CFD Investigation on Hydrodynamic Resistance of a Novel Subsea Shuttle Tanker

The Subsea Shuttle Tanker (SST) was proposed by Equinor as an alternative to subsea pipelines and surface tankers for the transportation of liquid carbon dioxide (CO2) from existing offshore/land facilities to marginal subsea fields. In contrast to highly weather-dependent surface tanker operations, the SST can operate in any condition underwater. Low resistance is paramount to achieving maximum range. In this paper, the resistance of the SST at an operating forward speed of 6 knots (3.09 m/s) and subject to an incoming current velocity of 1 m/s is computed using Computational Fluid Dynamics (CFD). The Delayed Detached Eddy Simulation (DDES) method is used. This method combines features of Reynolds-Averaged Navier–Stokes Simulation (RANS) in the attached boundary layer parts at the near-wall regions, and Large Eddy Simulation (LES) at the unsteady, separated regions near to the propeller. The force required to overcome forward resistance is calculated to be 222 kN and agrees well with experimental measurements available in the open literature. The corresponding power consumption is calculated to be 927 kW, highlighting the high efficiency of the SST. The method presented in this paper is general and can be used for resistance optimization studies of any underwater vessel.

The influence of the layout features of the trimaran hull on its hydrodynamic resistance

В статье отражена история, состояние развития и сложившаяся тенденция применения аутригеров. Показано как сформировалась терминология по судам данного типа. В статье затронута тема влияния расположения аутригеров на гидродинамическое сопротивление тримарана. Целью работы является получение методики для нахождения гидродинамического сопротивления тримарана. Состояние данного вопроса на сегодня недостаточно изучено т.к. нет четкого ответа при какой схеме по длине и ширине судна необходимо располагать аутригеры для того, чтобы судно могло включить в себя все возможные положительные качества. На основании анализа полученных данных модельных испытаний были построены графики зависимости гидродинамического сопротивления от числа Фруда которые показывают влияние расположения аутригеров по длине и ширине относительно центрального корпуса на гидродинамическое сопротивление тримарана. Сделаны выводы о влиянии размеров аутригеров и их расположения относительно центрального корпуса тримарана на его гидродинамическое сопротивление. The article reflects the history, state of development and current trends in the use of outriggers. It is shown how the terminology for vessels of this type was formed. The article touches on the topic of the influence of the location of outriggers on the hydrodynamic resistance of the trimaran. The aim of the work is to obtain a methodology for determining the hydrodynamic resistance of a trimaran. The state of this issue has not been sufficiently studied to date, since there is no clear answer according to which scheme for the length and width of the vessel it is necessary to place outriggers so that the vessel includes all possible positive qualities. Based on the analysis of the obtained model test data, graphs of the dependence of hydrodynamic resistance on the Froude number were constructed, which show the influence of the location of outriggers along the length and width relative to the central body on the hydrodynamic resistance of the trimaran. Conclusions are drawn about the influence of the size of outriggers and their location relative to the central body of the trimaran on its hydrodynamic resistance.

Experimental study of the resistance to the movement of trimaran vessels

The aim of the work is to develop a method for finding the resistance of a trimaran ship at the initial stages of design, depending on the geometric characteristics of the central hull, outriggers and their mutual position. The program of model tests in the experimental tank is characterized. Based on the analysis of the experimentally obtained data, the graphs of the resistance dependence on the Froude number for the trimaran ship model with the fore, central and stern arrangement of outriggers are presented. A graph of the outriggers’ location influence along the vessel length on its hydrodynamic resistance is also shown. A method for calculating the hydrodynamic resistance for a trimaran vessel at the stages of research design is proposed, which is an adjustment of a single-hull vessel model tests’ recalculation classical principle. One of the developed graphs of the residual drag coefficient dependence on the relative speed according to the Froude number for various central hull geometric characteristics of the vessel, outriggers and their relative position is presented. The analysis of serial model tests made it possible to establish the dependence of the trimaran ship resistance on the geometric characteristics of the central hull and outriggers, and their relative position relative to each other in this study. The method proposed in this work will make it possible to substantiate the best layout of outriggers when solving the problem of optimizing the design elements and characteristics of a trimaran at the research design stage.

Conditions for stability of the “vessel-purse seine” system during purse seining

In the process of tightening the rings of the lower seine line, significant forces of hydrodynamic resistance of the netting can capsize the vessel or pull it into the encircled seine area. There is a risk of damage to the propeller-rudder system of the vessel. The list and trim of a fishing vessel can occur. It affects the safety and comfort of the crew, leads to malfunctions of fishing equipment and mechanisms, and can cause accidents. During the vessel’s operation, there are a number of measures to improve stability. However, when designing fishing equipment, it is necessary to know the forces acting from the seine side on the vessel. The article discusses the relationship between the vessel and the seine during purse seining. On the basis of the developed mathematical model of the tension force of the purse rope, taking into account the geometrical parameters of the warp during purse seining, conditions for stability of the “vessel-purse seine” system were obtained.

Assessment of the impact of the main technological characteristics of wells on the power consumption of pumps

The issue of assessing the impact of the main technological characteristics of wells on the power consumption of pumps is one of the important issues. Based on the analysis of the data obtained in the article, the electric energy consumption of the well pump device the rotational speed of the pump (co); the density of the solution (liquid) (p); the pressure generated by the pump (H); the performance of the pump aggregate (q); depth of the well (H); hydrodynamic resistance (dp); Also, on the basis of the STATISTICA program, the calculation work is carried out, the binding function of the pumps is determined to what extent the factor affects the electricity consumption, and is described in the Pareto diagram.

Separation of Enantiomers through Local Vorticity: A Screw Model Mechanism

We present a model to explain the mechanism behind enantiomeric separation under either shear flow or local rotational motion in a fluid. Local vorticity of the fluid imparts molecular rotation that couples to translational motion, sending enantiomers in opposite directions. Translation-rotation coupling of enantiomers is explored using the molecular hydrodynamic resistance tensor, and a molecular equivalent of the pitch of a screw is introduced to describe the degree of translation-rotation coupling. Molecular pitch is a structural feature of the molecules and can be easily computed, allowing rapid estimation of the pitch of 85 drug-like molecules. Simulations of model enantiomers in a range of fluids such as $\Lambda$- and $\Delta$-Ru(bpy)_3]Cl_2 in water and (R,R)- and (S,S)-atorvastatin in methanol support predictions made using molecular pitch values.A competition model and continuum drift diffusion equations are developed to predict separation of realistic racemic mixtures. We find that enantiomeric separation on a centimeter length scale can be achieved in hours, using experimentally-achievable vorticities. Additionally, we find that certain achiral objects can also exhibit a non-zero molecular pitch.

INCREASING THE EFFICIENCY OF WATER TRANSPORT OF THE FOREST TO INCREASE THE HYDRODYNAMIC PROPERTIES OF THE RAFT

Of all the known modern types of water transport of the forest, the most promising is timber rafting, which, when used, has both positive and negative properties. Negative indicators include such indicators as: seasonality of work, since use in the winter period is impossible, loss of wood when unloading logs onto water and a raft, large dimensions, complexity of management, the need to unload a raft when unloading it. Passes through non-standard sections of the river bed and subsequent formations, special requirements for the dimensions of the waterway, speed limits and others. One of the most acute problems caused by huge hydrodynamic resistance to movement, which increases with an increase in towing speed, is the limitation of the speed of movement of the raft in the water area. In this regard, the maximum speed of the raft in calm weather reaches no more than 1 1.2 m / s, while two or more powerful tugs are involved. The limited time frame for rafting on wooden rafts is due to the flood period during the spring floods and floods, and they have fallen on hard times. Increasing the raft’s allowable towing speed will shorten the raft’s transport time. A decrease in hydrodynamic resistance when the raft is moving will increase the maximum allowable speed of its towing, which will have a positive effect on the efficiency of timber rafting. Based on the analysis of existing known designs of modern rafts, as well as methods of influencing the reduction of hydrodynamic resistance in the field of shipbuilding, a number of methods have been proposed for reducing the hydrodynamic resistance to the movement of the raft. Methods of reducing the resistance to the movement of the raft by changing the features of its formation by placing separate sections or beams in the streamlined material, the introduction of hydrodynamic fairings are considered. The proposed methods for reducing the hydrodynamic resistance can significantly increase the efficiency of timber rafting.

On the equilibrium and stability of a fluidized bed as a thermodynamic system

The transfer of the dispersed layer into a fluidized state makes it possible to intensify the drying process. The small size of the particles leads to an increase in the surface of their contact with the coolant at a relatively low hydrodynamic resistance. Other positive qualities of fluidization are listed, which is very important when carrying out exothermic processes. We studied the behavior of the fluidized bed during the drying process. The curve of fluidization of beet chips is shown. The suspended state of the material began when the forces of the hydrodynamic layer were equal to the weight of all its particles per unit area of the cross-section of the working chamber. The region of existence of the fluidized bed is marked. In this area, the flow was relatively equilibrium (fluidized). On the surface of the layer, small waves were observed with different frequencies and amplitudes of oscillations, as well as with spontaneous fluctuations. This mode of operation was achieved as a result of the study of the structures of the support - gas distribution grid and the drying chamber. The flow velocity profile in the working chamber is investigated. An efficient equalization of velocities with the help of flat stamped grids has been established. The results were confirmed by the spectra of the flow in the drying chamber. Oscillations on the free surface of a fluidized bed are considered. The Euler equation was written, which made it possible, as a result of various transformations, to obtain a formula for calculating the oscillation frequency of the fluidized bed. The studies carried out made it possible to establish the regimes of pseudo-fluidization, to a certain extent minimizing the heterogeneity of the layer, which is of significant practical importance. However, the operating parameters need to be adjusted depending on the type of material to be dried and other indicators. The research results do not obscure the general provisions of nonequilibrium thermodynamics. The fluidized bed cannot be in an equilibrium state, since the transfer of substances is obvious: energy, mass and momentum. It is correct to regard the fluidized bed as unstable. Small and spontaneous fluctuations always exist in the layer. The absence of conditions for their decay becomes a condition for the instability of the process.

Laser Powder Bed Fusion of a Topology Optimized and Surface Textured Rudder Bulb with Lightweight and Drag-Reducing Design

This work demonstrates the advantages of using laser powder bed fusion for producing a rudder bulb of a moth class sailing racing boat via laser powder bed fusion (LPBF). The component was designed to reduce weight using an AlSi7Mg0.6 alloy and incorporated a biomimetic surface texture for drag reduction. For the topological optimization, the component was loaded structurally due to foil wing’s lift action as well as from the environment due to hydrodynamic resistance. The aim was to minimize core mass while preserving stiffness and the second to benefit from drag reduction capability in terms of passive surface behavior. The external surface texture is inspired by scales of the European sea bass. Both these features were embedded to the component and produced by LPBF in a single run, with the required resolution. Drag reduction was estimated in the order of for free stream velocity of . The production of the final part resulted in limited geometrical error with respect to scales 3D model, with the desired mechanical properties. A reduction in weight of approximately with respect to original full solid model from 452 to 190 g was achieved thanks to core topology optimization. Sandblasting was adopted as finishing technique since it was able to improve surface quality while preserving fish scale geometries. The feasibility of producing the biomimetic surfaces and the weight reduction were validated with the produced full-sized component.