Fabrication and characterization of folded foils supporting streamwise traveling waves

Proceedings of the 13th International Congress on Sound and Vibration, Vienna, Austria, 2006

ABSTRACT: The present paper reports the results of the first experimental observation of the wave-like aquatic propulsion suitable for man-inhabited marine vessels. The idea of this propulsion, first published by one of the present authors (V.V.K.) more than 10 years ago, is based on employing localised flexural elastic waves propagating along edges of wedge-like elastic structures. Such wave-supporting structures can be attached to a body of a small ship or a submarine as keels or wings and used for the propulsion. To verify the idea experimentally, the first working prototype of a small catamaran using the above-mentioned wave-like propulsion via the attached rubber keel has been build and tested. The test results have shown that the catamaran was propelled quite efficiently and could achieve the speed of about 36 cm/s, i.e. approximately one length of the vessel per second. The reported proof of the viability of the idea of wave-like propulsion as alternative to a propeller may open new opportunities for marine propulsion which can have far reaching implications.

Journal of Aircraft, 2010

A novel, bi-directional variable camber airfoil design employing a type of piezoceramic composite actuator known as Macro-Fiber Composite (MFC) is presented. From a broader perspective, the study aims to understand the behavior of solid-state aerodynamic force generation in high dynamic pressure airflow. The novel airfoil employs two active surfaces and a single four-bar (box) mechanism as the internal structure. The airfoil produces deflection in both directions from a flat camber line. The paper focuses on actuation modeling and response characterization under aerodynamic loads. A parametric study of aerodynamic response is employed to optimize kinematic parameters of the airfoil. The concept is fabricated implementing eight MFC 8557-P1 type actuators in a bimorph configuration to construct the active surfaces. The box mechanism generates deflection and camber change as predicted. Wind tunnel experiments are conducted on a 12.6% maximum thickness, 127 mm chord airfoil. Aerodynamic and structural performance results are presented for a flow rate of 15 m/s and Reynolds Number of 127,000. Non-linear effects due to aerodynamic and piezoceramic hysteresis are identified and discussed. A lift coefficient change of 1.67 is observed purely due to voltage actuation. A maximum L/D ratio of 26.7 is recorded through voltage excitation. Results are compared to conventional, fixed-camber airfoils evaluated by other researchers.

Journal of Solar Energy Engineering, 2001

Micro-electro-mechanical (MEM) translational tabs are introduced for active load control on aerodynamic surfaces such as wind turbine rotor blades. Microtabs are mounted near the trailing edge of rotor blades, deploy approximately normal to the surface, and have a maximum deployment height on the order of the boundary-layer thickness. Deployment of the tab effectively changes the sectional chamber of the rotor blade, thereby changing its aerodynamic characteristics. A tab with tab height to blade section chord ratio, h/c, of 0.01 causes an increase in the section lift coefficient, C1, of approximately 0.3, with minimal drag penalty. This paper presents a proof of concept microtab design and the multi-disciplinary techniques used to fabricate and test the tabs. Computational and experimental wind tunnel results for a representative airfoil using fixed as well as remotely actuated tabs are compared. Although the specifics of load control limitations, including actuation and response t...

Journal of Marine Science and Engineering, 2019

A horizontally submerged passive flapping foil can generate thrust force against the wave propagation using wave energy. This renewable method has been used for the design of propulsion and maneuvering systems of ships and other floating structures. Recently, the passive flapping foils were applied to design the station-keeping system of deep-water floaters. Studies proved that the passively flapping foil system was ineffective in short waves and drift of the floater beyond the design limit was recorded. Therefore, an active flapping foil was investigated as a potential solution to this problem. A computational fluid dynamics (CFD) numerical tool “ANSYS Workbench 19.2” was used to predict the thrust force generated by the active flapping foil in a short wave. Results proved that the active flapping foil can effectively convert wave energy into propulsive energy in short waves and the magnitude of the thrust force depends on the flapping frequency.

This paper describes the results of the experimental verification of the idea of wave-like aquatic propulsion of manned marine vessels first published by one of the present authors (V.V.K.) more than 10 year ago 1 . The idea is based on employing the unique type of localised flexural elastic waves propagating along edges of wedge-like structures immersed in water 1-4 . Such wedge-like structures supporting localised waves can be attached to a body of a small ship or a submarine like fish fins and used for aquatic propulsion (see ). The principle of using localised flexural waves as a source of aquatic propulsion is similar to that used in nature by some fish, e.g. stingrays, that utilise wave-like motions of their large pectoral fins (wings) for moving forward.

Drag reduction for hydrofoils is studied through thrust generation on plunging foils in order to simulate the action of the ocean waves. Force, deformation and flow field measurements are presented for a partially flexible plunging foil in water tunnel experiments. The foil is predominantly rigid with a short flexible trailing-edge plate of length: L = 0.1c, 0.2c, or 0.3c. Appropriate flexibility increases thrust compared to the rigid case. Flexibility is generally more effective for larger lengths of the flexible plate and smaller plunge amplitudes. The maximum observed is therefore for the largest length and smallest amplitude studied: L = 0.3c and a = 0.1c and equates to 28% more thrust than the rigid case. Optima are observed in the non-dimensional rigidity (λ) versus flap angle amplitude (δ) parameter space. These occur at λ ≈ 2 and δ ≈ 7⁰ to 13⁰ for a wide range of flexible plate length and plunge amplitude. Whilst a satisfactory explanation of why there is an optimal flap amplitude remains unavailable, the case of optimal flap angle amplitude results in increased trailingedge vortex circulation, giving a stronger reverse Kármán vortex street and thus a stronger time-averaged jet.

… (AIM), 2011 IEEE/ …, 2011

This paper presents results detailing the performance of a flexible wing for use on a vehicle capable of both aerial and aquatic modes of locomotion, with primary focus on the aquatic substrate. The motivation for the research stems from the ability of avian species ...

Engineering Analysis with Boundary Elements, 2014

Oscillating wings are investigated as unsteady thrusters, augmenting ship 0 s overall propulsion in waves. Flapping propulsor 0 s heave is induced by ship 0 s motions, while pitching motion is set by an active control mechanism. For the detailed investigation of the free-surface effects, a two-dimensional panel method is developed for the hydrodynamic analysis of the flapping hydrofoil. The instantaneous angle of attack is influenced by foil 0 s oscillatory motion and the incident waves. We consider moderate submergence and speed, permitting us to approximately neglect effects of breaking waves and cavitation, and linearize the free-surface boundary conditions and the trailing vortex wake dynamics. Numerical calculations are presented concerning the performance of the developed BEM over a range of motion parameters and compared against other methods and experimental data. Our analysis indicates that significant efficiency is achieved under optimal operating conditions and the free surface effects cannot be neglected. In the presence of waves the thrust coefficient is observed to raise well above its value in infinite domain, with maximum gain reaching 20%, for appropriate selection of the parameters. The present method could serve as a useful tool for the assessment, preliminary design and control of the studied system, extracting energy from sea waves for marine propulsion.

Design and Nature VI, 2012

The high propulsive efficiency, the fast manoeuvrability and the low noise production of the propulsion of marine animals inspired the development of a new ship propeller. This text describes the design of a flapping foil ship propeller and the experiments performed on it. The flapping foil propeller mimics the tail fin of fish that swim at high speed, like tunas or sharks, in at least two ways: the hydrodynamics and the resonant driving mechanism. The motion of the foil is a combination of a heaving and a pitching oscillation, with a phase difference. The wake behind the tail of a fish has a special structure called the reversed von Karman street. If the motion parameters are well chosen, the wake behind the flapping foil has a similar structure, resulting in positive thrust force and high propulsive efficiency. The driving mechanism uses flexibility to exclude the need for one of the two actuators. The influence of the free surface and the oscillation frequency on the performance are investigated.

Decision and Control, …, 2006

The paper investigates the control of tethered airfoils in order to devise a new class of wind generators able to overcome the main limitations of the present aeolian technology based on wind mills. A model taken from the literature is used to simulate the dynamic of a kite which can be controlled by suitably pulling two lines. Energy is generated by a cycle composed of two phases, indicated as the traction and the recovery one. The control unit has two electric drives which act as motors in pulling the lines for controlling the flight or for recovering the kite and as generators if the kite pulls the lines. In each phase, control is obtained by "fast" implementations of suitable NMPC designs. In the traction phase the control is designed such that the kite pulls the lines, maximizing the amount of generated energy. When the maximal length of the lines is reached, the control enters the recovery phase and the kite is driven to a region where the lines can be pulled by the motors until the minimal length is reached, spending a small fraction of the energy generated in the traction phase, and a new traction phase is undertaken. Simulation results are presented, related to a small scale prototype whose construction is undergoing at our laboratory.

2017

The International Moth is a single-handed ultra-lightweight foiling development class boat, and it follows open class rules. Therefore, the designer and builder have full liberty to develop and produce the fastest boat [1]. It is possible to adapt the internal structure of the fixed foil to achieve a tailored twist angle for a given load. Exploring the possibility of using Passive Adaptive Composite (PAC) on the moth hydrofoil to control its pitch angle enables the boat to achieve a stable flight in a wide range of weather conditions whilst reducing the induced drag, passively decreasing the angle of attack in increased boat speed. Using PAC in a multi-element foil, such as the International Moth one, will allow the structure to achieve a constant lift force with speeds higher than the design take-off speed with less need to constantly modifying the rear foil section. Toward the development of a PAC moth fixed foil, experimental and numerical results for a single element aerofoil, a...

The Journal of the Acoustical Society of America, 2008

ABSTRACT: The present paper describes the results of the experimental investigation of a small-scale mono-hull model boat propelled by a localised flexural wave propagating along the plate of finite width forming the boat’s keel. Forward propulsion of the boat was achieved through flexural wave propagation in the opposite direction, which is similar to the aquatic propulsion used in nature by stingrays. The model boat under consideration underwent a series of tests both in a Perspex water tank and in the experimental pool. In particular, the forward velocity of the boat has been measured for different frequencies and amplitudes of the flexural wave. The highest velocity achieved was 32 cm/s. The thrust and propulsive efficiency have been measured as well. The obtained value of the propulsive efficiency in the optimum regime was 51%. This indicates that efficiency of this type of aquatic propulsion is comparable to that of dolphins and sharks (around 75%) and to that of a traditional propeller (around 70%). In contrast to a propeller though, the wave-like aquatic propulsion has the following advantages: It does not generate underwater noise and it is safe for people and marine animals.

Journal of Fluids and Structures, 2005

The performance of an aquatic propulsion system inspired from the thunniform swimming mode is experimentally studied. This consists of generating the propulsive force with a foil undergoing a harmonic flapping which is a combination of a heave translation and a pitch rotation. Experiments are performed at a fixed value of the Reynolds number and of the heave amplitude. The effects of variations of the Strouhal number and of the maximum angle of attack on the thrust force and on the hydromechanical efficiency are investigated. Systematic measurements of the fluid loading show a peak of efficiency of more than 70% for optimal combinations of the parameters. Moreover, a parameter range is identified where efficiency and high thrust conditions are achieved together, as required for use as a propulsion system. When performing experiments on foils undergoing nonsymmetrical flapping, we also observe the maneuvering capacity of such a biomimetic system. r

Sensors and Actuators A: Physical, 1999

We have developed millimeter-scaled magnetic actuators capable of achieving large out-of-plane displacement and large forces using Ž. surface micromachining techniques in conjunction with electroplating of Permalloy Ni Fe. Each actuator consists of a Permalloy 80 20 piece attached to flexural cantilever beams, which are 400 mm long and 100 mm wide. Experiments show that under a 6 = 10 4 Arm external magnetic field, an actuator with the volume of the magnetic piece being 1 mm = 1 mm= 5 mm can reach a 658 angular displacement and exert a 87-mN force in the direction perpendicular to the substrate. We also discuss one potential application of controlling macroscopic fluidic mechanical systems using micromachined actuators. Results on using developed actuators to achieve rolling motion in a macroscaled delta-wing airfoil are presented.

Results in Engineering, 2020

Review of biomimetic flexible flapping foil propulsion systems on different planetary bodies, Results in Engineering,