Experimental study of flapping foil propulsion system for ships and underwater vehicles and PIV study of caudal fin propulsors
01 Oct 2014-pp 1-7
TL;DR: In this article, an electro-mechanical drive and transmission system is designed to actuate a pair of oscillating foils fitted at the bottom of a ship model. And the authors experimentally study the application of a lift-based fore flipper locomotion applied to a 3m ship model, the concept of which resembles to the propulsion of penguins and turtles.
Abstract: Deep sea aquatic animal propulsors are classified into four main categories lift-based propulsion, drag-based propulsion, undualtion mode and jet propulsion. In order to develop combined flapping and undulation mode propulsion for ships and underwater vehicles a brief introduction is given to lift-based propulsors and undulation mode. Combined bio-mimetic flapping and undulation mode propulsion systems for underwater vehicles have advantages such as ecologically pure, relatively low operational frequency and higher efficiency. This system can combine the function of propulsor, control device and stabilizer, provides static thrust, high maneuverability, less conspicuous wake and less cavitation problem than conventional propellers. In this paper, we experimentally study the application of a lift-based fore flipper locomotion applied to a 3m ship model, the concept of which resembles to the propulsion of penguins and turtles and present the results and observations. An electro-mechanical drive and transmission system is designed to actuate a pair of oscillating foils fitted at the bottom of the ship model. The model performances, both resistance and propulsion aspects, were studied. Sharks exhibit high-performance aquatic locomotion through oscillation of its homocercal forked caudal fin. This paper also presents the PIV measurements carried out on a live shark fish to understand and analyze the hydrodynamic behavior of its propulsion using the caudal fin. The velocity vector plots shows that the fins and caudal fins produce reverse von Karman vortex street resulting in a aftward jet formation which gives it the propulsive force.
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TL;DR: The hydrodynamics of the swimming modes occurring in fish are recalled and the more relevant lines of investigation of computational models are summarized to provide an efficient, cheap, and fast alternative tool to analyze biomimetic marine propulsors.
Abstract: The aim of the present paper is to provide the state of the works in the field of hydrodynamics and computational simulations to analyze biomimetic marine propulsors Over the last years, many researchers postulated that some fish movements are more efficient and maneuverable than traditional rotary propellers, and the most relevant marine propulsors which mimic fishes are shown in the present work Taking into account the complexity and cost of some experimental setups, numerical models offer an efficient, cheap, and fast alternative tool to analyze biomimetic marine propulsors Besides, numerical models provide information that cannot be obtained using experimental techniques Since the literature about trends in computational simulations is still scarce, this paper also recalls the hydrodynamics of the swimming modes occurring in fish and summarizes the more relevant lines of investigation of computational models
20 citations
TL;DR: In this paper, the effect of self-agitator motion on the dynamic vortex shedding is characterized by employing time-resolved particle image velocimetry (TR-PIV) at the midspan of the agitator within a Reynolds number range of about 1300-6800 in a customized single channel.
10 citations
TL;DR: In this article, the effect of nonsinusoidal trajectory on the propulsive performances and the vortex shedding process behind a flapping airfoil is investigated, where an elliptic function with an adjustable parameter S (flattening parameter) is used to realize various nonsinsooidal trajectories of both motions.
Abstract: The effect of nonsinusoidal trajectory on the propulsive performances and the vortex shedding process behind a flapping airfoil is investigated in this study. A movement of a rigid NACA0012 airfoil undergoing a combined heaving and pitching motions at low Reynolds number (Re¼11,000) is considered. An elliptic function with an adjustable parameter S (flattening parameter) is used to realize various nonsinusoidal trajectories of both motions. The two-dimensional (2D) unsteady and incompressible Navier–Stokes equation governing the flow over the flapping airfoil are resolved using the commercial software STAR CCMþ. It is shown that the nonsinusoidal flapping motion has a major effect on the propulsive performances of the flapping airfoil. Although the maximum propulsive efficiency is always achievable with sinusoidal trajectories, nonsinusoidal trajectories are found to considerably improve performance: a 110% increase of the thrust force was obtained in the best studied case. This improvement is mainly related to the modification of the heaving motion, more specifically the increase of the heaving speed at maximum pitching angle of the foil. The analysis of the flow vorticity and wake structure also enables to explain the drop of the propulsive efficiency for nonsinusoidal trajectories.
9 citations
Dissertation•
24 Jun 2018
TL;DR: In this article, a hybrid numerical model was developed to capture the free running response of a flapping foil wave powered vessel, and this model has been validated by the experimental analysis.
Abstract: Wave propelled vessels utilize submerged flapping foils to convert wave energy directly into propulsion. This works by coupling the response of foils operating in a wavy flow with the flapping motion driven by the wave-induced hull motions. For platforms that are solely propelled using this method the free running forward speed is dictated by the magnitude and frequency of the ambient wave energy. Submerged flapping foils also have the potential to recover wave energy for onboard power generation, and, in this way, a vessel could be both powered and propelled by the ambient wave energy. This thesis both numerically and experimentally investigates the coupled dynamic response of a wave powered vessel, which enables the prediction of the free running forward speed and an assessment of the potential for wave energy recovery. A hybrid numerical model has been developed to capture the free running response of a flapping foil wave powered vessel, and this model has been validated by the experimental analysis. The hybrid method combines the frequency domain strip theory approach for solving the seakeeping response with a time domain solution for the response of a spring loaded flapping foil. The numerical model also evaluates the electromechanical conversion of wave energy by modelling the power generated by a permanent magnet tubular linear generator. Free running wave propulsion experiments were performed in both regular head and following waves using a model with spring loaded flapping foils at the bow and stern over a range of wave frequencies. The experimental setup incorporated wave energy recovery in the form of electrical power by linking the flapping foils with a power take-off device, and a series of experiments were conducted for different wave heights and frequencies. In addition to validating the numerical model, the experimental results show a notable difference in the response of the forward and aft foils in head and following waves, and confirm numerical predictions that the optimal location of the foils is at or beyond the perpendiculars of the vessel. Furthermore, the experimental and numerical analysis demonstrate that it is possible to recover wave energy from the use of submerged foils. Numerical simulations have been carried out to provide a more detailed insight into the effect on the coupled response of: foil size and location; flapping parameters; and seakeeping characteristics. In particular, it is shown that the wave-phasing parameter and the foil spring constant is of significant importance for the efficiency of wave propulsion. Lastly, the numerical analysis provides guidance for the design of flapping foil wave powered vessels, and highlights the importance of the wavelength to vessel length ratio.
7 citations
Cites background or result from "Experimental study of flapping foil..."
...However, at higher Strouhal numbers the efficiencies tend towards 55%, in agreement with the results of Babu et al. (2014). At lower Strouhal numbers, the efficiency decreases dramatically, which shows the importance of the Strouhal number on the propulsive performance. Thaweewat et al. (2018) have recently published a numerical study that investigated the difference between prescribed foil pitch and a spring loaded flapping foil for maritime propulsion....
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...However, model ship experiments with a pair of flexible flapping foils only achieved a comparatively low propulsive efficiency of approximately 55% (Babu et al. (2014))....
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...However, at higher Strouhal numbers the efficiencies tend towards 55%, in agreement with the results of Babu et al. (2014). At lower Strouhal numbers, the efficiency decreases dramatically, which shows the importance of the Strouhal number on the propulsive performance....
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TL;DR: In this article , the authors proposed a systematic enhancement scheme of the static and dynamic performances of the biomimetic fin in a low-speed regime, which involves rigid, cupping, and flexible single-joint fin of the acceleration-reaction fin mechanism and a high aspect ratio lunate shape two-jinkel-based fin mechanism.
3 citations
References
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TL;DR: In this article, the principal mechanism for producing propulsive and transient forces in oscillating flexible bodies and fins in water, the formation and control of large-scale vortices, was identified.
Abstract: Interest in novel forms of marine propulsion and maneuvering has sparked a number of studies on unsteadily operating propulsors. We review recent experimental and theoretical work identifying the principal mechanism for producing propulsive and transient forces in oscillating flexible bodies and fins in water, the formation and control of large-scale vortices. Connection with studies on live fish is made, explaining the observed outstanding fish agility.
816 citations
TL;DR: In this article, a review of the basic mechanisms of force production and flow manipulation in oscillating foils for underwater use is presented, focusing primarily on experimental studies on some of the, at least partially understood, mechanisms, which include the formation of streets of vortices around and behind two-and three-dimensional propulsive oscillating flapping foils.
Abstract: Significant progress has been made in understanding some of the basic mechanisms of force production and flow manipulation in oscillating foils for underwater use. Biomimetic observations, however, show that there is a lot more to be learned, since many of the functions and details of fish fins remain unexplored. This review focuses primarily on experimental studies on some of the, at least partially understood, mechanisms, which include 1) the formation of streets of vortices around and behind two- and three-dimensional propulsive oscillating foils; 2) the formation of vortical structures around and behind two- and three-dimensional foils used for maneuvering, hovering, or fast-starting; 3) the formation of leading-edge vortices in flapping foils, under steady flapping or transient conditions; 4) the interaction of foils with oncoming, externally generated vorticity; multiple foils, or foils operating near a body or wall.
442 citations
"Experimental study of flapping foil..." refers background in this paper
...Flexible flaps are chosen because they are found to be more efficient than rigid ones[1,2]....
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...Recent research and development on flapping foils and wings, both experimental and theoretical analysis, have shown that such systems at optimum conditions could achieve high thrust levels, Triantafyllou et al [1],[2], Taylor et al [3], Ellenrieder et al [4]....
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TL;DR: It is shown that the transition from a B vK wake to a reverse BvK wake precedes the actual drag-thrust transition and the significance of the present results in the analysis of flapping systems in nature is discussed.
Abstract: We study experimentally the vortex streets produced by a flapping foil in a hydrodynamic tunnel, using two-dimensional particle image velocimetry. An analysis in terms of a flapping frequency-amplitude phase space allows the identification of (i) the transition from the well-known Benard-von Karman (BvK) wake to the reverse BvK vortex street that characterizes propulsive wakes, and (ii) the symmetry breaking of this reverse BvK pattern giving rise to an asymmetric wake. We also show that the transition from a BvK wake to a reverse BvK wake precedes the actual drag-thrust transition and we discuss the significance of the present results in the analysis of flapping systems in nature.
220 citations
"Experimental study of flapping foil..." refers background in this paper
...5 ) these vortices rotate outward to the mean position of the foil, and it is termed as reverse von Karman vortices[15]....
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TL;DR: The physical and the design factors are discussed, which affect the aerohydrodynamic characteristics of flapping wings and that therefore have to be accounted for in the modern mathematical models.
217 citations
"Experimental study of flapping foil..." refers background in this paper
...Rozhdestvensky & Ryzhov[5], and Naito & Isshiki[6] present the study of flapping-bow wings on ship propulsion....
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TL;DR: Two alternative particle image velocimetry (PIV) methods have been developed, applying laser light sheet illumination of particle-seeded flows around marine organisms to map the flow velocity in two-dimensional planes, offering detailed quantitative descriptions of the flow morphology.
Abstract: Two alternative particle image velocimetry (PIV) methods have been developed, applying laser light sheet illumination of particle-seeded flows around marine organisms. Successive video images, recorded perpendicular to a light sheet parallel to the main stream, were digitized and processed to map the flow velocity in two-dimensional planes. In particle tracking velocimetry (PTV), displacements of single particles in two subsequent images were determined semi-automatically, resulting in flow diagrams consisting of non-uniformly distributed velocity vectors. Application of grid-cell averaging resulted in flow field diagrams with uniform vector distribution. In sub-image correlation PIV (SCPIV), repetitive convolution filtering of small sub-areas of two subsequent images resulted in automatic determination of cross-correlation peaks, yielding flow field diagrams with regularly spaced velocity vectors. In both PTV and SCPIV, missing values, caused by incomplete particle displacement information in some areas of the images or due to rejection of some erroneous vectors by the vector validation procedure, were interpolated using a two-dimensional spline interpolation technique. The resultant vector flow fields were used to study the spatial distribution of velocity, spatial acceleration, vorticity, strain and shear. These flow fields could also be used to test for flow in the third dimension by studying the divergence, and to detect the presence and location of vortices. The results offer detailed quantitative descriptions of the flow morphology and can be used to assess dissipated energy. The versatile character of the technique makes it applicable to a wide range of fluid mechanical subjects within biological research. So far it has been successfully applied to map the flow around swimming copepods, fish larvae and juvenile fish and the ventilation current of a tube-living shrimp.
140 citations