Bulletin of the American Physical Society
71st Annual Meeting of the APS Division of Fluid Dynamics
Volume 63, Number 13
Sunday–Tuesday, November 18–20, 2018; Atlanta, Georgia
Session G14: Aerodynamics: Fluid Structure Interaction II |
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Chair: David MacPhee, The University of Alabama Room: Georgia World Congress Center B301 |
Monday, November 19, 2018 10:35AM - 10:48AM |
G14.00001: Fluid-Structure Instabilities in Flow Energy Harvesting Applications Benedikt Dorschner, Luis Phillipe Tosi, Tim Colonius Building fully autonomous and self-sustained electronic devices requires reliable in-situ power generation methods. A robust and promising approach is energy harvesting using fluid kinetic energy as its source. Among various proposed transduction mechanisms, we will focus on vibration-based piezoelectricity due to its robustness, high power density and electro-mechanical coupling efficacy. When coupled to fluid flow, exploiting fluid-structure instabilities to maintain self-sustained oscillations for consistent power output has shown to be an effective harvesting strategy. In this contribution, we will investigate the stability properties of an energy harvester design based on a piezoelectric beam, which is placed in a converging-diverging channel configuration. Using fully coupled three-dimensional direct numerical simulations of the fluid-structure interaction problem, we will deduce and validate a quasi one-dimensional model of the system based on leakage-flow type instability. This eventually allows us to identify the main mechanisms of fluid-induced vibration, which will be paramount for designing next-generation energy harvesters.
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Monday, November 19, 2018 10:48AM - 11:01AM |
G14.00002: Could implantable body flow sensors be self-powered? Lucy Elaine Fitzgerald, Maria Lilibeth Contreres, Daniel Quinn The rise of Smart Health has led to implantable healthcare devices that can diagnose and monitor diseases in real-time. Some diagnoses are based on fluids in the body: reduced lung flow may indicate an asthma attack, and high turbulence in the blood may indicate hemolysis. A key challenge of current `implantables’ is that they are difficult to power and require iterative surgeries to replace batteries. Here we show that a piezoelectric flow sensor could monitor a fluid flow and power itself from the same flow at the same time. The effectiveness of this dual-purpose sensor/harvester depends on flow properties. A sensor that measures flowrate needs a different duty cycle than one that measures subtle abnormalities, such as turbulent wakes caused by inflammation. In the human airway, a sensor could use bidirectional airflow to create an oscillating voltage directly. In unidirectional artery flow, sensing/harvesting depends on complex fluid-structure interactions like flutter. This variation allows a breadth of applications, but it also demands advanced models that capture the tradeoffs between sensing fidelity and harvesting potential. To develop these models, we built a platform for testing the sensing/harvesting capability of piezocantilevers in bio-inspired oscillating flows. |
Monday, November 19, 2018 11:01AM - 11:14AM |
G14.00003: A First Look at Side-by-Side Piezoelectric Harvesters in Fractal Square Grid-Generated Turbulence Kevin Ferko, David Lachendro, Nicholas Chiappazzi, Amir Danesh-Yazdi While the vast majority of the literature in energy harvesting is dedicated to resonant harvesters, non-resonant harvesters, especially those that use turbulence-induced vibration to generate energy, have not been studied in as much detail. This is especially true for grid-generated turbulence. In this study, the interaction of two side-by-side fluidic harvesters from a passive fractal square grid-generated turbulent flow is considered. The fractal grid has been shown to significantly increase the turbulence generated in the flow which is the source of the vibration of the piezoelectric beams. In this experimental study, the influence of four parameters have been investigated: (i) Beam lengths and configurations, (ii) Mean flow velocity, (iii) Distance from the grid and (iv) Gap between two beams. Experimental results show that the power output per beam from the fractal square grid is at worst similar to the output from a classical grid with a much larger blockage ratio. |
Monday, November 19, 2018 11:14AM - 11:27AM |
G14.00004: A Galloping Energy Harvester with Attached Flow Near The Zero Displacement Position Sam Tucker Harvey, Petr Denissenko, Igor A Khovanov Interest in aeroelastic energy harvesters has grown substantially in recent years due to the potential for low maintenance and low cost energy solutions, particularly with regard to wireless sensors and microelectromechanical systems. The development of aeroelastic energy harvesters to date has focused mainly on the flutter of airfoils, the galloping of prismatic structures and vortex induced vibrations as a means to generate energy. |
Monday, November 19, 2018 11:27AM - 11:40AM |
G14.00005: Energy extraction from water waves using a moving piezoelectric plate Kourosh Shoele Different techniques have been proposed to convert the sea energy ( wave and current) to useful thrust or useful electrical energy. Here, the application of a moving piezoelectric flexible plate for energy extraction from sea waves is discussed. The hydrodynamics of a piezoelectric flexible submerged plate close to a free surface that is exposed to uniform flow velocity and either a head or following incoming harmonic surface wave is studied analytically. Using a continuous vortex sheet of oscillating strength and proper image system to represent the effect of the plate and the free surface on the flow field, we solve for the fluid-structure-electric interaction. The energy harvesting efficiency of the piezoelectric plate is investigated, and it is shown how the resistance and inductance characteristics of the plate along with the Froude number and the bending flexibility of the plate affect the energy extraction efficiency of the system and the optimal parameters are identified. The oscillating mode shape for most efficient cases are examined, and the importance of the moving velocity on the system energy conversion will be compared over a range of parameters. |
Monday, November 19, 2018 11:40AM - 11:53AM |
G14.00006: Energy harvesting and vortex wake structure of an oscillating hydrofoil at high Reynolds number Bernardo Luiz Rocha Ribeiro, Jennifer A Franck The energy extraction potential from the sinusoidal heaving and pitching motion of an elliptical hydrofoil is explored through direct numerical simulations (DNS) at a Reynolds number of 1,000 and large eddy simulations (LES) at a Reynolds number of 50,000. The LES is able to capture the time-dependent vortex shedding and dynamic stall properties of the foil as it undergoes high relative angles of attack. At a reduced frequency of fc/U∞ = 0.1 the high Reynolds number flow has a 1.4-3.6% increase in power compared to the low Reynolds, however at fc/U∞ = 0.15 the enhancement in power is as much as 6.7%. It is found that a stronger leading edge vortex and faster vortex convection times can enhance the vertical force coefficient to yield more power throughout a portion of the stroke in comparison with the low Reynolds simulations. The organized vortical structures of the wake in terms of vortex location and strength are analyzed for future multiple-foil array configurations via a vortex tracking algorithm. |
Monday, November 19, 2018 11:53AM - 12:06PM |
G14.00007: Experimental Investigation of Impulsive Motions of Flapping Foils to Produce Large, Transient Lift and Thrust Forces Miranda Kotidis, Michael Triantafyllou As underwater vehicles become increasingly versatile and capable, bio-inspired propulsion systems are becoming a viable possibility for future vehicles. In particular, flapping foil actuators are promising in their abilities for propulsion and maneuvering. Current underwater vehicles rely on propellers, which form a jet wake to produce propulsion forces, and as such, experience an inherent delay between the movement of the propeller and the vehicle feeling a propulsive force. To mitigate this shortcoming, flapping foils were tested to produce large, transient forces in still water. These swift, one-time strokes take advantage of added mass/inertial effects and large, stably attached vortices to produce propulsive forces almost instantaneously. Various trajectories in heave and pitch were tested and analyzed to compare to previous work. Further work includes optimizing the trajectory to produce the desired propulsion forces for vehicle control and maneuvering. |
Monday, November 19, 2018 12:06PM - 12:19PM |
G14.00008: Linearized potential theory of flapping foils in tandem configuration Javier Alaminos-Quesada, Ramon Fernandez-Feria A vortical impulse theory is used to compute the lift, thrust and moment of two-dimensional flapping foils in tandem configuration within the framework of unsteady linear potential theory. First, general expressions are derived for any set of oscillating foils of arbitrary chord lengths, taking into account the effect of their unsteady wakes and the interaction of any set of moving point vortices. Then, analytical explicit solutions for the lift, thrust and moment are obtained for the specific case of two oscillating airfoils in tandem configuration. In the limit of large separation distance, we recover the expressions of a single oscillating foil for the forewing, but the hindwing is always affected by the unsteady wake of the forewing. These potential results are compared with available experimental and numerical data, with good agreement for small amplitude of the oscillations and sufficiently high Reynolds numbers. |
Monday, November 19, 2018 12:19PM - 12:32PM |
G14.00009: Abstract Withdrawn
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Monday, November 19, 2018 12:32PM - 12:45PM |
G14.00010: Stability Analyses of a Foil with an Active Trailing-edge Flap Tso-Kang Wang, Kourosh Shoele The aeroelastic fluttering response is a standard feature of airfoils in many different applications such as aero-vehicles, renewable energy extraction, and animal locomotion. Often, to enhance the performance and increase the reliability of a particular system, the fluttering response should be suppressed or controlled. In this work, we investigated how the active flap can be utilized to modify the flow around the airfoil and thus regulate the aeroelastic response. Through a high-fidelity fluid-structure interaction algorithm, the active flap is shown to be an effective regulating mechanism for the fluttering response. The importance of deflecting angle and frequency of the flap on the fluttering control is discussed, and the connection between dominant flow features and dynamic responses of the foil is drawn. Furthermore, a novel stability analysis is proposed to form a reduced-order representation of the problem and its proficiency in capturing different physical phenomena of the system is demonstrated. |
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