Combat Ship Research Articles

Experimental and computational study of aerodynamic loads on the NATO Generic Destroyer

This paper describes a detailed study into the aerodynamic loading of a 150 m long conceptual combat ship known as the NATO Generic Destroyer. Results are presented from a wind tunnel experiment in which the drag and side forces, and the roll and yaw moments, were measured around the 360° azimuth using a 0.75 m long model of the ship. Surface pressures were also measured between 0° and 180°, using 252 pressure taps distributed over the surface of the ship. The measured loads and surface pressures are shown to agree reasonably well, for most wind directions, with those predicted by a steady RANS CFD method. An unexpected result was found in the drag measurements, whereby the force was found to be towards the stern for wind directions up to 120°, i.e., with a wind component towards the bow. The reason for this apparent anomaly was explained by considering the flow field and the surface pressures acting on the ship for wind angles between 90° and 135°. The primary purpose of the paper is to make available a set of high-quality aerodynamic load measurements for a well-defined ship geometry, which is freely accessible, thereby providing a test case for CFD validation.

The Importance of Ontological Commitment and Linguistics in Relation to the Elucidation of Design Requirements

One of the design process’s earliest and most critical stages is establishing and determining requirements. Design requirements are often expressed through language, whether in written documents, diagrams, or verbal discussions in terms of the client’s “wants” and “needs” or balancing what they can “afford.” Designers use of quotes around “wants,” “needs,” and “afford” signals ambiguity or doubt in the meaning of the terms. The language used during early discourse is crucial for expressing and translating theseambiguous terms into specific unambiguous design requirements, which significantly shape and constrain possible solutions. In philosophy, this concept is known as ontological commitment. Embedded language in requirements documents, expressed through constraints, objectives, and functions, establish the ontological commitment to a specific solution space. Prior marine design research has focused on the wicked problem of requirements elucidation, with the goal visualizing potential solutions derived from language, and a more direct link to ontological commitment was developed by Andrews in the concept of style Duchateau (2016) van Ores (2011) Andrews (2012). However, the role and impact of linguistics in translating and interpreting uncertain or ambiguous terms into specific design requirements has been largely overlooked. This paper presents modern direct examples of ontological commitment from requirements development for the Littoral Combat Ship.

Comparative Investigation of Resistance Prediction for Surface Combatant Ship Model using CFD Modeling

The Multi-Mission Surface Combatant (MMSC) is a highly maneuverable combatant ship capable of littoral and open ocean operations. It was designed to confront modern maritime and economic security threats. The MMSC takes the proven capabilities of the littoral combat ship and the inherent flexibility of the Freedom-variant hull to meet the unique maritime requirements of international navies. Computational fluid dynamics (CFD) is applied to present a method to predict the resistance for new surface combatant ship. First, calculations for a typical benchmark DTMB 5415-24 model are carried out using three different mesh sizes for Froude numbers from 0.10 to 0.48 for the purpose of model validation by Star CCM+. The numerical results are compared with the experimental data and the published CFD solutions in terms of wave field and resistance coefficients for accuracy of the solution parameters. Finally, the method is used to study the influence of Froude number variation on the total resistance and wave pattern for the new combatant ship model under the same conditions. Quantitative agreement between the numerical simulations has been observed. This demonstrates that our CFD model is capable of simulating the steady flow around a ship hull with an acceptable accuracy and thus can be used as a complementary tool to laboratory model tests for ship design and ship hydrodynamic research.

Sensor deviation anomaly trend prediction based on phase space reconstruction and Support Vector Regression

Ship combat systems are developing in the direction of integration and intelligence, and the integration also brings problems such as difficulty in predicting abnormal sensor trends in combat systems. The failure characteristics of sensors in combat systems are highly secretive, and it is difficult to detect and deal with system equipment failures by relying on empirical qualitative or single-indicator testing methods. In order to safeguard the ship’s combat capability and make reasonable maintenance decisions, it is important to study more accurate prediction methods. This article proposes a method for predicting sensor deviation anomaly trends based on phase space reconstruction and Support Vector Regression(SVR), taking sensors in naval combat systems as typical research objects. Firstly, a phase space reconstruction is performed on the sensor deviation time series data to increase the accuracy of subsequent prediction; then a SVR prediction model is built, and the model is trained and optimised using the reconstructed data; finally, the constructed prediction model is compared with the regular SVR model and BP neural network model to verify that the constructed model has higher prediction accuracy.

The NATO generic destroyer – a shared geometry for collaborative research into modelling and simulation of shipboard helicopter launch and recovery

The helicopter-ship dynamic interface is the environment above the landing deck of a ship where a helicopter pilot has to control the aircraft while contending with a moving deck and an unsteady airflow known as the ship airwake. Research into understanding this environment has included modelling the airwake using wind tunnel studies and Computational Fluid Dynamics, and has often used the Simple Frigate Shape (SFS), a generic ship geometry representative of a naval frigate. This paper reviews the contribution that the SFS has made to research into the helicopter-ship dynamic interface, and introduces a new ship geometry for future research. The new ship, developed within a NATO Research Task Group, is the NATO Generic Destroyer (NATO-GD), a concept ship with a simplified geometry that is more representative of a modern helicopter-enabled combat ship with a stealthy superstructure. As well as introducing the NATO-GD as a common platform for research, the paper also introduces a number of ship motion profiles to encourage new research that will include the effect of ship motion on the airwake. It is anticipated that future research on a common ship, with prescribed motion and adopting a common helicopter will lead to improved or new modelling methodologies.

Effects of Hook, Interceptor, and Water Jets on LCS Resistance/Power, Sinkage, and Trim

Verification and validation of computational fluid dynamic simulations are performed at model and full scales for the high-speed littoral combat ship (LCS) surface combatant, including the effects of hook, interceptors, and water-jet propulsion. Predictions of the body force thrust, sinkage, and trim use a speed controller for attaining self-propulsion. Two methods for water-jet performance are used: 1) evaluation of forces based on integration of the stress over the wetted area of the hull and water-jet duct, pump casing, and nozzle (integral method) and 2) ITTC (2005) water-jet test procedure (control volume method). The comparison errors at model (resistance, sinkage, and trim) and full (power and trim) scales are satisfactory using both Froude (Fr) scaled model- and full-scale trial data, including the effects of the interceptors and water jets (WJ) on resistance/power, sinkage, and trim. For the model-scale model without WJs, the negative bottom hydrodynamic pressure near the water-jet inlets are observed without and with the hook simulations, and experiments with the hook. The negative bottom vertical force near the water-jet inlets for the simulations without the hook supports Savitsky’s (2014) assertion that semi-displacement monohulls do not exhibit hydrodynamic lift and disproves Giles’ (1992) assertion to the contrary. The hook and interceptors do not affect the pressure distribution significantly near the water-jet inlets. For the full scale model, the WJs induce bow up trim for the simulations and interpolated (between conditions)- and Fr scaled model-scale experiments. The negative bottom pressure and vertical force near the water-jet inlet for the simulations disprove Giles’ (1992) assertion that the WJs provide additional hydrodynamic lift. This is further supported by the comparisons of the vertical force % thrust vs. inlet velocity ratio for the LCS, with results shown in Bulten (2005) for a high-speed motor yacht. Bulten (2005) shows positive vertical force for inlet velocity ratios ≥ 1.25. However, LCS operates in the regime of an inlet velocity ≤ 1.2; thus, consistent with Bulten (2005), the vertical force is negative. The nonlinear effects between the interceptors and WJs are small such that a linear combination can provide a reasonable approximation.

Security Testing for Naval Ship Combat System Software

Military weapon systems are considered as “system of systems” (SoS). They comprise various equipment based on computers and networks and have been developed using commercial computing technology for several decades. The state-of-the-art weapon systems are information technology (IT) systems, for example, the cyber-physical system. In particular, the naval combat system, which is a weapon system, is a representative system interconnecting a number of equipments by using commercial computing technology. It is a software-based complex system, which produces and shares information about naval tactical situations by interconnecting the various systems installed on ships or remote platforms. Moreover, it performs tactical combat functions automatically or manually for assigned missions. As the core function and performance of the combat system shift from being hardware-centric to software-centric, cybersecurity threats to software that can affect the combat systems may emerge as a novel issue. The failure of the combat system to perform normal combat functions in an actual naval combat situation owing to cybersecurity issues is a very serious risk to naval operations. However, software security testing is not conducted systematically during system development because the cybersecurity of the combat system is evaluated to be less important than its function and performance, resulting in the development of an insecure and vulnerable combat system against cybersecurity threats. To build a secure combat system against cyberattacks, it is important to derive systematic and practical security testing for the combat system software during system development. This paper analyzes the previous researches on a software security test, characteristics of the combat system software, and guidelines for the software security testing of the Korean military’s weapon system development. In addition, it proposes improved software security testing to strengthen the cybersecurity of the combat system based on its characteristics and missions.

함정 전투체계 소프트웨어 보안성시험 수행방안 연구

함정 전투체계 소프트웨어 보안성시험 수행방안 연구

Real-time Recognition Method of The Ship Object Based on Video Image

Target recognition has always been a hot topic in the field of computer vision. In the military field, computer vision has a good application in the research of ship target detection methods based on SAR images, but this type of research is limited to the detection of ship targets, and there is no further identification of ship types. Shipborne tracking radar parasitic TV can obtain clear images of sea surface targets in sea and air background. In order to improve the combat capability of ship combat systems, this paper proposes a video-based ship target recognition method, based on the identification of ship targets. This paper takes the hand-labeled TV video as the research object, and uses the Camshift and Kalman filter to improve the Faster R-CNN calculation framework for the automatic recognition and tracking of the video image ship target in the sea and sky background. The experimental results show that the correct recognition rate of the target model of the ship based on this method is above 90%.

Application of 3D Virtual Ocean Image Simulation in Ship Vision

Li, D.-B., 2019. Application of 3d virtual ocean image simulation in ship vision. In: Gong, D.; Zhu, H., and Liu, R. (eds.), Selected Topics in Coastal Research: Engineering, Industry, Economy, and Sustainable Development. Journal of Coastal Research, Special Issue No. 94, pp. 530–534. Coconut Creek (Florida), ISSN 0749-0208.The marine battlefield situation is an important part of the marine geographical environment information. The three-dimensional visualization of the battlefield situation can give the intelligence officers and commanders a more realistic feeling, which makes them work more smoothly. It is an urgent task for the development of military electronic information systems. The simulation research on the virtual visual image system of the naval ship combat is an important means to analyze the situation of the ocean battlefield. In this paper, a three-dimensional virtual ocean simulation technology based on the mesh topology decomposition of ocean topology is proposed and applied in the ship vision system, this simulation technology makes the 3D virtual ocean have better real-time visual simulation rendering effect, and the viewpoint conversion and viewpoint control are smooth, which improves the authenticity of the ship visual simulation in the three-dimensional marine environment.

Modeling Potential Thresholds of Sacrificial Metallic Coatings for Protection of Al-Mg Alloys in Marine Environments

Repair and replacement of ship structures due to material degradation are high cost drivers in naval platform maintenance. Future ship designs and modernization of existing platforms rely on lightweight aluminum-magnesium (Al-Mg) 5XXX series alloys. A technological gap exists in the predictive capability for lifetime predictions of corrosion preventative sacrificial metallic coatings and identification of the underlying electrochemical, chemical and metallurgical mechanisms that control the potential thresholds for intergranular cracking (IGC) and intergranular stress corrosion cracking (IGSCC). Future ships (e.g. Littoral Combat Ship) which plan to use 5XXX alloys extensively will also be at risk. IGC and IGSCC initiation and growth are both strongly controlled by applied potential (regardless of sensitization level). Potential has been shown to significantly determine whether IGC or IGSCC occurs, onset incubation time and subsequent rates of penetration. Metal-rich primer(s) (MRP(s)) can be used as sacrificial metallic coatings that can control the applied potential across a macro defect site could provide protection against IGC of sensitized Al-Mg alloys. It is currently unknown whether a coating can exert sufficient potential control to mitigate IGC. MRPs (as well as pigmented organic coatings) offer the potential to serve as sacrificial anodes capable of performing this function. A multiphysics finite element package was used to computationally model galvanic protection conditions provided by MRPs in electrical contact with Al-Mg alloy AA5456. Primers included Zn-, Al- and Mg-based MRPs. In addition, pure metals including Mg, Al and Zn were evaluated as galvanic protection systems to validate the model against known mixed potential diagrams. Parametric variables included electrolyte thickness (1 micron to 1 meter) and composition (0.6M and 5.45M (sat’d)) NaCl. Primer evaluation was based on its ability to produce a global galvanic couple potential (Ecouple) below the threshold breakdown/pitting potential of the Mg-rich AA5456 beta-phase (beta-Epit). beta-Epit has been shown to be a critical parameter in the susceptibility of AA5456 to IGC. Sacrificial metallic primers with corrosion potentials (Ecorr) greater than Ecorr of AA5456 were predicted to result in the preferential corrosion of AA5456 based on initial boundary conditions. Zn-based primers exhibit the characteristics for providing galvanic protection to sensitized AA5456 without cathodic polarization at high hydrogen evolution overpotentials.

Experimental Study of Active T-Foil Control of Longitudinal Motions of a Trimaran Hull in Irregular Waves

High-speed ships often experience over larger ship motions in waves. Therefore, highspeed ships without motion control hardly have practical commercial values. Recent years saw wider adoptions of T-foils on high-speed ships, which greatly improve ship performances in waves. In this study, we designed a series of model tests to study the motion-reducing effects of T-foils in waves. Heaves, pitches, and bow accelerations are quantities to be measured in the experimental tests. The study shows that the reduction effects of T-foil-controlled longitudinal motions of a trimaran model are prominent. Comparing with naked model tests, it is found that active T-foil controls may reduce motions of trimaran ships in irregular waves by about 20–30%. In the most favorable case, the reduction is as high as 51%. This study shows that installation of T-foils may dramatically reduce the motions and, thus, provide an efficient control tool to mitigate ship motions in waves. The main aims of the present study were to provide an experimental setup for model testing of an active T-foil control system and determine the control equations. Although the control and actuation systems designed in this study are simple, they do produce the required effects. The model-tested control equations can be used for high-speed foil-type ship design directly if proper similarity ratios are used to project the model test results to real ships. 1. Introduction Increasing the length-to-beam ratio is one of the most effective ways to reduce wave-making resistance so that high speed can be achieved (Ackers et al. 1998). High-speed ships with very slender hulls are, however, not stable. Placing two small side hulls on the port and starboard with displacements less than 10% of the total ship displacements improves the ship's stability greatly. This simple consideration led to the fast development of trimaran hull forms in recent years (Coppola & Mandarino 2001; Degiuli et al. 2003; Oh et al. 2005). Encouraged by the successful sea trials of the 127-m-long littoral combat ship Independence at the speed of 50 knots, researchers move forward to search for new technology to improve the motion performances of trimaran hull forms in waves (Li et al. 2002; Hebblewhite et al. 2007; Jia et al. 2009). This is because high-speed ships are faced with the big challenge of severe oscillations in waves. Too large motion responses in waves would counterbalance the high-speed benefits. Therefore, motion control is crucial for high-speed trimaran ships.

An operational effectiveness analysis of legacy and future mine countermeasures systems using discrete event simulation

This paper conducts an operational analysis of legacy and future mine warfare systems using discrete event simulation. The research focuses on a comparative analysis of the MCM-1 Avenger ship, supported by the MH-53E helicopter, and the Littoral Combat Ship, supported by external unmanned systems, in active, defense mine countermeasures operations. The paper develops architectural representations of the functional activities associated with mine countermeasures operations, as well as architectural representations of past, current, and potential future physical entities involved in minehunting and mine neutralization. Those architectural representations are used as the basis for the development of two distinct discrete event simulation models, one corresponding to legacy (MCM-1 Avenger) operations and another corresponding to future (Littoral Combat Ship) operations. The results of the simulation are analyzed using statistical regression. The regression results indicate that the key performance drivers for both the legacy and future systems show considerable overlap, and also suggest that the legacy assets meet or exceed the performance of future assets in several measures of effectiveness. The simulation model for the future assets is reconsidered to develop recommendations regarding alterations to the future force that enable the future force to exceed the operational performance of the legacy force.

Is Malaysia Defense Industry Geared towards Self Reliance Capability? A Conceptual Analysis

Malaysia defense industry has shown a remarkable achievement in the production, maintenance and supply of defense asset and equipment for the nation. Beginning with the establishment of AIROD in 1976 to support RMAF in aircraft maintenance, the industries has now registered a multi-billion project, with the latest is the production of RM8 billion littoral combat ship (LCS) for the RMN. This paper provides a conceptual analysis on the development of Malaysia self-reliance in the context of defense industry. National self-reliance is defined as the ability of Malaysia to produce, use, maintain and supply major defense asset and equipment without external or foreign support. The approach of the study is qualitative where data are gathered thorough literature study, visit to the defense industrial area and interviewed with the key person in respective industry players for defense. It is found that the nation self-reliance is still in the early stage of development and the way forward is very optimistic if the framework governing the self-reliance is well established. This study provides conceptual analysis on national self-reliance of defense industry in Malaysia.

Testability analysis of ship combat system based on discrete bat algorithm

Testability analysis of ship combat system based on discrete bat algorithm

Military software safety engineering

Based on general investigation of military system and software included, it proposes that safety requirement military software should be captured and validated from the whole system involving software, equipment and system, even military stratagem as well. Software safety process is developed following software developing lifecycle. combining software developing lifecycle of waterfall model, ship combat system design and development, and software safety process, software safety developing procedure is put forward basing on U model involving domain knowledge. An application instance is present to prove the practicability of the study. Research results in this paper including military software safety requirement evolvement model, and development model for military software safety have positive guiding significance to ensure military system safety.

‘Zeal Intelligence and Intrepidity’: Naval irregular warfare and the War of 1812 on the Lakes

The history of the War of 1812 has been dominated by scrutiny of the duelling frigates, squadron actions, and the British blockade of American ports. Yet, during the conflict from 1812 to 1815, sailors and marines were just as likely to be involved in maritime raiding operations and other irregular missions as they were to work the ‘great guns’ in ship versus ship combat. This paper re-examines operations on the Great Lakes, and particularly Lake Ontario, in order to illuminate the role of irregular operations and small unit and small craft actions. These types of operations were common throughout the age of sail, but receive little attention from scholars. In order to broaden the scope of operational naval history, and the understanding of the roles and missions of naval forces, a wider investigation of naval irregular warfare is warranted both in the War of 1812 and across naval history more generally.

운용시험평가 데이터를 활용한 함정 운용가용도 평가 방안 및 사례 연구

Navy forces of ROK asked for more than 90% operational availability in the requirement document of combat ship. This study proposes the evaluation methodology of operational availability with the evaluation process, calculation formula, analysis of operational test data. As the case study, the developed methodology is proved to apply for 00 batch-I naval ship using the data to be acquired during the operational test period. The operational availability by test data was 90.03%, and it was satisfied with objective value 90%. The paper will contribute not only to establish the evaluation methodology of operational availability for combat ship but also other general weapon system.

Experimental Investigation of Trimaran Models in Shallow Water

Experiments were conducted at the U.S. Naval Academy's Hydromechanics Laboratory to determine the effect of finite water depth on the resistance, heave, and trim of two different trimaran models. The models were tested at the same length to water depth ratios over a range of Froude numbers in the displacement speed regime. The models were also towed in deep water for comparison. Additionally, the side hulls were adjusted to two different longitudinal positions to investigate possible differences resulting from position. Near critical speed, a large increase in resistance and sinkage was observed, consistent with observations of conventional displacement hulls. The data from the two models are scaled up to a notional 125-m length to illustrate the effects that would be observed for actual ships similar in size to the U.S. Navy's Independence Class Littoral Combat Ship. Faired plots are developed to allow for rapid estimation of shallow water effect on trimaran resistance and under keel clearance. An example is provided.

Experimental Investigation of Trimaran Models in Shallow Water

Experiments were conducted at the U.S. Naval Academy's Hydromechanics Laboratory to determine the effect of finite water depth on the resistance, heave, and trim of two different trimaran models. The models were tested at the same length to water depth ratios over a range of Froude numbers in the displacement speed regime. The models were also towed in deep water for comparison. Additionally, the side hulls were adjusted to two different longitudinal positions to investigate possible differences resulting from position. Near critical speed, a large increase in resistance and sinkage was observed, consistent with observations of conventional displacement hulls. The data from the two models are scaled up to a notional 125-m length to illustrate the effects that would be observed for actual ships similar in size to the U.S. Navy's Independence Class Littoral Combat Ship. Faired plots are developed to allow for rapid estimation of shallow water effect on trimaran resistance and under keel clearance. An example is provided.