A state-of-the-art review is presented of mathematical manoeuvring models for surface ships and parameter estimation methods that have been used to build mathematical manoeuvring models for surface ships. In the first part, the classical manoeuvring models, such as the Abkowitz model, MMG, Nomoto and their revised versions, are revisited and the model structure with the hydrodynamic coefficients is also presented. Then, manoeuvring tests, including both the scaled model tests and sea trials, are introduced with the fact that the test data is critically important to obtain reliable results using parameter estimation methods. In the last part, selected papers published in journals and international conferences are reviewed and the statistical analysis of the manoeuvring models, test data, system identification methods and environmental disturbances used in the paper is presented.

Flow characteristics around a wall-mounted square cylinder have been numerically simulated at aspect ratios (AR) ranging from 4 to 7 at Re = 10 000. Four turbulence models have been compared in terms of drag coefficient (C_D). The closest result has been provided by two turbulence models, namely, k − ε Realizable and k − ω Shear Stress Transport (SST). Hence, these models were utilized to present the flow patterns of pressure distributions, turbulent kinetic energy values, velocity magnitude values with streamlines, streamwise velocity components, cross-stream velocity components and spanwise velocity components on different planes. Flow stagnation has been attained in front of the cylinder. Pressure values peaked for the upstream region. Over the cylinders, the tip vortex structure was dominant owing to the influence of the free end. Flow separation from the top front edge of the body has been obtained. The dividing streamline affected by the flow separation was highly effective in the wake region and moved nearer to the body when the aspect ratio was decreased; the reason was the wake shrinkage owing to the decreasing aspect ratio. Upwash and downwash have been seen in the cylinder wake. These two models presented similar flow patterns and drag coefficients. These drag coefficients are in good agreement with those in previous studies.

In designing modern vessels, calculating the propulsion performance of ships in ice is important, including propeller effective thrust, number of revolutions, consumed power, and ship speed. Such calculations allow for more accurate prediction of the ice performance of a designed ship and provide inputs for designers of ship power and automation systems. Preliminary calculations of ship propulsion and thrust characteristics in ice can enable predictions of full-scale ice resistance without measuring the propeller thrust during sea trials. Measuring propeller revolutions, ship speed, and the power delivered to propellers could be sufficient to determine the propeller thrust of the vessel. At present, significant difficulties arise in determining the thrust of icebreakers and ice-class ships in ice conditions. These challenges are related to the fact that the traditional system of propeller/hull interaction coefficients does not function correctly in ice conditions. The wake fraction becomes negative and tends to minus infinity starting from a certain value of the propeller advance coefficient. This issue prevents accurate determination of the performance characteristics, thrust, and rotational speed of the propulsors. In this study, an alternative system of propeller/hull interaction coefficients for ice is proposed. It enables the calculation of all propulsion parameters in ice based on standard hydrodynamic tests with self-propulsion models. An experimental method is developed to determine alternative propeller/hull interaction coefficients. A prediction method is suggested to determine propulsion performance in ice based on the alternative interaction coefficient system. A case study applying the propulsion prediction method for ice conditions is provided. This study also discusses the following issues of ship operation in ice: the scale effect of icebreaker propellers and the prospects for introducing an ice interaction coefficient.

The water curtain spray system of the ship helps reduce surface thermal load and lowers thermal infrared radiation, notably enhancing the stealth and survivability of naval ships. The performance of the water curtain spray system is largely influenced by the density of the nozzles and their installation height. Therefore, a test platform was established to investigate these critical influencing factors, employing an orthogonal design methodology for the experimental study. Specifically, the study evaluated the effects of varying distances to the steel plate target and different injection heights on the cooling performance of the system. Results demonstrate that using one nozzle per 4 square meters of the ship’s surface area effectively lowers the surface temperature, bringing it closer to the ambient background temperature. This nozzle configuration creates irregular infrared heat patterns, which complicate the task for infrared detectors to discern the ship’s outline, thus enhancing its infrared stealth. Additionally, maintaining the nozzle installation height within 0.6 m to prevent the temperature difference between the steel plate and the background temperature from exceeding 4 K. Moreover, as the infrared imaging distance increases from 3 to 9 m, the temperature difference measured by the thermocouple and the infrared imager increases by 141.27%. Furthermore, with the increase in infrared imaging distance, the infrared temperature of the target steel plate approaches the background temperature, indicating improved detectability. These findings have significantly enhanced the stealth capabilities of naval ships, maximizing their immunity to infrared-guided weapon attacks. Moreover, their importance in improving the survivability of ships on the water surface cannot be underestimated.

A numerical simulation analysis is conducted to examine the unsteady hydrodynamic characteristics of vortex-induced vibration (VIV) and the suppression effect of helical strakes on VIV in subsea pipelines. The analysis uses the standard k − ε turbulence model for 4.5- and 12.75-inch pipes, and its accuracy is verified by comparing the results with large-scale hydrodynamic experiments. These experiments are designed to evaluate the suppression efficiency of VIV with and without helical strakes, focusing on displacement and drag coefficients under different flow conditions. Furthermore, the influence of important geometric parameters of the helical strakes on drag coefficients and VIV suppression efficiency at different flow rates is compared and discussed. Numerical results agree well with experimental data for drag coefficient and vortex-shedding frequency. Spring-pipe self-excited vibration experimental tests reveal that the installation of helical strakes substantially reduces the drag coefficient of VIV within a certain flow rate range, achieving suppression efficiencies exceeding 90% with strake heights larger than 0.15D. Notably, the optimized parameter combination of helical strakes, with a pitch of 15D, a fin height of 0.2D, and 45° edge slopes, maintains high suppression efficiency, thereby exhibiting superior performance. This study provides a valuable reference for the design and application of helical strakes and VIV suppression in subsea engineering.

Biodiesel is a clean and renewable energy, and it is an effective measure to optimize engine combustion fueled with biodiesel to meet the increasingly strict toxic and CO₂ emission regulations of internal combustion engines. A suitable-scale chemical kinetic mechanism is very crucial for the accurate and rapid prediction of engine combustion and emissions. However, most previous researchers developed the mechanism of blend fuels through the separate simplification and merging of the reduced mechanisms of diesel and biodiesel rather than considering their cross-reaction. In this study, a new reduced chemical reaction kinetics mechanism of diesel and biodiesel was constructed through the adoption of directed relationship graph (DRG), directed relationship graph with error propagation, and full-species sensitivity analysis (FSSA). N-heptane and methyl decanoate (MD) were selected as surrogates of traditional diesel and biodiesel, respectively. In this mechanism, the interactions between the intermediate products of both fuels were considered based on the cross-reaction theory. Reaction pathways were revealed, and the key species involved in the oxidation of n-heptane and MD were identified through sensitivity analyses. The reduced mechanism of n-heptane/MD consisting of 288 species and 800 reactions was developed and sufficiently verified by published experimental data. Prediction maps of ignition delay time were established at a wide range of parameter matrices (temperature from 600 to 1 700 K, pressure from 10 bar to 80 bar, equivalence ratio from 0.5 to 1.5) and different substitution ratios to identify the occurrence regions of the cross-reaction. Concentration and sensitivity analyses were then conducted to further investigate the effects of cross-reactions. The results indicate temperature as the primary factor causing cross-reactivity. In addition, the reduced mechanism with cross-reactions was more accurate than that without cross-reactions. At 700–1 000 K, the cross-reactions inhibited the consumption of n-heptane/MD, which resulted in a prolonged ignition delay time. At this point, the elementary reaction, NC₇H₁₆+OH<=>C₇H₁₅-2+H₂O, played a dominant role in fuel consumption. Specifically, the contribution of the MD consumption reaction to ignition decreased, and the increased generation time of OH, HO₂, and H₂O₂ was directly responsible for the increased ignition delay.