Foil System Research Articles

Numerical investigations on Hydrofoil Performance due to Homogeneous Roughness

Adding a foil system to catamaran shups, also known as Hydrofoil Supported Catamarans (hysucat), is one method of reducing energy consumption and carbon emissions. By taking advantage of the lifting force of the foil, the implementation of a foil system can efficiently decrease a vessel’s draft and consequently reduce the ship’s resistance. However, continually submerged areas of the ship’s hull will be vulnerable to biofouling. As biofouling grows, the hull becomes rough. As a result of increased frictional resistance, rough surfaces may lower the performance of a system, according to fluid mechanics. This study aims to investigate the impact of foil roughness on its work performance. To achieve this, a computational fluid dynamics (CFD) numerical method will be set up with a modified wall function employed for roughness modelling in simulation. The specified roughness height values (ks ) values, which range from 81.25 to 325.00 to 568.75 in µm, represent the general hull roughness. The results reveal that a rough surface may negatively affect the hydrofoil’s operational performance by raising the resistance significantly.

The performance of a self‐adherent foil system for the corrosion protection of steel substrates for offshore wind tower structures

AbstractThe application of multilayer organic protective coating systems with conventional liquid spray methods is complex, time‐ and energy‐consuming, and it requires extensive technical equipment. An alternative to these methods is the application of thin, self‐adherent foil systems directly to the steel substrate. The corrosion protection performance of newly developed foil systems was tested for various combinations of foil materials and pressure‐sensitive adhesives (with and without corrosion inhibitors) and different surface preparation parameters by means of accelerated cyclic laboratory tests with simulated offshore conditions. The adhesion properties were determined by means of peel tests. The tests were designed, by means of statistical methods (design of experiments, analysis of variance). A foil system with the following factor combination was found to provide an optimum performance: Surface preparation grade: Sa 2½; roughness: Rz = 50–75 µm; abrasive material: high‐carbon steel grit; adhesive layer thickness: 200 g/m2; inhibitor material: calcium aluminum polyphosphate silicate hydrate; foil material: polyvinylchloride (160 µm) + poly(methyl methacrylate) (40 µm).

Effect of Strouhal number on propulsion of tandem flapping foils

Motivated by the energy efficient locomotion by flock of birds and school of fish to develop biomimetic systems, the current study studies the propulsive performance of the tandem configuration of two-foil system. The effects of the kinematic motion parameters such as heave and pitch amplitudes and flapping frequency on the propulsive performance of the tandem two-foil system is yet to be explored comprehensively due to the complex nature of the wake-foil interaction. Here, we numerically investigate these effects by utilizing a finite element based moving mesh framework to model the flapping foil motion subjected to fluid flow. The performance of the upstream foil is found to be similar to that of an isolated single foil. However, for the downstream foil, a beating phenomenon is observed in the thrust response when the flapping frequency is different for both the foils. This feature can help tune propulsive performance of the foil system. Furthermore, through a control volume analysis, we show that sole reliance on the time-averaged streamwise velocity may not yield correct trends for the mean thrust forces, which has been typically followed in the literature. Variation in the time-averaged pressure in the wake is significant in predicting correct thrust forces.

CFD Analysis of Interference Factor in Hydrofoil-Supported Catamarans (HYSUCAT)

Catamaran, with its distinctive dual-hull design, offers unique advantages in maritime applications, including improved stability and space utilization over traditional monohull vessels. However, the interaction between the two hulls generates complex hydrodynamic phenomena, significantly influencing the vessel's overall performance. One critical aspect of this interaction is the interference factor, which affects the hydrodynamic resistance encountered by the vessel. The purpose of this paper is to investigate the changes in hydrodynamic characteristics that occur when hydrofoils are incorporated into typical catamaran hull forms. This is accomplished through the utilization of advanced Computing Fluid Dynamics (CFD) simulations. In this study, a Delft-372 catamaran with a concept design is modified by installing a foil system with a high Reynolds number in order to reduce its overall resistance. The new system is then analyzed in order to determine the impact that it has on interference factors. For the purpose of achieving a comprehensive understanding of hydrodynamic behavior, the simulations are carried out under a variety of operating conditions, which include a variety of speeds. Simulations result indicate that the interference factor consistently increases drag for hydrofoil-supported catamarans to more than double that of monohulls across all speeds, particularly when hydrofoil-induced flow disturbances adversely affect the hull's boundary layer, leading to reduced efficiency.

Ship Performances CFD Analysis of Hydrofoil-Supported High-Speed Catamaran Hull Form

Fast ferries with efficient fuel use are becoming increasingly in demand as fossil fuels become more in short supply and metropolises expand all over the globe in coastal and estuarine environments. These criteria need to be fulfilled by the Hydrofoil Supported Catamaran (HYSUCAT). A catamaran with wings between its demi hulls is known as an HYSUCAT, and it combines the positive traits of both the catamaran (manoeuvrability, big deck area) and the wing in-ground vehicle (excellent lift-to-drag ratio). In this research, a concept design Delft-372 catamaran is refitted with a high Reynolds number foil system to lower its overall resistance. The numerical solution of the Reynolds-averaged Navier–Stokes (RANS) equations employing the k-w SST turbulence model is used to simulate the flow around a high-speed catamaran with a hydrofoil. According to the simulation findings, the hydrofoil-assisted catamaran was determined to be a viable alternative to the current catamaran. This is due to a significant decrease in the overall resistance of the ship, reaching up to 42%, as well as notable improvements in pitch angle, reaching up to 26%.

Experimental study of the resistance of a hydrofoil supported watercraft (hysuwac)

A possible alternative to reduce fuel consumption on a ship is through energy efficiency. For this purpose, a hydrofoil supported watercraft (hysuwac) utilizes two hydrofoils, one installed near the bow and the other near the stern of the catamaran, to reduce the vessel’s resistance. To investigate the effectiveness of the hydrofoils, CFD calculations were conducted in an earlier study. The purpose of this study is to provide experimental data to validate the CFD calculation results reported earlier for which towing tests were conducted at the Laboratory of Ship Hydrodynamics, ITS Surabaya, Indonesia. The ship model was made by using a three-dimensional print, which is then assembled into a ship model that meets the test requirements. The hydrofoil used has a NACA 641-212 section with an angle of attack of 4°. Twelve variations of towing tests were carried out with six variations of speed and two conditions, namely catamaran without and with foil system. A comparison between the CFD and experimental results shows that the CFD results are consistent with the experimental data. The minimum magnitude of percentage difference between the CFD results and experimental data is 1.14%, while the maximum magnitude of this is 16.79%. The observed difference is ascribed mainly to scale effects.

Alteration of cholesterol content and oxygen level in intestinal organoids after infection with Staphylococcus aureus.

The pathogenicity elicited by Staphylococcus (S.) aureus, one of the best-studied bacteria, in the intestine is not well understood. Recently, we demonstrated that S. aureus infection induces alterations in membrane composition that are associated with concomitant impairment of intestinal function. Here, we used two organoid models, induced pluripotent stem cell (iPSC)-derived intestinal organoids and colonic intestinal stem cell-derived intestinal organoids (colonoids), to examine how sterol metabolism and oxygen levels change in response to S. aureus infection. HPLC quantification showed differences in lipid homeostasis between infected and uninfected cells, characterized by a remarkable decrease in total cellular cholesterol. As the altered sterol metabolism is often due to oxidative stress response, we next examined intracellular and extracellular oxygen levels. Three different approaches to oxygen measurement were applied: (1) cell-penetrating nanoparticles to quantify intracellular oxygen content, (2) sensor plates to quantify extracellular oxygen content in the medium, and (3) a sensor foil system for oxygen distribution in organoid cultures. The data revealed significant intracellular and extracellular oxygen drop after infection in both intestinal organoid models as well as in Caco-2 cells, which even 48 h after elimination of extracellular bacteria, did not return to preinfection oxygen levels. In summary, we show alterations in sterol metabolism and intra- and extracellular hypoxia as a result of S. aureus infection. These results will help understand the cellular stress responses during sustained bacterial infections in the intestinal epithelium.

A Segmental 2D Readout Board Manufactured in Printed Circuit Board Technology for Gas Electron Multiplier Detectors.

The Gas Electron Multiplier (GEM) was introduced by Fabio Sauli in 1997. This technology is broadly used in current and planned High-Energy Physics (HEP) experiments. One of the key components of these detectors is a readout board, which collects charges amplified by GEM foils and transfers them to readout electronics. The commonly used Cartesian XY readout boards are manufactured from the same type of polyamide film used to produce the GEM foils. The manufacturing process utilizes a deep polyimide etching, similar to the Micro Chemical Vias (MCV) etching process, which is protected by patent. The material prepared in this way is glued onto a rigid substrate and mounted in a detector. The production process was developed at CERN, and the technology has been commercialized to a small extent. Consequently, only a few research centers have the ability to make dedicated readout strips readouts. GEM detectors are characterized by a segmented structure that allows the separation of an electron-multiplying structure from a readout. This feature enables the implementation of a new type of charge reading system without the need to interfere with the GEM foil system. A new approach is proposed to simplify production and reduce the costs of GEM detector readout boards. It is based on the concept of segmental readout structures that are manufactured in standard Printed Circuit Board (PCB) technology. The interconnectors and mountings are located on the back of the bottom, so it is possible to place the readout electronics behind the readout plate. The boards are designed in such a way that they can be panelized into a readout with a more extensive active area. The margin between PCBs is minimalized to approximately 200 µm, which is less than 1% of the 70 × 70 mm2 board area, so the active area is as big as possible. Therefore, this solution gives us the ability to further increase the size of a readout by adding additional segments, which reduces the cost of scaling up the detector size. A few research groups have suggested similar solutions that utilize PCB technology, but currently, only detectors with 1D zigzag readouts have been validated and used. The measurement results of other 2D (XY) redouts using PCB technology have not been presented. The measurements shown and discussed in this paper validated the proposed technology. X-ray radiographs were obtained, validating the ability to use this technology to manufacture readout boards for GEM detectors. In opposition to state-of-the-art readouts, the proposed solution can be manufactured by any PCB manufacturer without using MCV-patented technology. This gives the users flexibility in designing and ordering low-cost custom readouts.

Numerical analysis of wake wash reduction for catamaran with hydrofoils

Catamarans are popular for fast sea transportation because of their high potential of speed and stability. However, the wake wash generated by catamarans often interfere surrounding environment. For the prevention of large waves generated by catamarans, a stern hydrofoil is known to be one of the effective devices. In the present study, the effect of hydrofoil attached at the stern of a catamaran for the wake wash reduction is investigated using CFD. The various configurations of a stern hydrofoil are designed and their performance are examined with respect to resistance in calm water and wave amplitudes. The computational domain is taken large enough to be able to analyze the wave field far downstream. In addition to the bare hull and the hull with foil cases, the bare hull cases with the attitudes fixed to those of the cases with the foil are simulated for the detailed analysis of foil effects. The inter-comparison of these cases makes it possible to separate the foil effects into the hull attitude change effect and the foil-generated wave effect. The wake wash reduction by stern foil system is achieved with the appropriate combination of hull attitude change and the interaction of hull waves and foil waves. Finally the design directions of a stern hydrofoil for the wake wash reduction are suggested.

Самостабилизирующийся лопастной движитель

Object and purpose of research. The solution discussed in this paper is applicable to the propellers (including those with oscillating blades) operating in fluids, and is intended to ensure self-adjustment of blades to the optimal attack angle. Subject matter and methods. Blade self-adjustment to the optimal attack angle was achieved through one of the properties of the boundary layer for viscous flow around the foil system: this layer acquires different thickness at the opposite sides of foils with non-zero installation angle, thus becoming an asymmetric displacement body. The propeller intended to use this property had its blade and a stabilizing foil attached to a common axe so that the rotation axis of both the blade and the foil was between the application points of the hydrodynamic resultant force (i.e. centers of pressure) for the blade with and without the stabilizing foil. The locations of pressure centers were calculated as per the linear theory. This property of the propulsion system was confirmed experimentally. Main results. It was experimentally demonstrated that proper selection of the rotation axis coordinate in a viscous fluid creates a zone of stable attack angles. This zone also exists for symmetric foils arranged one after another with non-zero installation angle. It means that these foils could be used in a fin-type propulsor, but this will require a control device preventing blade lock due to reversal of oscillation direction. In the suggested solution, blade axis is connected with driving rods by means of steering arms, and the driving rods themselves have guides locking blade tips when oscillation direction changes. Conclusion. The solution suggested in this paper has been experimentally validated, and it paves way to introduction of simple but efficient fin-type propulsors. Following this design, the author suggests a flipper with increased propulsion efficiency in a wide range of speeds, as well as a propulsor based on hinged hydrofoils: this design does not need propeller to maintain the speed.

Installation and commissioning of the stripping foil system in the new CERN PS booster 160 MeV H− injection region

During Long Shutdown 2 (LS2) at CERN, the new Linac4 (L4) accelerator was connected to the PS Booster (PSB) to inject 160 MeV H− beam into the 4 superposed PSB rings. In order to achieve this, a completely new H− charge-exchange injection chicane system, with 200 µg/cm2 carbon stripping foil units, to convert the negative hydrogen ions into protons, by stripping off the electrons, has been installed. Beam commissioning of this system started in December 2020 and different types of foils have been used for this purpose. In parallel, stripping efficiency measurements, of different foil types, continued to take place with the stripping foil test stand in the L4 Transfer Line. This paper briefly recalls the final design, and installation of, the main components in the PSB injection region, before reporting on the important results obtained during measurements and commissioning with beam.

Sound generated by flow over two traveling wavy foils in a side-by-side arrangement

Numerical simulations are employed to investigate the sound generated by flow over two traveling wavy foils in a side-by-side arrangement by an immersed-boundary-method-based hybrid approach. The effects of Strouhal number (St), phase difference, and lateral spacing (S) between the foils on the flow performance and the sound pressure field are examined. The results imply that the sound produced by a single foil is dominated by the lift dipole, and that the low-amplitude–high-frequency foil can achieve higher thrust and higher sound pressure compared to the high-amplitude–low-frequency foil. For the two side-by-side foils (i.e., an in-phase and anti-phase foil system), the sound pressure fields exhibit distinct features. Specifically, a dipole-like pattern appears during in-phase motion, whereas a monopole-like pattern exists during anti-phase motion. Moreover, the magnitude of the sound pressure increases slightly with increasing S in the in-phase case. However, the sound pressure decreases rapidly when S < 0.7L (foil length) and then remains nearly unchanged when S > 0.7L in the anti-phase case. Furthermore, the anti-phase foil system could improve thrust by increasing power consumption and could generate lower sound pressure compared to the in-phase one due to the distinct differences in wake patterns. The present work is expected to improve the understanding of sound-generation mechanisms of fish-like locomotion and collective motion for relevant biomimetic underwater vehicles.

Phased plan for the implementation of the time-resolving magnetic recoil spectrometer on the National Ignition Facility (NIF).

The time-resolving magnetic recoil spectrometer (MRSt) is a transformative diagnostic that will be used to measure the time-resolved neutron spectrum from an inertial confinement fusion implosion at the National Ignition Facility (NIF). It uses a CD foil on the outside of the hohlraum to convert fusion neutrons to recoil deuterons. An ion-optical system positioned outside the NIF target chamber energy-disperses and focuses forward-scattered deuterons. A pulse-dilation drift tube (PDDT) subsequently dilates, un-skews, and detects the signal. While the foil and ion-optical system have been designed, the PDDT requires more development before it can be implemented. Therefore, a phased plan is presented that first uses the foil and ion-optical systems with detectors that can be implemented immediately-namely CR-39 and hDISC streak cameras. These detectors will allow the MRSt to be commissioned in an intermediate stage and begin collecting data on a reduced timescale, while the PDDT is developed in parallel. A CR-39 detector will be used in phase 1 for the measurement of the time-integrated neutron spectra with excellent energy-resolution, necessary for the energy calibration of the system. Streak cameras will be used in phase 2 for measurement of the time-resolved spectrum with limited spectral coverage, which is sufficient to diagnose the time-resolved ion temperature. Simulations are presented that predict the performance of the streak camera detector, indicating that it will achieve excellent burn history measurements at current yields, and good time-resolved ion-temperature measurements at yields above 3 × 1017. The PDDT will be used for optimal efficiency and resolution in phase 3.

Resistance Analysis of a Hydrofoil Supported Watercraft (Hysuwac): A Case Study

Energy efficiency and environmental sustainability are important aspects in ship design and operation. Hull-shape optimization, hull cleaning and coating, and the use of appendages are, among others, well-known efforts to reduce ship fuel consumption. Regarding energy efficiency and environmental sustainability, it is possible to effectively reduce the resistance of an existing catamaran by retrofitting a foil system to it. In this study, a foil system is designed and retrofitted to a catamaran to reduce its total resistance. Reynolds-averaged Navier-Stokes simulations, utilizing k-w SST turbulence model, were performed to study the effects of the foil system on the vessel’s total resistance. Free surface effects were modelled, i.e., the generation of waves due to the vessel’s movement on the water surface. The foil system affects the wetted surface area, running sinkage and trim, and the wave pattern generated by the vessel, which ultimately affect the vessel’s total resistance. At relatively low speeds (Fr < 0.7), an increase of the total resistance, reaching a value of approximately 11%, was observed due to the foil system. However, at higher speeds (Fr > 0.7), the foil system decreases the total resistance, reaching a value of approximately 32% at the service speed (Fr = 1.24). The 32% resistance reduction at the service speed is promising in view of the intended purpose of the foil system as an energy saving device.

Propulsive performance and vortex wakes of multiple tandem foils pitching in-line

Numerical studies are presented on the propulsive performance and vortex dynamics of multiple hydrofoils pitching in an in-line configuration. The study is motivated by the quest to understand the hydrodynamics of multiple fin–fin interactions in fish swimming. Using the flow conditions (Strouhal and Reynolds numbers) obtained from a solitary pitching foil of zero net thrust, the effect of phase differences between neighboring foils on the hydrodynamic performance is examined both in position-fixed two- and three-foil systems at Reynolds number Re=500. It is found that the three-foil system achieves a thrust enhancement up to 118% and an efficiency enhancement up to 115% compared to the two-foil system. Correspondingly, the leading-edge vortex (LEV) and the trailing-edge vortex (TEV) of the hindmost foil combine to form a ‘2P’ wake structure behind the three-foil system with the optimal phase differences instead of a ‘2S’ wake, a coherent wake pattern observed behind the optimal two-foil system. The finding suggests that a position-fixed three-foil system can generate a ‘2P’ wake to achieve the maximum thrust production and propulsive efficiency simultaneously by deliberately choosing the undulatory phase for each foil. When increasing Reynolds number to 1000, though the maximum thrust and propulsive efficiency are not achieved simultaneously, the most efficient case still produces more thrust than most of the other cases. Besides, the study on the effects of three-dimensionality shows that when the foils have a larger aspect ratio, the three-foil system has a better hydrodynamic performance, and it follows a similar trend as the two-dimensional (2D) foil system. This work aids in the future design of high-performance underwater vehicles with multiple controlled propulsion elements.

A Novel Lithium Foil Cosmic-Ray Neutron Detector for Measuring Field-Scale Soil Moisture

During the past decade, cosmic-ray neutron sensing technology has enabled researchers to reveal soil moisture spatial patterns and to estimate landscape-average soil moisture for hydrological and agricultural applications. However, reliance on rare materials such as helium-3 increases the cost of cosmic-ray neutron probes (CRNPs) and limits the adoption of this unique technology beyond the realm of academic research. In this study, we evaluated a novel lower cost CRNP based on moderated ultra-thin lithium-6 foil (Li foil system) technology against a commercially-available CRNP based on BF3 (boron trifluoride, BF-3 system). The study was conducted in a cropped field located in the Konza Prairie Biological Station near Manhattan, Kansas, USA (325 m a.s.l.) from 10 April 2020 to 18 June 2020. During this period the mean atmospheric pressure was 977 kPa, the mean air relative humidity was 70%, and the average volumetric soil water content was 0.277 m3 m−3. Raw fast neutron counts were corrected for atmospheric pressure, atmospheric water vapor, and incoming neutron flux. Calibration of the CRNPs was conducted using four intensive field surveys (n > 120), in combination with continuous observations from an existing array of in situ soil moisture sensors. The time series of uncorrected neutron counts of the Li foil system was highly correlated (r2 = 0.91) to that of the BF-3 system. The Li foil system had an average of 2,250 corrected neutron counts per hour with an uncertainty of 2.25%, values that are specific to the instrument size, detector configuration, and atmospheric conditions. The estimated volumetric water content from the Li foil system had a mean absolute difference of 0.022 m3 m−3 compared to the value from the array of in situ sensors. The new Li foil detector offers a promising lower cost alternative to existing cosmic-ray neutron detection devices used for hectometer-scale soil moisture monitoring.

Seakeeping Analysis of a Hydrofoil Supported Watercraft (Hysuwac): A Case Study

Considering recent global temperature increase and observed climate change, efforts have been made towards energy efficiency and reduction of green-house gas emission. A foil system is proposed in this study and retrofitted to an existing catamaran to reduce the energy use and to improve the vessel’s seakeeping characteristics. The objective of this study is to investigate the effects of the application of the foil system on the seakeeping performance of the vessel. CFD simulations based on a panel method were carried out to obtain the seakeeping characteristics of the catamaran with and without foil system. Simulation results show that the foil system reduced the vessel motions in a seaway: the heave-, pitch- and roll significant amplitudes were reduced 4.41, 9.97 and 3.30 percent, respectively, due to the application of the foil system. In addition, the vertical accelerations at the fore perpendicular (FP) and at deck were reduced 3.66 and 9.70 percent, respectively. A check against the NORDFORSK criteria for fast small crafts shows that the vessel can operate safely up to sea state 2.

Synthesis of uniform nanometer-thick graphite film on polycrystalline Ni substrate with ultrafine grains

When a polycrystalline Ni foil is used as the substrate for the chemical vapor deposition synthesis of multilayer-graphene or nanometer-thick graphite films (NGFs), these films always exhibit uneven morphologies and qualities on Ni grains with different orientations. In this study, we fabricated a carbon-supersaturated Ni foil (ss-Ni foil) to function as a carbon source through an ultrafast cooling process (∼180 °C/s), while an additional Ni film was sputtered on the ss-Ni foil to act as a buffer layer and a new surface for NGF growth. By re-annealing the Ni film/ss-Ni foil system at a low temperature (∼650–800 °C) within a short duration, NGF can rapidly form on the Ni film owing to the high supersaturation degree of the ss-Ni foil. The grain growth of the Ni film is limited by the low-temperature growth process, and the ultrafine grains of Ni film averaged the grain orientation effect from the Ni foil. The NGF formed on the Ni film/ss-Ni foil showed a significant improvement in thickness and quality uniformity, and we studied the influences of Ni film thickness as well as re-annealing temperature and time on the diffusion of carbon in the Ni film/ss-Ni foil system and summarized the growth mechanism.

Flow-energy harvesting using a fully passive flapping foil: A guideline on design and operation

Following our previous work [Int. J. Mech. Sci. (2020), vol. 177, 105587], we searched the best power extraction performance of a novel flow-energy harvester, which utilizes a fully passive flapping foil to extract energy from air/water flows. A series of water-tunnel experiments were conducted on the same test model at the Reynolds number around 105. Through investigating the effects of two unexplored key parameters, a higher overall maximum power conversion efficiency of 42.7% was obtained at water speed 0.71 m/s and foil pitching amplitude 60∘, corresponding to a larger mean power output of about 1.51 W. A quasi-steady theoretical model was also developed to fast predict the system performance in a larger parameter space. It was found that, in addition to typical dynamics, i.e., a flapping cycle includes two pure-heaving phases and two stroke-reversal phases, the foil system can also continuously operate in a “no-pure-heaving” zone where a flapping cycle only includes two successive stroke-reversal phases. Through these experimental and theoretical studies, a useful guideline was proposed on the design and operation of the foil system.

Underwater Walking Mechanism of Underwater Amphibious Robot Using Hinged Multi-modal Paddle

This study proposes an underwater walking mechanism for an underwater amphibious robot that is propelled by a degree of freedom flapping foil system. To implement stable walking in water, we proposed a distinctive hinged multi-modal paddle and developed an underwater amphibious robot. For the proposed paddle, forward walking model is proposed regarding both the ground contact and hydrodynamic forces in each walking phase: the stance and swing phases. Then, we generalized dynamic equations of motion for the amphibious robot based on the forward walking model. The proposed mechanism and robot were evaluated through thrust and forward walking tests in an indoor water tank. The results of the forward walking test exhibited a highly accurate trajectory of legged locomotion compared to the model-based simulation results. Moreover, field tests on gravel and soft terrains of a seabed, revealed that the proposed system allowed the amphibious robot to walk qualitatively.