Foil Systems Research Articles

The propulsion performance of the semi-active tandem flapping foils for wave gliders: A study on vortex interactions and hydrodynamic performance

An investigation is conducted on the propulsion performance of semi-active flapping foils in tandem configuration of the wave glider, considering different vortex effects and tandem distances. The Finite Volume Method is utilized with commercial CFD software Fluent to solve the URANS equations around the flapping foil. A mesh comprising a 2D NACA0012 foil with Reynolds number Re = 42,000 is used in all simulations. The study investigates the propulsion performance of tandem flapping foil systems, focusing on the differing impacts of wave interaction on the front and rear foils. It explores how varying tandem distances and reduced frequencies influence thrust enhancement and degradation. The research reveals that while the front foil consistently benefits from thrust enhancement, the rear foil's performance is more complex, being subject to thrust enhancement or reduction due to wake vortex interactions. Detailed analyses of instantaneous thrust coefficients, pitching trajectories, and pressure contours provide insights into the hydrodynamic performance of these systems. The findings emphasize the importance of synchronization in motion between the foils for optimal propulsion and highlight the rear foil's susceptibility to changes in the wake flow, affecting its thrust generation capability. Thus, the optimal tandem distance can fully capitalize on the thrust enhancement effect of the wake interaction to improve the performance of the tandem flapping foil propulsion system.

A resistance model for hydrofoil fast ferries with fully submerged foil systems

This paper introduces an algorithmic method for the design and resistance prediction of hydrofoil vessels for fast ferry applications, using only design speed and mass as input parameters. A database of resistance estimates has been created and shared online. Furthermore, a simple model is introduced for the extension of the results to off-design speeds.The efficacy of the models is demonstrated through three case studies. Firstly, the importance of accounting for the power requirement during take-off is investigated, concluding that a simple assumption of constant speed yields accurate energy estimates for routes exceeding approximately six nautical miles.Case study number two entails a comparative analysis of hydrofoil vessel resistance to that of slender catamarans across a wide range of vessel sizes and speeds. The results reveal a potential for reducing the energy requirement of passenger fast ferries by 30% to 50% through the use of hydrofoils.The paper concludes with an investigation into the influence of surface roughness on hydrofoil resistance, indicating significant deteriorating effects even at moderate roughness levels.

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).

Number of occlusal contacts during maximum intercuspation in dentate adults: A systematised review.

Evaluating occlusal contacts during maximum intercuspation is one of the requirements for guiding clinicians during occlusal corrections and has been a topic of considerable importance for researchers over many decades. This systematised review intends to evaluate the average number of occlusal contacts present in dentate adults, as documented within the dental literature over the past four decades (1980s-2022). Electronic searches were conducted in three databases (PubMed, Livivo and Ovid) using a combination of search words. A total of 651 records were identified through PubMed and another 37 records through Livivo and Ovid databases. After eliminating duplicates and irrelevant records, 168 records were screened. Full texts of 61 articles remained, out of which 18 relevant papers that presented occlusal contacts in quantifiable value were considered. Various occlusal indicators, such as articulating paper, wax sheets, shimstock foil, impression material, gnathodynamometers and digital occlusal analysis systems, were used to evaluate occlusal contacts. The number of occlusal contacts widely ranged from 11 to 70. These variations likely depends upon the type and technique of occlusal indicator used, diversity among sampled populations and differing data collection procedures. Different methods of identifying occlusal contacts in the intercuspal position yield different numbers and patterns of contacts, depending on the nature and physical properties of the indicators used.

Влияние числа лопастей на высокочастотный шум судового движителя

Object and purpose of research. This paper discusses blade systems of propellers and water jets. The purpose of the study was to outline the ways to mitigation of high-frequency non-cavitation noise of marine propulsors. Subject matter and methods. The study analyses Russian and foreign publications on aero- and hydroacoustics of propellers and foil systems. It also determines the parameters of turbulent boundary layer on propeller blades with respect to its effect upon propeller noise radiation. Noise assessment methods obtained for aerodynamics of foil systems have been applied to marine propulsors. Main results. Theoretical studies have shown that marine propellers with fewer blades tend to have lower radiation of high-frequency noise. Direct noise measurements of propulsor models performed under this study have confirmed this trend. Conclusion. In contrast to the low-frequency propeller noise, high-frequency acoustic radiation can be achieved through reduction of propeller blade number.

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.

Fractal dimensions of blast-cleaned steel surfaces and their effects on the adhesion of polymeric foil systems with integrated pressure-sensitive adhesives

Morphology and structure of substrate surfaces are crucial parameters for the establishment of reliable protective layers as they determine the adhesion of the protective layer to the substrate. Insufficient adhesion will promote unwanted effects, namely delamination and blistering. This applies as well to protective hybrid-layers, consisting of a polymeric foil bonded to the substrate (usually steel) by means of an integrated pressure-sensitive adhesive. Numerous parameters are known to characterize the morphology of metal substrates. In this study, mild steel samples were prepared using dry-blast cleaning with abrasive materials (metallic, minerals) of different particle shapes and particle sizes to investigate the impact of surface profile parameters on the adhesion of polymeric foil systems (PFS). For this purpose, 2D profiles were taken from a total of 12 surface configurations with a digital contact profilometer. Fractal dimensions were estimated based on these recorded profiles using the box-counting method. For comparison, conventional roughness parameters were measured as well. Tests with a pull-off strength testing device were performed on the applied PFS to quantify its adhesion to the substrates. The estimated pull-off tensile strength values were correlated with the estimated fractal dimensions. Design of Experiment (DoE) was applied to the test design in order to establish statistically sound relationships. Using a linear correlation model, it could be shown that fractal dimensions were suitable for quantifying the adhesion with a significantly higher accuracy than commonly used substrate (roughness) parameters.

Simple Black-Box Universal Adversarial Attacks on Deep Neural Networks for Medical Image Classification

Universal adversarial attacks, which hinder most deep neural network (DNN) tasks using only a single perturbation called universal adversarial perturbation (UAP), are a realistic security threat to the practical application of a DNN for medical imaging. Given that computer-based systems are generally operated under a black-box condition in which only input queries are allowed and outputs are accessible, the impact of UAPs seems to be limited because well-used algorithms for generating UAPs are limited to white-box conditions in which adversaries can access model parameters. Nevertheless, we propose a method for generating UAPs using a simple hill-climbing search based only on DNN outputs to demonstrate that UAPs are easily generatable using a relatively small dataset under black-box conditions with representative DNN-based medical image classifications. Black-box UAPs can be used to conduct both nontargeted and targeted attacks. Overall, the black-box UAPs showed high attack success rates (40–90%). The vulnerability of the black-box UAPs was observed in several model architectures. The results indicate that adversaries can also generate UAPs through a simple procedure under the black-box condition to foil or control diagnostic medical imaging systems based on DNNs, and that UAPs are a more serious security threat.

Fish-like three-dimensional swimming with an autonomous, multi-fin, and biomimetic robot

Fish migrate across considerable distances and exhibit remarkable agility to avoid predators and feed. Fish swimming performance and maneuverability remain unparalleled when compared to robotic systems, partly because previous work has focused on robots and flapping foil systems that are either big and complex, or tethered to external actuators and power sources. By contrast, we present a robot—the Finbot—that combines high degrees of autonomy, maneuverability, and biomimicry with miniature size (160 cm3). Thus, it is well-suited for controlled three-dimensional experiments on fish swimming in confined laboratory test beds. Finbot uses four independently controllable fins and sensory feedback for precise closed-loop underwater locomotion. Different caudal fins can be attached magnetically to reconfigure Finbot for swimming at top speed (122 mm s−1 ≡ 1 BL s−1) or minimal cost of transport (CoT = 8.2) at Strouhal numbers as low as 0.53. We conducted more than 150 experiments with 12 different caudal fins to measure three key characteristics of swimming fish: (i) linear speed-frequency relationships, (ii) U-shaped CoT, and (iii) reverse Kármán wakes (visualized with particle image velocimetry). More fish-like wakes appeared where the CoT was low. By replicating autonomous multi-fin fish-like swimming, Finbot narrows the gap between fish and fish-like robots and can address open questions in aquatic locomotion, such as optimized propulsion for new fish robots, or the hydrodynamic principles governing the energy savings in fish schools.

Dual flapping foil system for propulsion and harnessing wave energy: A 2D parametric study for unaligned foil configurations

Dual flapping foil systems are a promising concept able to improve overall ship propulsion performance and recover wave energy, reducing fuel consumption and making maritime equipment eco-friendlier.In this context, the present article aims to present a 2D parametric study of a flapping foil system able to operate in two modes: energy harnessing and propulsion. First, a brief theoretical review is presented, followed by the numerical approach used and the validation tests performed.The main goal of the parametric study is to analyse how the out-of-phase configuration and the spacing inter-foils influence the results in terms of hydrodynamic coefficients and power output, when compared to the baseline (foils aligned).Implementing the cases using the κ−ω SST turbulence model, combined with the overset 6DOF approach for the foil motion from the commercial CFD tool ANSYS® Fluent®, it was possible to show that cases 1 & 2 (unaligned, spaced configuration) presented a better overall performance for the two operation modes.

3-Path SiGe BiCMOS power amplifier on thinned substrate for IoT applications

This paper reports a transformer-based integrated class-A Differential Power Amplifier (DPA) for the Internet of Things (IoT) applications. The proposed 5–6 GHz fully integrated differential PA is fabricated in a cost-effective 95 GHz-fmax, 0.25 μm SiGe BiCMOS technology (IHP process SGB25V). The amplifier utilizes a thin Si chip with a thickness of 45 μm in order to be embedded into flexible electronic foil systems. Several key RF performance parameters of the DPA with different substrate thicknesses are evaluated at the wafer level. The measurement results indicate that the DPA shows no significant S-parameters degradation due to the thickness differences. The measured gain center frequency is shifted about 300 MHz towards higher frequencies after thinning because of the image mirror currents within the conducting material at the backside of the chip. The DPA achieves 10.65 dB and 9.7 dB small-signal gain at 5.5 GHz before and after thinning, respectively. The PA delivers an output power of +9 dBm before and +8.1 dBm after thinning process at Pin = −1.3 dBm. The simulated 1 dB compression point occurs at +10.76 dBm output power with a PAE of 15%.

On the Interfoil Spacing and Phase Lag of Tandem Flapping Foil Propulsors

The aim of this article is to provide a theoretical basis upon which to advance and deploy novel tandem flapping foil systems for efficient marine propulsion. We put forth three key insights into tandem flapping foil hydrodynamics related to their choreography, propulsive efficiency, and unsteady loading. In particular, we propose that the performance of the aft foil depends on a new nondimensional number, s/Uτ, which is the interfoil separation s normalized by the distance that the freestream U advects in one flapping period, τ. Additionally, we show how unsteady loading can be mitigated through choice of phase lag. 1. Introduction Marine propulsion has been an important engineering problem since the time of Archimedes (287–212 BC) (Carlton 1994). The evolution of propulsor design from the classic Archimedes screw to the modern screw propeller has primarily been driven by considerations of efficiency. A hydrodynamically efficient propulsor has low friction losses, low turbulent losses, an ability to manipulate incident vorticity, and a stable and persistent jet-type wake. it is composed of lifting surfaces with high aspect ratio and large lift-to-drag ratio. Although screw propellers offer advantages with regard to mechanical simplicity (just need to turn the shaft!), they have practical limitations that place upper bounds on the overall hydrodynamic efficiency, such as the limitations of aspect ratio due to cavitation at high tip speeds. Research with isolated flapping foils has demonstrated up to 87% propulsive efficiency (Anderson et al. 1998), nearly achieving the ideal efficiency of an actuator disk. However, single-foil propulsion is not practical due to shortcomings, such as large oscillations in thrust, large unsteady side forces, and no mechanical redundancy. Many other nontraditional propulsors also suffer these flaws or are simply inefficient. Biomimetic concept designs and trade-offs have recently been reviewed by Fish (2013). One promising nontraditional propulsor concept involves in-line tandem flapping foils (two hydrofoils, one aft of the other). Recent research indicates that the high efficiency of a single flapping foil may be possible with a tandem foil arrangement (Akhtar et al. 2007; Boschitsch et al. 2014). Tandem flapping foils may also solve the operational problems associated with a single foil, such as inconsistent thrust and side force.

On the Interfoil Spacing and Phase Lag of Tandem Flapping Foil Propulsors

The aim of this article is to provide a theoretical basis upon which to advance and deploy novel tandem flapping foil systems for efficient marine propulsion. We put forth three key insights into tandem flapping foil hydrodynamics related to their choreography, propulsive efficiency, and unsteady loading. In particular, we propose that the performance of the aft foil depends on a new nondimensional number, s/Utau, which is the inter-foil separation s normalized by the distance that the freestream U advects in one flapping period tau. Additionally, we show how unsteady loading can be mitigated through choice of phase lag.

Sustainability – The Art of Modern Architecture

Over the last 10-15 of years the building industry has been faced with an increasing demand for sustainable solutions. According to Peter Bakker, president and CEO of the World Business Council for Sustainable Development WBCSD, buildings are the largest energy consumers in the world economy, accounting for over one-third of final energy use and approximately 30% of global carbon emissions [1]. These figures do not take into account the energy and carbon emissions due to production of building materials or for logistics and building construction. The demand for both energy and resources is soaring as global construction booms, especially in countries such as China and India. This means that developments in building practice can significantly contribute to tackling climate change and energy use. The use of ETFE foils as a new transparent material substitute for glass provides the potential for not only vast savings in material quantities but simultaneously makes possible a new type of space for living and working. The environmental benefits are presented as results of a comparative study between glass and ETFE solutions on two projects in Germany, Domaquarée in Berlin and Kapuzinergraben in Aachen, based on a life cycle analysis. The social benefits will be presented using the example of Kingsdale School in London and Kuwait Avenues, Kuwait. It will be shown that the introduction of ETFE foil systems in modern architecture will significantly contribute not only to environmental sustainability, but also create economic and social advantages compared to more classic building materials.

Effects of time-varying camber deformation on flapping foil propulsion and power extraction

Research into the effectiveness of flapping foil propulsion and power extraction systems has typically focused on the kinematic parameters defining the pitching and plunging motion, and used simple basic rigid airfoil shapes. In this paper, the effects of a time-varying deformable foil shape on the power extraction and propulsive efficiency of flapping foil systems are studied. Two-dimensional Navier–Stokes solutions using the commercial flow solver Fluent are performed with a deformable mesh to alter the camber of the foil during the flapping cycle. All simulations are assumed to be fully laminar, with a free stream Reynolds number of Re=1100 for the power extraction cases and Re=20000 for the propulsion cases, chosen to match representative cases in the existing literature. The shape of the foil is constructed by deforming the camber line via a circular arc centered at the mid-span, with the magnitude of the circular arc deformation varying sinusoidally in time. The phase angle of this sinusoidal camber variation is the primary independent variable, resulting in a broad range of foil interactions with the shed vortex flow fields as the shape varies over the flapping cycle. This camber deformation is superimposed on kinematically constrained sinusoidal motions for both the power extraction and propulsion regimes, as well as semi-passive motions for power extraction. The results show that the efficiency of these systems can be increased by judiciously deforming the foil shape to interact with the resulting leading and trailing edge vortex structures. For all cases, the power required to deform the foil surface is included in the overall efficiency calculation, and for several cases is a significant factor in the final efficiency. The performance of the power extraction cases is primarily determined by the interactions between the shed LEV and the foil horizontal surface during the plunging stroke and the interaction of the trailing edge as it passes through the vortex during the pitch reversal portion of the cycle. The semi-passive cases for power extraction are also strongly affected by the vortex interactions, and the resulting forces and moments can significantly alter the flapping frequency, further increasing their impact. The propulsion cases show a high dependence on the interaction of the leading edge vortex with the foil curvature to provide high leading suction and greater propulsive forces. For all three regimes, regions of phase angle where the efficiency is increased by the deformation of the foil are shown.

Real-time simulator for designing electron dual scattering foil systems.

The purpose of this work was to develop a user friendly, accurate, real‐time computer simulator to facilitate the design of dual foil scattering systems for electron beams on radiotherapy accelerators. The simulator allows for a relatively quick, initial design that can be refined and verified with subsequent Monte Carlo (MC) calculations and measurements. The simulator also is a powerful educational tool. The simulator consists of an analytical algorithm for calculating electron fluence and X‐ray dose and a graphical user interface (GUI) C++ program. The algorithm predicts electron fluence using Fermi‐Eyges multiple Coulomb scattering theory with the reduced Gaussian formalism for scattering powers. The simulator also estimates central‐axis and off‐axis X‐ray dose arising from the dual foil system. Once the geometry of the accelerator is specified, the simulator allows the user to continuously vary primary scattering foil material and thickness, secondary scattering foil material and Gaussian shape (thickness and sigma), and beam energy. The off‐axis electron relative fluence or total dose profile and central‐axis X‐ray dose contamination are computed and displayed in real time. The simulator was validated by comparison of off‐axis electron relative fluence and X‐ray percent dose profiles with those calculated using EGSnrc MC. Over the energy range 7–20 MeV, using present foils on an Elekta radiotherapy accelerator, the simulator was able to reproduce MC profiles to within 2% out to 20 cm from the central axis. The central‐axis X‐ray percent dose predictions matched measured data to within 0.5%. The calculation time was approximately 100 ms using a single Intel 2.93 GHz processor, which allows for real‐time variation of foil geometrical parameters using slider bars. This work demonstrates how the user‐friendly GUI and real‐time nature of the simulator make it an effective educational tool for gaining a better understanding of the effects that various system parameters have on a relative dose profile. This work also demonstrates a method for using the simulator as a design tool for creating custom dual scattering foil systems in the clinical range of beam energies (6–20 MeV).PACS number: 87.10.Ca

In vitro model to proof the efficacy of 2 foil drainage systems for abdominal negative pressure therapy

Abstract The negative pressure therapy (NPT) is used as a method of treatment of open abdomen based on high fluid retention in the abdominal cavity based on infection and/or abdominal hypertension. Thereby, different foil systems are used to remove the fluid of the abdomen. Two foils, system 1 (Suprasorb® CNP) and system 2 (AB-Thera®), two of the commercial abdominal negative pressure systems, were compared in an in vitro model with their abdominal fluid permeability. We compared both foils with respect to their permeability under the same predefined conditions with the help of a self-developed system with a commercially available sub-pressure pump. System 2 original foil system did not show any measureable flow. System 1 showed a highly significant, higher permeability than the single layer of system 2. This supports the hypothesis that system 2 works in terms of an “overflow system”.

From Ceramics to Ceramic Steel: Genesis

Ceramics were introduced in dentistry since the 16th century as dental porcelain, primarily for the manufacture of porcelain teeth. Improved technology saw porcelain jacket crowns, metal ceramic systems with better bonding techniques of different alloys to porcelain, bonded foil systems and then the

SU-E-T-25: Real Time Simulator for Designing Electron Dual Scattering Foil Systems.

To create a user friendly, accurate, real time computer simulator to facilitate the design of dual foil scattering systems for electron beams on radiotherapy accelerators. The simulator should allow for a relatively quick, initial design that can be refined and verified with subsequent Monte Carlo (MC) calculations and measurements. The simulator consists of an analytical algorithm for calculating electron fluence and a graphical user interface (GUI) C++ program. The algorithm predicts electron fluence using Fermi-Eyges multiple Coulomb scattering theory with a refined Moliere formalism for scattering powers. The simulator also estimates central-axis x-ray dose contamination from the dual foil system. Once the geometry of the beamline is specified, the simulator allows the user to continuously vary primary scattering foil material and thickness, secondary scattering foil material and Gaussian shape (thickness and sigma), and beam energy. The beam profile and x-ray contamination are displayed in real time. The simulator was tuned by comparison of off-axis electron fluence profiles with those calculated using EGSnrc MC. Over the energy range 7-20 MeV and using present foils on the Elekta radiotherapy accelerator, the simulator profiles agreed to within 2% of MC profiles from within 20 cm of the central axis. The x-ray contamination predictions matched measured data to within 0.6%. The calculation time was approximately 100 ms using a single processor, which allows for real-time variation of foil parameters using sliding bars. A real time dual scattering foil system simulator has been developed. The tool has been useful in a project to redesign an electron dual scattering foil system for one of our radiotherapy accelerators. The simulator has also been useful as an instructional tool for our medical physics graduate students.

TECHNOLOGY VERSUS AGRO-ECOLOGY IN DESIGNING VEGETABLE PRODUCTION SYSTEMS IN THE NETHERLANDS

ISHS IV International Symposium on Ecologically Sound Fertilization Strategies for Field Vegetable Production TECHNOLOGY VERSUS AGRO-ECOLOGY IN DESIGNING VEGETABLE PRODUCTION SYSTEMS IN THE NETHERLANDS