Sail Type Research Articles

Distinctive Features of Using the Propulsor of the Underwater Sail Type and the Direct-Flow Wave Propulsor on a Semisubmerged Catamaran

Distinctive Features of Using the Propulsor of the Underwater Sail Type and the Direct-Flow Wave Propulsor on a Semisubmerged Catamaran

Numerical Study on Auxiliary Propulsion Performance of Foldable Three-Element Wingsail Utilizing Wind Energy

Sail-assisted propulsion is an important energy-saving technology in the shipping industry, and the development of foldable wingsails has recently become a hot topic. This type of sail is usually composed of multiple elements, and its performance at different folding configurations is very sensitive to changes in incoming airflow, which result in practical operational challenges. Therefore, original and optimized three-element wingsails (bare and concave) are modeled and simulated using the unsteady RANS method with the k-ω SST turbulence model. Next, certain key design and structural parameters (such as angle of attack, apparent wind angle, and camber) are employed to characterize the auxiliary propulsion performance, and the differences are explained in combination with the flow field details. The results show that, in the unfolded state, the aerodynamic performance of the concave wingsail is better than that of the bare wingsail, exhibiting higher lift coefficients, lower drag coefficients, and a more stable surface flow. In the fully folded state, wherein both the nose and flap are rotated, the thrust performance of the concave wingsail remains superior. Specifically, at an angle of attack of 8 degrees, the thrust coefficient of the concave wingsail is approximately 23.5% higher than that of the bare wingsail, indicating improved wind energy utilization. The research results are of great significance for engineering applications and subsequent optimization design.

Large-Eddy Simulation of Low-Frequency Flow Oscillations for NACA0012 and Dynarig Sail at Large Attack Angles

Unmanned sailboats, harnessing wind for propulsion, offer great potential for extended marine research due to their virtually unlimited endurance. The sails typically operate at high attack angles, which contrasts with aircraft that maintain small angles to prevent stalling. Despite the reduction in lift during stalling, the resultant increase in drag contributes significantly to the sail’s thrust. However, the sail often experiences vortex shedding due to high attack angles, leading to low-frequency oscillations and erratic navigation. This study employs large-eddy simulations (LESs) on a 3D NACA0012 sail at a Reynolds number of 3.6 × 105, which is validated by experimental data. It observes the lift and drag coefficients across attack angles from 5 to 90 degrees and compares these with a Dynarig sail. The findings reveal that higher attack angles amplify fluctuations in lift and drag coefficients. Vortex shedding, resulting from flow separation, creates pressure changes and oscillations in aerodynamic forces. Fast Fourier transformation (FFT) analysis identifies dominant frequencies between 0.5 and 10 Hz, indicating low-frequency oscillations. The study’s insights into the impact of attack angle and sail type on the oscillation frequency are favorable for the design of unmanned sailboats, aiding in the prediction of wind-induced frequencies and optimal attack angle determination.

Design and development of sail type wind turbine with solar panel

The main drivers of economic development of any society very often correlate with the access and use of energy. In fact, proper utilization of the resource requires technology. The industry needs green energy technology for sustainable development. Energy demands can be met by renewable energy sources, as fossil fuels getting depleted day by day. Solar, biomass, geothermal, wind and water energy can be used as the best alternate sources. Wind turbines are capable of extracting power form wind regardless of the direction of flow in both day and night. Solar photo voltaic cells can tap radiation from sun and can be converted in to electrical energy. Hybriding the systems has proved to be beneficial in terms of supplying load demand under varying weather conditions, which in turn make us to use these systems for power generation and overall costs for self-powered system may be reduced drastically, High reliability without backup power source combination is the advantage of this process. In this work also we would like to combine solar PVs and vertical axis wind turbines (VAWT) that can extract electrical energy. The advantages of vertical axis turbines has much better self- starting characters and better conversion efficiency at lower flaw speed. In this we used savonious type vertical axis turbine that produce higher torque and have lower cut in speed. This paper presents the urban Eco- Greenery hybrid wind- solar power generation by using VAWT turbine and solar tracking.

Analysis of Influencing Factors on Lift Coefficients of Autonomous Sailboat Double Sail Propulsion System Based on Vortex Panel Method

Sail is the core part of autonomous sailboat and wing sail is a new type of sail. Wing sail generates not only propulsion but also lateral force and heeling moment. The latter two will affect the navigation status and bring resistance. Double sail can effectively reduce the center of wind pressure and heeling moment. In order to study the effect of distance between two sails, airfoil and attack angle on the total lift coefficient of double sail propulsion system, pressure coefficient distribution and lift coefficient calculation model have been established based on vortex panel method. By using the basic finite solution, the fluid dynamic forces on the two-dimensional sails are computed. The results show that, the distance in the range of 0 to 1 time chord length, when using the same airfoil in the fore and aft sail, the total lift coefficient of the double sail increases with the increase of distance, finally reaches a stable value in the range of one to three times chord length. Lift coefficients of thicker airfoils are more sensitive to the change of distance. The thicker the airfoil, the longer distance is required of the total lift coefficient toward stable. When different airfoils are adopted in fore and aft sail, the total lift coefficient increases with the increase of the thickness of aft sail. The smaller the thickness difference is, the more sensitive to the distance change the lift coefficient is. The thinner the fore sail is, the lower the influence will be on the lift coefficient of aft sail.

Testing a Boat with Different Wave Propulsors in a Hydrodynamic Channel

The paper presents the results of the comparative testing of wave propulsors of five types, including the propulsor of the underwater sail type, a rigid foil with elastic couplings, and a propulsor without movable elements using the effect of the nonlinear interaction between a wave and the working body of the propulsor. The rigid foil operation is numerically simulated using the XFlow software package. The influence of the wave propulsor location on the boat frame, the depth of its immersion, the elastic coupling parameters, and the presence of stabilizing aft devices on the propulsor performance is studied. It is shown that for a rigid swinging wave propulsor with elastic couplings mounted on the bow of a boat the velocity of the boat motion is proportional to the bow swinging.

Implementation of a Fluid-Structure Interaction Solver for a Spinnaker Sail

Abstract. The design of sails has always been done experimentally, and only recently simulations are starting to be used in the design process. This paper presents a solver that couples CFD and FEM in order to compute the deformed sail shape (flying shape) and the thrust it can provide. The complexity of the problem is both in the flow, which is fully turbulent and detached, and in the structure, which is deformable and free to move in all directions. Moreover, the coupling of the solvers has to be performed in a way that minimizes loss of information and accuracy. The CFD simulations have been run and validated with the commercial software FINE/Open. The results were reasonably satisfying when compared to the experimental data obtained by Viola et al. (2014). Consequently, the FEM solver has been successfully validated for some cases of which the analytical solution is known, due to lack of reference data for this specific case. Finally, the interpolation techniques have been implemented in Matlab and the fluid structure interaction solver has been run. From the results it can be argued that the design and flying shape of the sail are quite different and provide different thrusts. This results in the need for this type of analysis in the sail design and manufacturing process: considering the sail as rigid is not enough to have a correct representation of the spinnaker behavior. It is necessary to couple the CFD solver with a finite element solver able to describe the cloth deformation. This is true for all types of sails, but for downwind sails it is particularly important, due to their high deformability with respect to upwind sails.

Hard sail optimization and energy efficiency enhancement for sail-assisted vessel

The shipping industry has valued wind energy in the last decades due to the global increasingly severe environmental situation. The sail-assisted vessels have employed generous types of sails to exploit wind energy and reduce the energy consumption. To meet the ever-increasing energy saving requirements of sail-assisted vessels, this paper investigates the hard sail design optimization and energy efficiency enhancement problems for sail-assisted vessel. By using parametric section airfoil parametrization (PARSEC) method and particle swarm optimization algorithm, we fulfill the optimization of the wingsail aerodynamic design. The performance of our optimized airfoil has been verified by multi-point theory, computational fluid dynamics (CFD) examination, and energy efficiency design index (EEDI) calculation. The maximum lift-to-drag ratio of the coupled wingsails has increased by 10% than that of the arc-shaped sail. And the vessel equipped with our coupled wingsails can remarkably reduce EEDI by 18.2% and 4% when compared to non-sails vessel, and the vessel equipped with variable-camber sail (VCS), respectively.

ISA semantics for ARMv8-a, RISC-v, and CHERI-MIPS

Architecture specifications notionally define the fundamental interface between hardware and software: the envelope of allowed behaviour for processor implementations, and the basic assumptions for software development and verification. But in practice, they are typically prose and pseudocode documents, not rigorous or executable artifacts, leaving software and verification on shaky ground. In this paper, we present rigorous semantic models for the sequential behaviour of large parts of the mainstream ARMv8-A, RISC-V, and MIPS architectures, and the research CHERI-MIPS architecture, that are complete enough to boot operating systems, variously Linux, FreeBSD, or seL4. Our ARMv8-A models are automatically translated from authoritative ARM-internal definitions, and (in one variant) tested against the ARM Architecture Validation Suite. We do this using a custom language for ISA semantics, Sail, with a lightweight dependent type system, that supports automatic generation of emulator code in C and OCaml, and automatic generation of proof-assistant definitions for Isabelle, HOL4, and (currently only for MIPS) Coq. We use the former for validation, and to assess specification coverage. To demonstrate the usability of the latter, we prove (in Isabelle) correctness of a purely functional characterisation of ARMv8-A address translation. We moreover integrate the RISC-V model into the RMEM tool for (user-mode) relaxed-memory concurrency exploration. We prove (on paper) the soundness of the core Sail type system. We thereby take a big step towards making the architectural abstraction actually well-defined, establishing foundations for verification and reasoning.

Power profile for segment rigid sail

ABSTRACTRigid sails have the potential to lower fuel consumption on powered ships by using the wind as a supplementary source of propulsive power. The amount of propulsive power that can be provided by each sail is dependent on a number of variables, which include the sail type, sail area and number of sails deployed. Since each type and size of rigid sail has its own performance characteristics, it is difficult to estimate the propulsive power that could be provided by a particular rigid sail and to make comparisons between different rigid sails. To overcome this problem, a rigid sail power profile is proposed. This power profile will outline key performance characteristics and allow comparisons to be made between different types of rigid sails.

Wing Sails for Hybrid Propulsion of a Ship

Various types of hybrid drives are increasingly being applied in transportation. Wing sails can provide additional propulsion to a motor-driven ship, thereby decreasing fossil fuel consumption. This article contributes to the selection and consideration of the influencing parameters for applying wing sails for ship propulsion. Basic developmental factors and application of wing sails are described. In addition, influential parameters and their relations are discussed. These parameters are connected to the physical and mechanical properties of wing sails and their impact on propulsion. It is important to recognize certain contributions of every influential parameter in relation to the final achievement. Parameters are ranked and described for several common types of sails, to find the best solution. Changing values of the influencing parameters on wing sails can significantly increase converted wind energy. The aim of this study was to note the parameters that influence the wing sail to drive ships more efficiently. Their importance is explained in an example based on the two most important sail types. This article evaluates the main parameters for a pointed semi-rigid wing with additional circulation for hybrid propulsion. All further research should be focused on this wing. Finally, guidelines for structural and operational changes in future wing sails are provided, which may assist developers in directing their efforts to discover a better solution for ship propulsion.

Sail Structure Design and Stability Calculation for Sail-assisted Ships

Ship sail-assisting is a kind of integrated technology involved in fluent dynamic analysis, sail structure design, sail rotation control, ship stability and maneuverability. This paper systematically introduces several aspects of sail-assisting technology. The paper firstly introduces sail type selection and experimental results of arc sail models. Thrust force coefficient, drifting force coefficient, lifting force coefficient, resistance coefficient and rotating torque coefficient of the sail model are discussed and optimal sail rotated angle is calculated in the paper. A control mechanism and the material of sail structure are designed for the sail operation of a ocean-going bulk carrier. Based on stability requirements of ocean-going ships, this paper proposes a stability criterion for sail-assisted ships and suggests a calculation method of stability parameter for the requirements. Comments and recommendations are finally discussed for the further application of the sail onboard ship.

Wrinkle development analysis in thin sail-like structures using MITC shell finite elements

We propose a method of modelling sail type structures which captures the wrinkling behaviour of such structures. The method is validated through experimental and analytical test cases, particularly in terms of wrinkling prediction. An enhanced wrinkling index is proposed as a valuable measure characterizing the global wrinkling development on the deformed structure. The method is based on a pseudo-dynamic finite element procedure involving non-linear MITC shell elements. The major advantage compared to membrane models generally used for this type of analysis is that no ad hoc wrinkling model is required to control the stability of the structure. We demonstrate our approach to analyse the behaviour of various structures with spherical and cylindrical shapes, characteristic of downwind sails over a rather wide range of shape and constitutive parameters. In all cases convergence is reached and the overall flying shape is most adequately represented, which shows that our approach is a most valuable alternative to standard techniques to provide deeper insight into the physical behaviour. Limitations appear only in some very special instances in which local wrinkling-related instabilities are extremely high and would require specific additional treatments, out of the scope of the present study.

Experimental Investigations on Sail Type Wind-Turbines

Horizontal and vertical axis type wind turbines using sails (instead of rigid blades) are experimentally investigated. Cretan type wind turbines are horizontal axis sail type wind turbines. The simple design, low cost and ease of construction of these turbines make them an attractive option for areas having low wind velocities. Coefficient of power and coefficient of torque for Cretan type rotor with 5 blades for a solidity ratio of 0.85 is studied. The type of the cloth used is polyester with porosity ranging between 75 to 300 μm. Experiments are conducted for Reynolds number of 1 × 105 and 1.2 × 105 and tip speed ratios ranging between 0 and 0.1. Influence of sail angle (5°, 15°, 25° and 30°) on the performance of the horizontal axis sail type wind turbines is investigated. Sail angle of 25° gives the maximum coefficient of power of 0.31 at a tip speed ratio of 0.71. Sail Savonius wind turbines are investigated on the vertical wind turbine domain. The enhanced performance of Cretan type wind rotors using sails laid the foundation for studying the behavior of Savonius wind turbines with flexible blades. The sail Savonius rotor used in the study has a rotor diameter of 180 mm with an overlap ratio of 0.15. The type of cloth used is polyester with the porosity ranging between 75 to 300 μm. The performance characteristic curves are measured for Reynolds number of 9 × 104 and 1 × 105. The peak value of coefficient of power is around 0.05 at a tip speed ratio of 0.43 for a Reynolds number of 1 × 105.

Generalized Model for Solar Sails

E define a new methodology for the analytic description of the force and moment generated by a solar sail of arbitrary shape and surface optical properties. We find that the total force and moment generated by the sail can be completely defined by the computation of a number of constants of the sail, which are only functions of the sail geometry and independent of the incident light. Given these constants, some standard sail properties, and the incident light pressure and direction, the total force and moment acting on the sail can be computed using simple formulas. Specifically, we can characterize the force generated by a solar sail of arbitrary sail geometry under general illumination conditions with 18 numbers. To characterize the moment requires an additional 36 numbers. The advantages of this description are that these constants can be computed off-line and are defined for arbitrarily shaped sails, meaning that only one formalism must be coded to deal with all types of sails. There are a number of limits to this approach. First, this model tacitly assumes that the sail will not change shape as its attitude varies, thus their utility might be somewhat limited or constrained to relatively small angular motions. This limitation will be addressed in the future. Second, it assumes that there is no self-shadowing, that is, that every element of the sail surface will “see” an incident ray. This is a reasonable assumption given the likely mode in which a solar sail will be operated.

A Study of Straight Wing with Sail Type Vertical Axis Wind Turbine

A Study of Straight Wing with Sail Type Vertical Axis Wind Turbine

A Study of Straight Wing with Sail Type Vertical Axis Wind Turbine

A Study of Straight Wing with Sail Type Vertical Axis Wind Turbine

Wind tunnel tests and manoeuvre simulator tests with different types of sails and ships

The present paper describes how wind tunnel tests combined with manoeuvring simulator tests and wind statistics can be used to estimate the mean reduction in power consumption for larger ships equipped with sail systems for auxiliary propulsion purposes. The results presented is based on wind tunnel tests with a 60, 000 tdw bulk carrier carried out for the Burmeister & Wain Ship Design in Denmark.

Discussion of “Limit Loads of Wires with Twisted Joints”

In the design of a windmill using a sail type rotor, there arose a need to protect the structure against damage due to overloading in excessive winds. This need was satisfied by using a novel form of load limiter in the support system of sails of the windmill. This note will analyze the load capacity wires so that one can design wires for any specified limit load.

A low-cost water pumping windmill using a sail type Savonius rotor

A water pumping windmill which can be built largely with materials and skills available in rural areas has been designed and fabricated. The windmill uses a Savonius rotor and incorporates a novel sail-type construction. The pump is of a positive displacement type using the casing of a pneumatic tyre for the pumping chamber. Two prototypes have been constructed and these have indicated a reasonable performance and reliability.