Field Of Hydrodynamics Research Articles

Уменьшение гидродинамической силы в гидрораспределителе путем модернизации деталей золотниковой пары

Due to a sharp change in the direction and velocity of the fluid flow in the hydraulic distributor, hydrodynamic forces arise. When positioning and holding the spool, the magnitude of the above forces determines the required control power. The aim of the article was to find an optimal constructive solution that would reduce the influence of hydrodynamic forces. In the article we have considered the theoretical foundations laid in the analytical solution of the problem of calculating the magnitude of the hydrodynamic force acting on the plunger of the spool. In addition, a numerical experiment was carried out using CAD Solidworks and the Flow Simulation application package and a comparison of the results obtained with the analytical solution of the problem. During the numerical experiment, it was found that by upgrading the spool sleeve, it is possible to reduce the value of the hydrodynamic force by 4.5 times, compared with the original design. At the same time, it was found that the modernization of the plunger does not further reduce the maximum hydrodynamic forces. The article highlights the economic benefits of reducing the required power to control the hydraulic distributor. The article may be of interest to both researchers whose research interests lie in the field of hydrodynamics, and manufacturers of hydraulics.

Experimental study of flow dynamics of a sweeping jet in a slot channel

In recent years, fluidic oscillators have been actively applied as devices for flow control in the field of aero and hydrodynamics. This study aims to investigate the structure of a flow of sweeping jet ejected from a fluidic oscillator into a confined area – slot channel. Dynamics of sweeping jet flow are investigated using the PIV method with high temporal resolution. The effect of the Re number on the sweeping jet oscillation frequency was studied in the range from 1 500 to 8 000. Linear frequency dependence on Re number was obtained. Bounding walls affect the dynamics of sweeping jet flow that leads to a change of average velocity field. For low Re numbers, obtained results are in good agreement with the results of other studies.

Evolutionary dynamics of solitary wave profiles and abundant analytical solutions to a (3+1)-dimensional burgers system in ocean physics and hydrodynamics

In the fields of oceanography, hydrodynamics, and marine engineering, many mathematicians and physicists are interested in Burgers-type equations to show the different dynamics of nonlinear wave phenomena, one of which is a (3+1)-dimensional Burgers system that is currently being studied. In this paper, we apply two different analytical methods, namely the generalized Kudryashov (GK) method, and the generalized exponential rational function method, to derive abundant novel analytic exact solitary wave solutions, including multi-wave solitons, multi-wave peakon solitons, kink-wave profiles, stripe solitons, wave-wave interaction profiles, and periodic oscillating wave profiles for a (3+1)-dimensional Burgers system with the assistance of symbolic computation. By employing the generalized Kudryashov method, we obtain some new families of exact solitary wave solutions for the Burgers system. Further, we applied the generalized exponential rational function method to obtain a large number of soliton solutions in the forms of trigonometric and hyperbolic function solutions, exponential rational function solutions, periodic breather-wave soliton solutions, dark and bright solitons, singular periodic oscillating wave soliton solutions, and complex multi-wave solutions under various family cases. Based on soft computing via Wolfram Mathematica, all the newly established solutions are verified by back substituting them into the considered Burgers system. Eventually, the dynamical behaviors of some established results are exhibited graphically through three - and two-dimensional wave profiles via numerical simulation.

A SOLUTION TO STEFAN PROBLEM USING EULERIAN TWO FLUID VOF MODEL

A novel approach for the solution of Stefan problem within the framework of the multi fluid model supplemented with Volume of Fluid (VOF) method, i.e. two-fluid VOF, is presented in this paper. The governing equation set is comprised of mass, momentum and energy conservation equations, written on a per phase basis and supplemented with closure models via the source terms. In our method, the heat and mass transfer is calculated from the heat transfer coefficient, which has a fictitious function and depends on the local cell size and the thermal conductivity, and the implementation is straightforward because of the usage of the local value instead of a global parameter. The interface sharpness is ensured by the application of the geometrical reconstruction scheme implemented in VOF. The model is verified for three types of computational meshes including triangular cells, and good agreement was obtained for the interface position and the temperature field. Although the developed method was validated only for Stefan problem, the application of the method to engineering problems is considered to be straightforward since it is implemented to a commercial CFD code only using a local value; especially in the field of naval hydrodynamics wherein the reduction of ship resistance using boiling flow can be computed efficiently since the method handles phase change processes using low resolution meshes.

A Transatlantic Dialogue of the Tostoy Family Descendants, Participants in “The Golden Book of the Russian Emigration” Project

This article is devoted to the little-known but important details of a large-scale project of publishing a summarizing work on the life and activities of the post-1917 Russian emigration, named “The Golden Book of the Russian Emigration”. This project was conceived in the midst of the Society for the Protection of Russian Cultural Values Abroad in Paris (“OORKTs”) that was founded by D. P. Riabouchinsky, a prominent Russian émigré scientist in the field of aero and hydrodynamics, member of the French Academy of Science. In 1961, Riabouchinsky became the Chair of the Special European Executive Committee (Paris) for the Publication of the “Golden Book”. The American initiative group for the preparation and publication of the “Golden Book” was set up in September 1961. It was headed by Alexandra Lvovna Tolstaya, the daughter of Leo Tolstoy and president of the Tolstoy Foundation (US). This article introduces for scientific use the previously correspondence between A. L. Tolstaya and Sergei Mikhailovich Tolstoy, Leo Tolstoy’s grandson, a doctor of medicine and deontologist, the author of works in tropical medicine and blood transfusion, who chaired the Special European Executive Committee for the Publication of the “Golden Book” since 1967. This correspondence that covers the period of 1966–1967 is concerned with establishing organizational relations between two centers of Russian dispersion, Paris and New York, and sheds light on the complicated workings of interpersonal relationships of project participants and on some causes of the project’s failure. The documents from two “Russian” archives in the USA, the Archive of the Russian Academic Group in the USA and the Archive of the Tolstoy Foundation, were used during the preparation of this article.

Formation and dynamics of quantum hydrodynamical breathing-ring solitons

We show that exciton-polariton condensates may exhibit a new fundamental, self-localized nonlinear excitation not seen in other quantum hydrodynamical systems, which takes the form of a dark ring shaped breather. We predict that these structures form spontaneously and remain stable under a combination of uniform resonant and nonresonant forcing. We study single ring dynamics, ring interactions and ring turbulence, and explain how direct experimental observations might be made. We discuss the statistics of ring formation and propose an experimental scheme by which these structures may be exploited to study the smooth cross-over between equilibrium and non-equilibrium critical phase transitions. Finally, we present an alternative mechanism of formation for these topological breathers, in which they circumscribe Gaussian resonant pumps. The observation of a breathing ring soliton would represent the first fundamental breathing soliton within the broad field of quantum hydrodynamics.

ВЛИЯНИЕ РЕЖИМОВ НАПЛАВКИ НА ХАРАКТЕРИСТИКИ ТЕПЛОМАССОПЕРЕНОСА ЭЛЕКТРОДНОГО МЕТАЛЛА, ФОРМИРОВАНИЕ СТРУКТУРЫ И СВОЙСТВ ПОКРЫТИЙ

The peculiarities of structure formation in coatings deposited under conditions of controlled heat and mass transfer with the pulse change of power parameters of the mode are considered. 
 It is shown that as a result of the pulse control of mode power parameters, in a coating there is observed of structural heterogeneity decrease on a coating section at the expense of the decrease of structural constituent dimensions in it that increases considerably of operation properties of strengthened products operated under conditions of low temperatures of the extreme North. The investigations are carried out with the use of the complex of fast processes of heat and mass transfer that ensured high productivity of the investigation process at lower cost of time and material costs. 
 It is recommended for a wide range of experts in the field of modern physical material science, hydrodynamics, chemistry and mechanics of a deformable solid, reliability and technogenic safety, control of fast processes of the formation of permanent connections modified with pulse high-energy impact.

Hydrodynamics of Biomimetic Marine Propulsion and Trends in Computational Simulations

The aim of the present paper is to provide the state of the works in the field of hydrodynamics and computational simulations to analyze biomimetic marine propulsors. Over the last years, many researchers postulated that some fish movements are more efficient and maneuverable than traditional rotary propellers, and the most relevant marine propulsors which mimic fishes are shown in the present work. Taking into account the complexity and cost of some experimental setups, numerical models offer an efficient, cheap, and fast alternative tool to analyze biomimetic marine propulsors. Besides, numerical models provide information that cannot be obtained using experimental techniques. Since the literature about trends in computational simulations is still scarce, this paper also recalls the hydrodynamics of the swimming modes occurring in fish and summarizes the more relevant lines of investigation of computational models.

Residual Resistance of Displacement Vessels

The hydrodynamics of the residual resistance of ships is formulated for the first time: the residual resistance of vessel displacement is the result of the formation of retaining bow waves, Kelvin wave systems and their interaction—as well as the action of viscosity, which is expressed in the form of a turbulent subsurface boundary layer. Michell’s integral is taken as a basis for calculations of residual resistance. The two corrections take into account the shear layer of wave surface and the shift of the Kelvin bow system by the retaining waves. The correlation of the calculated and experimental curves confirms the validity of the described hydrodynamics of residual resistance. This article is intended for specialists in the field of hydrodynamics of displacement vessels and for designers of the ship hull.

A posteriori error and uncertainty estimation in computational ship hydrodynamics

The increasing relevance of simulation-based design has created a need to accurately estimate and bind numerical errors. This is particularly relevant to full-scale computational ship hydrodynamics, where measurements are difficult and expensive, simultaneously requiring a high degree of predictive accuracy even in early design stages. However, the field of ship hydrodynamics has yet to fully exploit the enhanced capabilities and potential benefits numerical verification methods have to offer. The present study presents a detailed application of numerical verification procedures in CFD as applied to local parameters, such as free surface elevation and skin friction. This is done in order to pinpoint specific locations in the computational domain responsible for heightened levels of error and uncertainty. Relationships between different parameters are demonstrated and discussed based on a set of full-scale simulations of the KCS advancing through a canal using CFD.

ФУНДАМЕНТАЛЬНЫЕ ИССЛЕДОВАНИЯ В ОБЛАСТИ ТЕПЛОФИЗИКИ ЯЭУ: ДОСТИГНУТЫЕ РЕЗУЛЬТАТЫ И ПРОБЛЕМЫ ДАЛЬНЕЙШИХ ИССЛЕДОВАНИЙ

The results of experimental and theoretical calculations of fundamental research in the field of hydrodynamics, heat transfer, physical chemistry and nuclear power technology cooled by water and liquid metal coolants are analyzed, problems and tasks of further research are formulated. The effects and physical phenomena, laws and characteristics for a wide range of processes occurring in the first and second circuits of reactor facilities, including the flow part, the core, the heating equipment, the means of monitoring and cleaning coolants from impurities as applied to watercooled thermal neutron reactors, fast liquid metal reactors, fusion plants, etc. Particular attention in the field of hydrodynamics and heat transfer is given to studies of the heat transfer crisis in watercooled reactors, hydrodynamics of collector systems, stratification and mixing of jets, vibroacoustics, turbulent transfer in complex channels, heat transfer in the channels and assemblies of fast reactor fuel elements, contact thermal resistance, boiling in large volume and bundles of fuel rods, condensation of liquid metals. In the field of physical chemistry and the technology of liquid metal coolants, the types of impurities and the sources of their entry into the coolants for various nuclear power plants, the characteristics of the mass and heat transfer processes in the circuits and equipment of reactor facilities with liquid metal coolants (sodium, potassium, lithium, lead, bismuth lead), the efficiency of using various purification devices (cold and hot traps) and monitoring the state of impurities in coolants are analyzed.Problem questions and suggestions for further research are formulated. Information is given on the key thermophysical problems of basic research in relation to the development of innovative nuclear energy technologies: water-cooled reactors with supercritical water pressure, high-temperature fast reactors with sodium coolant for hydrogen production, thermonuclear installations, nuclear power plants with liquid-metal space coolants.

Academician CAIUS IACOB – a Brilliant Mathematician Fascinated by Mechanics

The paper presents some interesting aspects related to the biography and works of Romanian mathematician Caius Iacob (1912–1992). He was famous for his works in the fields of mathematical analysis, fluid mechanics, classical hydrodynamics and compressible-flow theory. At the age of 19, he graduated from the Mathematics Faculty in Bucharest, and then he went to Paris to continue his studies at the Faculty of Sciences, where he worked on a PhD thesis under the advice of famous French mathematician Henri Villat. On 24 June 1935, Caius Iacob successfully presented to the Sorbonne committee his PhD thesis about “Determination of conjugated harmonic functions with some limit conditions, and their applications in hydrodynamics”. Returning to Romania, Caius Iacob had a long and successful career teaching mathematics and mechanics at the universities of Timişoara, Cluj and Bucharest. His most important work is considered the “Mathematical introduction to the mechanics of fluids”. This book, providing original ways to work with classical hydrodynamics and compressible-flow theory, was published in Romanian in 1952 and in French in 1959. In 1955, he was elected a Corresponding Member of the Romanian Academy, becoming a titular Member in 1963. He was also President of the Mathematics Section of the Romanian Academy from 1980 until the end of his life, in 1992. In 1991, he initiated the foundation of the “Romanian Academy Institute of Applied Mathematics”. In 2001 the institute merged with the “Centre for Mathematical Statistics”, which had been created in 1964 by mathematician Gheorghe Mihoc, thus creating the “Gheorghe Mihoc – Caius Iacob Institute of Mathematical Statistics and Applied Mathematics” of the Romanian Academy.

Propeller performance on a model ship in straight and steady drift motions from single blade loads and flow field measurements

In the field of marine hydrodynamics, propeller operations in off-design conditions represent a challenging topic that has been increasingly attracting interest among industry and research institutions. Over the ship operating life, off-design conditions and the associated modifications of the propeller inflow are connected to a wide range of events such as degradation of the overall efficiency, amplification of unwanted side effects of propeller operations (pressure pulses, vibration and noise) and, ultimately, failure of the ship propulsion system. In this work, the performance of a propeller operating in off-design conditions is investigated by a comprehensive experimental activity aimed at synthesizing the cause-and-effect relation between the propeller loads and its inflow. To this purpose, two novel set-ups are employed: the first one is dedicated to the measurement of single blade loads, whereas the second, a boroscopic-based Stereo-PIV (SPIV) system, is focused on the inflow analysis. The overall measurement apparatus is installed on a twin-screw ship model. Experiments, carried out in the CNR-INM towing tank, consist of straight ahead and steady drift motions at drift angles ±13∘ and ±27∘. This test matrix is representative of weak and tight maneuvering conditions.

An improvement of interface computation of incompressible two-phase flows based on coupling volume of fluid with level-set methods

ABSTRACTA coupling technique for interface simulations applied to the fields of ship hydrodynamics and multiphase flow computations is presented. The technique takes advantages of mass conservation property of the volume-of-fluid method and sharpened interface computation of the Level-Set approach. An improved scheme for the gradient computation of the Level-Set function during re-initialisation is also introduced. A solver with the present coupling is built into the interFoam solver of the OpenFOAM platform. Three test cases, i.e. a free rising air bubble in still water, dam-break simulation with a hump in dry bed channel and free surface flow around a container ship are conducted to demonstrate the capability of the new solver. A good agreement between the simulated results and the benchmark and/or measured data shows the significant potential of the present technique in both academic research and practical applications.

Miniaturization as One of the Paths to Process Intensification in Chemical Engineering

Miniaturization of chemical equipment is one of process intensification methods. The main advantage of microstructured chemical equipment originates from the small cross sizes of microchannels (2–3 mm or less, usually less than 1 mm). Thus, the capillary and viscous forces dominate over the inertial and gravitational forces, leading to the formation of structured flows. The microsized reactors, mixers, heat exchangers, extractors, etc., have the following significant advantages: (1) lower mass and heat losses during processing; (2) better temperature control of processes; (3) shorter diffusional paths for molecules and ions; (4) ultimate safety due to a small reaction volume; (5) much higher heat and mass transfer rates as compared to macrolevel devices; and (6) narrow residence time, consequently, better selectivity and yield. This special issue includes several papers in the field of hydrodynamics and heat and mass transfer in two-phase flows in microchannels.

Perspectives on spin hydrodynamics in ferromagnetic materials

The field of spin hydrodynamics aims to describe magnetization dynamics from a fluid perspective. For ferromagnetic materials, there is an exact mapping between the Landau-Lifshitz equation and a set of dispersive hydrodynamic equations. This analogy provides ample opportunities to explore novel magnetization dynamics and magnetization states that can lead to potential applications that rely entirely on magnetic materials, for example, long-distance transport of information. This article provides an overview of the theoretical foundations of spin hydrodynamics and their physical interpretation in the context of spin transport. We discuss other proposed applications for spin hydrodynamics as well as our view on challenges and future research directions.

Modeling and Simulation of Moored-Floating Structures Using the Tension Element Method

The derivation of a discrete mooring model for floating structures is presented in this paper. The method predicts the steady-state solution for the shape of an elastic cable and the tension forces under consideration of static loads. It is based on a discretization of the cable in mass points connected with straight but elastic bars. The successive approximation is applied to the resulting system of equations which leads to a significant reduction of the matrix size in comparison to the matrix of a Newton–Raphson method. The mooring model is implemented in the open-source computational fluid dynamics (CFD) model REEF3D. The solver has been used to study various problems in the field of wave hydrodynamics and fluid–structure interaction. It includes floating structures through a level set function and captures its motion using Newton and Euler equations in six degrees-of-freedom (6DOF). The fluid–structure interaction is solved explicitly using an immersed boundary method based on the ghost cell method. The applications show the accuracy of the solver and the effects of mooring on the motion of floating structures.

Biophysical Interactions in Fragmented Marine Canopies: Fundamental Processes, Consequences, and Upscaling

Spatial fragmentation is a near-ubiquitous characteristic of marine canopies. Biophysical interactions with fragmented canopies are multi-faceted and have many significant implications at multiple scales. The aims of this paper are to review research on biophysical interactions in fragmented marine canopies, identify current gaps in knowledge and understanding, and propose ways forward. Although fragmented landscapes may be analyzed with relatively sophisticated approaches based on gradients and non-linear ecosystem interactions, it is argued that a simpler conceptualization in terms of patches and gaps is appropriate in this context. The review starts at the patch/gap scale and focuses initially on hydrodynamic interactions. It then considers the consequences of these interactions for particulate and dissolved material, and distributions of canopy-associated organisms. Finally, it addresses issues of upscaling to landscape scale and ways in which this research can be applied to marine landscape management, conservation and restoration. Work on a broad range of canopy types is considered, including micro-algal biofilms and turf algae; macro-algae, seagrasses and coral reefs; saltmarsh vegetation and mangroves. Although the focus is on marine canopies, insights from studies of fragmented canopies in other contexts are drawn on where relevant. These include freshwater environments and terrestrial forests, grasslands, crop canopies and urban areas. Specific areas requiring greater attention are highlighted. The review finds that more studies are needed of: wave interactions with patches and gaps; three-dimensional biophysical interactions with gaps; and biophysical interactions with fuzzy or indistinct patch/gap boundaries. More cross-comparisons of studies of hydrodynamic interactions with different types of canopies are also required. The primary obstacle to progress in this field is found to be the current gap between the most common scale for measurement and modelling – the patch/gap scale – and landscape scale, at which the insights delivered by research may be applied most usefully. Therefore, upscaling is identified as the most important current problem in this field. To address this, a combination of the recently-founded fields of eco-mechanics and hydrodynamics of aquatic ecosystems that balances physical, biological and other perspectives, rather than viewing one as being served by the others, would be the best way forward.

Simulations of Self-Propelled Fully Appended Ship Model at Different Speeds

With the great progress in supercomputers and numerical methods, the applications of computational fluid dynamics are advancing rapidly in the field of ship hydrodynamics. And the dynamic overset grid method makes it possible for computing complex ship motions. In the present work, CFD-based method coupling with dynamic overset grid technique is applied to investigate the hydrodynamic performance of the fully appended ONR Tumblehome ship model during self-propulsion condition. Open water performance of propeller and towing condition of bare hull are computed before the self-propulsion simulation. The ship model is fitted with twin rotating propellers and twin static rudders, achieving self-propulsion model point at [Formula: see text] and [Formula: see text], respectively. All the computations are carried out by our in-house CFD solver naoe-FOAM-SJTU, which solves the Navier–Stokes equations for unsteady turbulent flows with VOF method capturing free surface around the complex geometry models. During the self-propulsion simulation, a feedback controller is used to update the rotational speed of the propeller to achieve the target ship speed. Detailed information of the flow field during the self-propulsion condition is presented and analyzed. In addition, predicted results, i.e. self-propulsion model point, ship motions and force coefficients, are also presented and compared with the available experimental data. Good agreements are achieved, which indicates that the present approach is applicable for the self-propulsion simulation.

Review of pipeline span analysis

PurposeThe purpose of this paper is to mainly review the state-of-the-art developments in the field of hydrodynamics of offshore pipelines, identifying the key tools for analysis of pipeline free spans, their applications, their qualifying characteristics and capabilities and limitations.Design/methodology/approachThese different analytical, numerical and semi-empirical tools available for predicting such hydrodynamic loads and their effects include VIVANA, PIPESIN, VIVSIM, SIMULATOR, FATFREE, amongst others. Inherent in these models are current effects, wave effects and/ or pipe–soil interactions.FindingsAmongst these models, the most attention was given to the new VIVANA model because this model take into account the vortex-induced effects with respect to free-spanning pipelines (which have dominant effect in the span analysis in deep water) better than other semi-empirical models (such as Shear 7). Recent improvements in VIVANA include its ability to have arbitrary variation in speed and direction of current, as well as the ability for calculation of pure IL and combined IL-CF response. Improvements in fatigue assessments at free spans, i.e. pipe–soil interaction have been achieved through the combined frequency domain and non-linear time domain analysis methodology adopted. Semi-empirical models are still the de facto currently used in the design of free-spanning pipelines. However, there is need for further research on free-span hydrodynamic coefficients and on how in-line and cross-flow vibrations interact. Again, there is still the challenge due to VIV complexity in fully understanding the fluid structure interaction problem, as there is no consolidated procedure for its analysis. It has been observed that there is large scatter between the different codes adopted in the prediction of fatigue damage, as there lacks full-scale test data devoted to determination/validation of the coefficients used in the semi-empirical models. A case study of the preliminary design of a typical 48 in. pipeline has been presented in this study to demonstrate the use of the free-span analysis tool, DNV RP F105. Excel spreadsheet has been applied in the execution of formulas.Originality/valueThis review paper is the first of its kind to study the state-of-the-art development in pipeline free-span analysis models and demonstrate the use of analysis tool, DNV for MAFSL calculation. Hence, information obtained from this paper would be invaluable in assisting designers both in the industry and academia.