimental RAOs tended to increase at low wave frequencies, particularly at amidships and near the bow. In addition, the instantaneous wave contours of the surrounding model were examined to reveal the effects of localized waves along the structure and wave dissipation. The results indicated that the motion response from the WCSPH responds well at the highest frequency range (ω > 5.235 rad/s).

This paper is concerned with the generation of gravity waves due to prescribed initial axisymmetric disturbances created at the surface of an ice sheet covering the ocean with a porous bottom. The ice cover is modeled as a thin elastic plate, and the bottom porosity is described by a real parameter. Using linear theory, the problem is formulated as an initial value problem for the velocity potential describing the motion. In the mathematical analysis, the Laplace and Hankel transform techniques have been used to obtain the depression of the ice-covered surface in the form of a multiple infinite integral. This integral is evaluated asymptotically by the method of stationary phase twice for a long time and a large distance from the origin. Simple numerical computations are performed to illustrate the effect of the ice-covered surface and bottom porosity on the surface elevation, phase velocity, and group velocity of the surface gravity waves. Mainly the far-field behavior of the progressive waves is observed in two different cases, namely initial depression and an impulse concentrated at the origin. From graphical representations, it is clearly visible that the presence of ice cover and a porous bottom decreases the wave amplitude. Due to the porous bottom, the amplitude of phase velocity decreases, whereas the amplitude of group velocity increases.

A small waterplane area twin hull (SWATH) has excellent seakeeping performance and low wave-making resistance, and it has been applied to small working craft, pleasure boats, and unmanned surface vehicles. However, with the increase in speed, the hydrodynamic resistance of SWATH will increase exponentially because of its large wet surface, followed by the uncomfortable situation of the hull underwater part relative to the water level and in terms of high trim by stern and high sinkage. A way to improve this situation is to reduce the depth of the draft at high speeds to ensure that all or a part of the volume of the submerged bodies is above the water level. Based on this idea, a new type of semi-SWATH hull form was analyzed in this paper. The two submerged bodies of the SWATH have a catamaran boat shape. This paper employed Siemens PLM Star-CCM+ to study the hydrodynamic performance of an advanced semi-SWATH model. Bare-hull resistance was estimated for both SWATH and CAT (CATAMARAN) modes in calm water. Moreover, the effect of fixed stabilizing fins with different angles on the vertical motions of the vessel in regular head waves was investigated with an overset mesh approach. The vertical motion responses were estimated at different wave encounter frequencies, and the present numerical method results have been verified by already published experimental data.

Complementarities between wind and wave energies have many significant advantages that are unavailable with the sole deployment of either. Using all available wind speed, significant wave height, and wave period buoy observations over a 10-year period (i.e., 2009–2019), colocated wind and wave energy resources are estimated. Although buoy records are imperfect, results show that the inner Caribbean Sea (CS) under the influence of the Caribbean low-level jet has the highest wind energy resource at ~ 1500 W/m², followed by the outer CS at ~ 600 W/m² and Atlantic Ocean (AO) at ~ 550–600 W/m² at a 100 m height. Wave energy was most abundant in the AO at 14 kW/m, followed by the inner CS at 13 kW/m and outer CS at 5 kW/m. The average and dominant wave energies can reach a maximum of 10 and 14 kW/m, respectively. Asymmetry between wind and wave energy resources is observed in the AO, where wave energy is higher than the low wind speed/energy would suggest. Swell is responsible for this discrepancy; thus, it must be considered not only for wave energy extraction but also for wind turbine fatigue, stability, and power extraction efficiency.

This paper described the process of generating the optimal parametric hull shape with a fully parametric modeling method for three containerships of different sizes. The newly created parametric ship hull was applied to another ship with a similar shape, which greatly saved time cost. A process of selecting design variables was developed, and during this process, the influence of these variables on calm water resistance was analyzed. After we obtained the optimal hulls, the wave added resistance and motions of original hulls and optimal hulls in regular head waves were analyzed and compared with experimental results. Computations of the flow around the hulls were obtained from a validated nonlinear potential flow boundary element method. Using the multi-objective optimization algorithm, surrogate-based global optimization (SBGO) reduced the computational effort. Compared with the original hull, wave resistance of the optimal hulls was significantly reduced for the two larger ships at Froude numbers corresponding to their design speeds. Optimizing the hull of the containerships slightly reduced their wave added resistance and total resistance in regular head waves, while optimization of their hulls hardly affected wave-induced motions.

This work explores the postbuckling behavior of a marine stiffened composite plate in the presence of initial imperfections. The imperfection shapes are derived from buckling mode shapes and their combinations. Thereafter, these imperfection shapes are applied to the model, and nonlinear large deflection finite element and progressive failure analyses are performed in ANSYS 18.2 software. The Hashin failure criterion is employed to model the progressive failure in the stiffened composite plate. The effect of the initial geometric imperfection on the stiffened composite plate is investigated by considering various imperfection patterns and magnitudes. Results show that when the magnitude of the imperfection is 20 mm, the ultimate strength of the stiffened composite plate decreases by 31%. Moreover, global imperfection shapes are found to be fundamental in determining the ultimate strength of stiffened composite plates and their postbuckling.

Blast pressure measurements of a controlled underwater explosion in the sea were carried out. An explosive of 25-kg trinitrotoluene (TNT) equivalent was detonated, and the blast pressures were recorded by eight different high-performance pressure sensors that work at the nonresonant high-voltage output in adverse underwater conditions. Recorded peak pressure values are used to establish a relationship in the well-known form of empirical underwater explosion (UNDEX) loading formula. Constants of the formula are redetermined by employing the least-squares method in two different forms for best fitting to the measured data. The newly determined constants are found to be only slightly different from the generally accepted ones.

In this paper, the flow physics and impact dynamics of a sphere bouncing on a water surface are studied experimentally. During the experiments, high-speed camera photography techniques are used to capture the cavity and free surface evolution when the sphere impacts and skips on the water surface. The influences of the impact velocity (v₁) and impact angle (θ₁) of the sphere on the bouncing flow physics are also investigated, including the cavitation evolution, motion characteristics, and bounding law. Regulations for the relationship between v₁ and θ₁ to judge whether the sphere can bounce on the water surface are presented and analyzed by summarizing a large amount of experimental data. In addition, the effect of θ₁ on the energy loss of the sphere is also analyzed and discussed. The experiment results show that there is a fitted curve of v₁ = 17.5θ₁ ? 45.5 determining the relationship between the critical initial velocity and angle whether the sphere bounces on the water surface.

Searching for the optimal cabin layout plan is an effective way to improve the efficiency of the overall design and reduce a ship’s operation costs. The multitasking states of a ship involve several statuses when facing different missions during a voyage, such as the status of the marine supply and emergency escape. The human flow and logistics between cabins will change as the state changes. An ideal cabin layout plan, which is directly impacted by the above-mentioned factors, can meet the different requirements of several statuses to a higher degree. Inevitable deviations exist in the quantification of human flow and logistics. Moreover, uncontrollability is present in the flow situation during actual operations. The coupling of these deviations and uncontrollability shows typical uncertainties, which must be considered in the design process. Thus, it is important to integrate the demands of the human flow and logistics in multiple states into an uncertainty parameter scheme. This research considers the uncertainties of adjacent and circulating strengths obtained after quantifying the human flow and logistics. Interval numbers are used to integrate them, a two-layer nested system of interval optimization is introduced, and different optimization algorithms are substituted for solving calculations. The comparison and analysis of the calculation results with deterministic optimization show that the conclusions obtained can provide feasible guidance for cabin layout scheme.

Caisson breakwaters are mainly constructed in deep waters to protect an area against waves. These breakwaters are conventionally designed based on the concept of the safety factor. However, the wave loads and resistance of structures have epistemic or aleatory uncertainties. Furthermore, sliding failure is one of the most important failure modes of caisson breakwaters. In most previous studies, for assessment purposes, uncertainties, such as wave and wave period variation, were ignored. Therefore, in this study, Bayesian reliability analysis is implemented to assess the failure probability of the sliding of Tombak port breakwater in the Persian Gulf. The mean and standard deviations were taken as random variables to consider dismissed uncertainties. For this purpose, the first-order reliability method (FORM) and the first principal curvature correction in FORM are used to calculate the reliability index. The performances of these methods are verified by importance sampling through Monte Carlo simulation (MCS). In addition, the reliability index sensitivities of each random variable are calculated to evaluate the importance of different random variables while calculating the caisson sliding. The results show that the reliability index is most sensitive to the coefficients of friction, wave height, and caisson weight (or concrete density). The sensitivity of the failure probability of each of the random variables and their uncertainties are calculated by the derivative method. Finally, the Bayesian regression is implemented to predict the statistical properties of breakwater sliding with non-informative priors, which are compared to Goda’s formulation, used in breakwater design standards. The analysis shows that the model posterior for the sliding of a caisson breakwater has a mean and standard deviation of 0.039 and 0.022, respectively. A normal quantile analysis and residual analysis are also performed to evaluate the correctness of the model responses.

The mooring and riser system is the most critical part of an offshore oil terminal. Traditionally, these two parts are designed separately without considering the nonlinear interaction between them. Thus, the present paper aims to develop an integrated design process for riser systems with a lazy-S configuration and mooring systems in the offshore catenary anchor leg mooring (CALM) oil terminal. One of the important criteria considered in this integrated design is the offset diagram and safe operation zone (SAFOP) related to the mooring system and the riser, respectively. These two diagrams are obtained separately by different analyses; therefore, codes or standards are available separately for two components. In this methodology, the diagrams of both risers and mooring lines are incorporated into a single spiral, thus identifying the safe and failure zones of risers and the mooring lines of the oil terminal. This, in turn, leads to substantial benefits in terms of overall system response, cost reduction, and safety to the offshore oil terminal. To implement this process, three different riser lengths with the lazy-S configuration are considered at three different sea depths at the terminal installation site. For each condition, the integrated design of the mooring system and riser is executed according to the derived procedure. Then, coupled dynamic models, wherein both buoys and hoses are included, are developed using OrcaFlex. Results show that the criteria of the relevant regulations are not satisfied by reducing the length of the riser relative to the designed size. Further, as water depth increases, this type of riser configuration shows good coupled performance while interacting with the mooring system. In the cross offset mode, the maximum margin is created between the offset diagram and the SAFOP diagram, while the most critical dynamic response of the tanker and terminal system occurs in the near and far modes. Therefore, with this method, the best position for the riser direction with the tanker direction is 90° in the best case.

The latching control represents an attractive alternative to increase the power absorption of wave energy converters (WECs) by tuning the phase of oscillator velocity to the wave excitation phase. However, increasing the amplitude of motion of the floating body is not the only challenge to obtain a good performance of the WEC. It also depends on the efficiency of the power take-off system (PTO). This study aims to address the actual power performance and operation of a heaving point absorber with a direct mechanical drive PTO system controlled by latching. The PTO characteristics, such as the gear ratio, the flywheel inertia, and the electric generator, are analyzed in the WEC performance. Three cylindrical point absorbers are also considered in the present study. A wave-to-wire model is developed to simulate the coupled hydro-electro-mechanical system in regular waves. The wave energy converter (WEC) performance is analyzed using the potential linear theory but considering the viscous damping effect according to the Morison equation to avoid the overestimated responses of the linear theory near resonance when the latching control system is applied. The latching control system increases the mean power. However, the increase is not significant if the parameters that characterize the WEC provide a considerable mean power. The performance of the proposed mechanical power take-off depends on the gear ratio and flywheel. However, the gear ratio shows a more significant influence than the flywheel inertia. The operating range of the generator and the diameter/draft ratio of the buoy also influence the PTO performance.