Full-scale self-propulsion simulation with a discretized propeller

A comparison between towing tank testing and full-scale CFD simulations is presented at three different target speeds. For the current self-propulsion simulation, the self-propulsion point was obtained using polynomial interpolation. The studies of boundary layer thickness, a basic grid uncertainty assessment and verification were performed to give some confidence of grid application to current self-propulsion simulation. All simulations are performed using a commercial CFD software STAR-CCM+. It is concluded that with high-fidelity numerical methods, it’s possible to treat hull roughness and directly calculate full-scale flow characteristics, including the effects of the free surface, none-linearity, turbulence and the interaction between propeller, hull and the flow field.

Brief analysis of foreign experience in arrangement of purchasing weapons and military equipment

for weapons, military and special-purpose equipment, supplies and services to support military forces of five states, which are world leaders in the military field: USA, UK, France, Germany and China. A special emphasis is made on shipbuilding. Materials and methods. The review is based on modern strategic documents and legislative acts regulating the procurement activities of major state military agencies. Main results. A detailed consideration is given to specific procurement systems operating in foreign countries, similar features and differences are identified, national specifics are mentioned. Recommendations are given regarding lessons to be learned by Russian military departments. Conclusions. Based on the foreign experience it is found advisable to combine centralized purchasing of major military products and equipment and decentralized procurement of some general-purpose items.

Effect of water resistance on predictions of ship ice resistance using towing tests in ice basin

Object and purpose of research. The object under study is a method to determine ice resistance using towing tests of ship models. The purpose of the work is to develop a method that takes into account the water resistance effect on predictions of full-scale ship ice resistance. Materials and methods. The materials for development are model test data and earlier methods for determination of ice resistance on models, as well as recommendations of the International Towing Tank Conference (ITTC). Main results. The method is suggested to take into account the water resistance in analyzing the towing test data obtained in the ice basin, as well as the method for extrapolating the ice resistance due to hydrodynamic interaction of ice floes with underwater hull, including the scale effect. Conclusions. The methods that take into account the water resistance effect on predictions of ship ice resistance based on towing test data obtained in ice basins are reviewed and analyzed. An improved method to include the water resistance effect in a more correct way is suggested. For better comparison of test results in ice basin it is required to introduce a common method of including the water resistance effect using the method suggested in this work.

Effect of submerged body shape upon its movement pattern near free surface

Object and purpose of research. This paper discusses the tests with submerged models of different shape moving near the free surface in the test tank. The purpose of the study was to determine how relative vertical displacement and crosssection shape lift of submerged body depend on the speed of its movement at different immersion depths. Materials and methods. Model test procedure, techniques and results of model. Numerical simulation was performed in ANSYS software package. Main results. Experimental and theoretical study on cross-section shape effect of submerged body upon its wave generation, vertical lift and movement pattern near free surface. Conclusion. The results of this research will be useful for further work towards greater horizontal movement stability of submerged body at various speeds depending on its hull shape and immersion depth.

Seakeeping index as generalized indicator of ship seakeeping performance

Object and purpose of research. This paper discusses the possibility of a ship design process that would consider seakeeping performance to the greatest extent possible. The purpose of this study was to work out a numerical indicator, an index, reflecting all the seakeeping properties relevant for suitability of given ship to its intended operational conditions. Materials and methods. The study was based on the data about various operational parameters of the ship under investigation. These data were further synthesized so as to obtain the most comprehensive picture of ship seakeeping behaviour in different operational conditions. Main results. The study yielded the method and the algorithm for the “seakeeping index” as an average annual probability that seakeeping performance of given ship will be adequate to the conditions of given water area. The method sug-gested in this paper for a generalized comparison of seakeeping properties can handle whatever variety of target parameters and whatever seakeeping standards for any kind of ship intended to operate in given water area, and the result of this comparison is given in form of a single number that can be further used to improve seakeeping parameters of given ship, as well as to estimate possible time of its fully-featured operation in given conditions, including cost efficiency analysis. Conclusion. For more accurate comparison, it is recommended to analyse target parameters as functions of both ship speed and wave heading angle keeping in mind that the assumption introduced, i.e. that these curves as functions of wave heading angle are cosines, is not necessarily true. In other words, it is recommended to rely on more accurate data, experimental or analytical, so as to take into account the effect of apparent frequencies upon these curves.

Estimation of compressive and tensioning forces in linear storages of electric power

Object and purpose of research. Electromagnetic forces in thin-walled coils of toroidal type and common type of different cross-sections (circular, rectangular, disk, spherical) are estimated and compared. Materials and methods. Methods of theoretical electric engineering are used. Main results. It is established that forces for toroidal and common coils have different character. First, there is an effect of centripetal compression, secondly, there is an effect of centripetal tensioning. Conclusions. These effects should be taken into account in the coil design, which have to withstand deformation or damage under compressive or tensioning forces.

Specifics of turbo-alternator design with a high rotational speed of 6000 rpm

Object and purpose of research. The object under study is a 36 МW turbo-alternator (TA) with electromagnetic excitation and a high rotational speed of 6000 rpm, which can be used as an option for ac electric power source of 100 Hz in ship electric power systems with a turbo-alternator plant. The purpose is to perform electromagnetic calculations to determine TA main data and technical characteristics, including the stator and rotor pack, their design, mass of active materials, etc. for comparison with a TA of the same power but 3000 rpm. Materials and methods. The studies are based on research and engineering data about investigations and design of double-pole industrial TA of 50 Hz as well as TA with a high current frequency (100 Hz and higher). For this purpose, the known formulas were used to estimate the size of TA active elements, excitation forces of stator and rotor windings, as well as methods for calculation of main TA parameters and technical characteristics. Main results. Design specifics of TA with a high rotational speed of 6000 rpm is identified, and results of electromagnetic estimations are obtained for a specific 36 MW turbo-alternator of 100 Hz with a forced close cycle cooling and better mass and size characteristics. Conclusions. The obtained results are of practical value, showing feasibility of developing a version of 36.0 МW TA with a rotational speed of 6000 rpm and significantly reduced specific mass and size characteristics – tentatively by 35–40 % as compared to the existing TA of the same power but with a speed of 3000 rpm.

Multi-mode adaptive-pitch propeller and its application prospects for ships with variable running conditions

Object and purpose of research. This paper describes multi-mode adaptive-pitch propeller and its hydrodynamics. Based on the calculation data, the study demonstrates that this kind of propeller might be quite promising in terms of propulsion performance for the ships with variable running conditions, like patrol vessels that switch between patrol and chase running mode. More-over, multi-mode adaptive pitch propellers may work as two-positional CPPs commonly regarded as general-use propellers. These results might be useful in design of ships for various applications. Materials and methods. Experimental data on hydrodynamic parameters of multi-mode adaptive pitch propeller and design calculation results for a virtual triple-shaft patrol vessel. Main results. The results of this study could be useful in propeller selection for given ship design. Conclusion. It is shown that, as compared to FPPs, multi-mode adaptive pitch propellers are more efficient in terms of propulsion performance.

Dissipative properties of composite structures. 1. Statement of problem

Object and purpose of research. The object under study is a sandwich plate with two rigid anisotropic layers and a filler of soft isotropic viscoelastic polymer. Each rigid layer is an anisotropic structure formed by a finite number of orthotropic viscoelastic composite plies of arbitrary orientation. The purpose is to develop a mathematical model of sandwich plate. Materials and methods. The mathematical model of sandwich plate decaying oscillations is based on Hamilton variational principle, Bolotin’s theory of multilayer structures, improved theory of the first order plates (Reissner-Mindlin theory), complex modulus model and principle of elastic-viscoelastic correspondence in the linear theory of viscoelasticity. In description of physical relations for rigid layers the effects of oscillation frequencies and ambient temperature are considered as negligible, while for the soft viscoelastic polymer layer the temperaturefrequency relation of elastic-dissipative characteristics are taken into account based on experimentally obtained generalized curves. Main results. Minimization of the Hamilton functional makes it possible to reduce the problem of decaying oscillations of anisotropic sandwich plate to the algebraic problem of complex eigenvalues. As a specific case of the general problem, the equations of decaying longitudinal and transversal oscillations are obtained for the globally orthotropic sandwich rod by neglecting deformations of middle surfaces of rigid layers in one of the sandwich plate rigid layer axes directions. Conclusions. The paper will be followed by description of a numerical method used to solve the problem of decaying oscillations of anisotropic sandwich plate, estimations of its convergence and reliability are given, as well as the results of numerical experiments are presented.

Methods and equipment for power supply of underwater vehicles

Object and purpose of research. The object of the work is the power supply systems of submersibles. The aim is to assess the characteristics of the submersible energy supply systems and find ways to improve them. Materials and methods. The study was conducted on the basis of analytical methods and computer simulation of electromagnetic processes of the systems of energy supply of submersibles. Main results. A comparative assessment of the characteristics of the main systems of energy supply of submersibles has been carried out. New ways and devices powering submersibles, developed methods for calculating these devices. Ways to improve the power supply systems of submersibles are shown. Conclusion. The results of the research allow us to identify ways to further improve the characteristics of the power supply systems of submersibles and to speed up the process of their implementation in practice.