Dynamic Behaviors of Vortex Ring Rolled Up by a Butterfly Wing and its Dynamic Lift

2016 ◽  
Author(s):  
Masaki Fuchiwaki ◽  
Kazuhiro Tanaka
Keyword(s):  
Flow Field ◽  
Vortex Ring ◽  
Force Measurement ◽  
Three Dimensional ◽  
Vortex Structures ◽  
Dynamic Force ◽  
Butterfly Wing ◽  
Dynamic Behaviors ◽  
Insect Wings ◽  
Piv Measurement

The wing motion of a flying insect such as a butterfly produces fluid force by manipulating the flow field around the wing. These forces enable a butterfly to rapidly accelerate, turn, and hover. A number of recent studies have examined the flow field around insect wings. In recent years, quantitative flow visualization techniques, such as PIV measurement, have been advanced rapidly, and the study of the flow field around insect wings using PIV has been actively performed. As a result, the two- and three-dimensional vortex structures and their dynamic behaviors have been investigated quantitatively. However, the dynamic behaviors of these vortex structures have not been related to the dynamic force characteristics. The purpose of the present study is to clarify the relationship between the dynamic lift generated by the flapping butterfly wing and the dynamic behavior of the vortex ring rolled up from the butterfly wing as well as to investigate the role of the vortex ring. We conducted a dynamic force measurement of a flapping Cynthia cardui using a six-axes sensor and three kinds of shafts: a straight shaft, a short L-shaped shaft, and a long L-shaped shaft. Moreover, a two-dimensional PIV measurement was conducted in the wake of the butterfly. The butterfly is given not only negative dynamic lift but also the reactive force (positive lift) due to the jet flow induced by the vortex ring in the upward flapping. As a result, the butterfly produces dynamic lift in the downward flapping and produces not only negative dynamic lift but also dynamic lift in the upward flapping. Based on these results, it is considered that the vortex ring released into the wake contributes to the dynamic lift generated furing flight. That is, it was concluded that the vortex ring rolled up from the flapping wing has an important role in flight even after being released into the wake.

Characteristics of Dynamic Forces Generated by a Flapping Butterfly and its Wake Structure

2017 ◽  
Author(s):  
Masaki Fuchiwaki ◽  
Kazuhiro Tanaka
Keyword(s):  
Flow Field ◽  
Butterfly Wing ◽  
Vortex Loop ◽  
Insect Wing ◽  
Fluid Forces ◽  
Insect Wings ◽  
Piv Measurement ◽  
Dynamic Forces ◽  
Butterfly Wings ◽  
The Relationship

A typical example of the flow field around a moving elastic body is that around butterfly wings. Butterflies fly by skillfully controlling this flow field, and vortices are generated around their bodies. The motion of their elastic wings produces dynamic fluid forces by manipulating the flow field. For this reason, there has been increased academic interest in the flow field and dynamic fluid forces produced by butterfly wings. A number of recent studies have qualitatively and quantitatively examined the flow field around insect wings. In some such previous studies, the vortex ring or vortex loop formed on the wing was visualized. However, the characteristics of dynamic forces generated by the flapping insect wing are not yet sufficiently understood. The purpose of the present study is to investigate the characteristics of dynamic lift and thrust produced by the flapping butterfly wing and the relationship between the dynamic lift and thrust and the flow field around the butterfly. We conducted the dynamic lift and thrust measurements of a fixed flapping butterfly, Idea leuconoe, using a six-axes sensor. Moreover, two-dimensional PIV measurement was conducted in the wake of the butterfly. The butterfly produced dynamic lift in downward flapping which became maximum at a flapping angle of approximately 0.0 deg. At the same time, the butterfly produced negative dynamic thrust during downward flapping. The negative dynamic thrust was not produced hydrodynamically by a flapping butterfly wing because a jet was not formed in front of the butterfly. The negative dynamic thrust was the kicking force for jumping and the maximum of this kicking force was about 6.0 times as large as the weight. On the other hand, the butterfly produced dynamic thrust in upward flapping which was approximately 6.0 times as large as the weight of the butterfly. However, the attacking force by the abdomen of the butterfly was included in the dynamic thrust and we have not yet clarified quantitatively the dynamic thrust produced by the butterfly wing.

Three-Dimensional Vortex Structure Around a Free Flight Butterfly

2014 ◽  
Author(s):  
Masaki Fuchiwaki ◽  
Taichi Kuroki ◽  
Kazuhiro Tanaka ◽  
Takahide Tabata
Keyword(s):  
Flow Field ◽  
Dynamic Behavior ◽  
Vortex Ring ◽  
Vortex Structure ◽  
Three Dimensional ◽  
Vertical Direction ◽  
Micro Air Vehicles ◽  
Free Flight ◽  
Single Vortex ◽  
Piv Measurement

Micro-air-vehicles (MAVs) and micro-flight robots that mimic the flight mechanisms of insects have attracted significant attention. From this reason, the flight mechanism of the butterflies and their flow fields also has attracted attention. A number of studies on the mechanism of butterfly flight have been carried out. Moreover, a number of recent studies have examined the flow field around insect wings. The present authors conducted a particle image velocimetry (PIV) measurement around the flapping wings of Cynthia cardui and Idea leuconoe and investigated the vortex structure and dynamic behavior produced. However, these results are for a flow field under a fixed condition. The vortex flow structure and the dynamic behavior generated by the wings of a butterfly in free flight are expected to be important for generating the aerodynamic forces required for flight. In the present study, we attempt to clarify the three-dimensional vortex structure around a butterfly in free flight by a scanning PIV measurement. The vortex ring formed by the front wings during the flapping downward grows without attenuation toward the wake. Moreover, during the flapping upward of the wings, a vortex rolls up from the wing, eventually forming a single vortex ring. This vortex ring forms in the vertical direction in contrast to vortex ring formed during the flapping downward, and we may anticipate that the two vortex rings interfere with each other as they advance toward the wake.

scholarly journals Numerical and Experimental Analyses of Three- Dimensional Unsteady Flow around a Micro-Pillar Subjected to Rotational Vibration

Micromachines ◽  
2018 ◽  
Vol 9 (12) ◽  
pp. 668 ◽  
Author(s):  
Kanji Kaneko ◽  
Takayuki Osawa ◽  
Yukinori Kametani ◽  
Takeshi Hayakawa ◽  
Yosuke Hasegawa ◽  
...  
Keyword(s):  
Flow Field ◽  
Moving Boundary ◽  
Three Dimensional ◽  
Steady Streaming ◽  
Micro Piv ◽  
Piv Measurement ◽  
Image Velocimetry ◽  
Measurement Tools ◽  
Rotational Vibration ◽  
Induced Flow

The steady streaming (SS) phenomenon is gaining increased attention in the microfluidics community, because it can generate net mass flow from zero-mean vibration. We developed numerical simulation and experimental measurement tools to analyze this vibration-induced flow, which has been challenging due to its unsteady nature. The validity of these analysis methods is confirmed by comparing the three-dimensional (3D) flow field and the resulting particle trajectories induced around a cylindrical micro-pillar under circular vibration. In the numerical modeling, we directly solved the flow in the Lagrangian frame so that the substrate with a micro-pillar becomes stationary, and the results were converted to a stationary Eulerian frame to compare with the experimental results. The present approach enables us to avoid the introduction of a moving boundary or infinitesimal perturbation approximation. The flow field obtained by the micron-resolution particle image velocimetry (micro-PIV) measurement supported the three-dimensionality observed in the numerical results, which could be important for controlling the mass transport and manipulating particulate objects in microfluidic systems.

Feasibility Study on Application of a Self-Formed Flow Field Downstream of Elbows to Divertor Cooling

2013 ◽  
Author(s):  
Shoichi Kodate ◽  
Tatsuya Kubo ◽  
Shinji Ebara ◽  
Hidetoshi Hashizume
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Reynolds Stress ◽  
Swirling Flow ◽  
Pipe Wall ◽  
Three Dimensional ◽  
High Heat ◽  
Turbulent Pipe Flow ◽  
High Heat Transfer ◽  
Piv Measurement

In this study, the characteristic of the swirling flow was analyzed in detail in terms of flow field by means of a visualization experiment using matched refractive index PIV measurement to evaluate the applicability of the swirling flow generated downstream of a three-dimensionally connected dual elbow to the divertor cooling. The dual elbow used in the experiment comprises two 90-degree elbows with the same curvature connected directly in three-dimensional configuration. From the experiment, it was found that strong swirling velocity component appears locally near the pipe wall downstream of the second elbow. Moreover, although the strength of the swirling flow changed gradually as it flowed downstream, it attenuated little even 8D downstream of the dual elbow, where D was the diameter of the piping. Therefore, this swirling flow is expected to survive for a considerable distance downstream of the elbow, and the applicability of this flow field to divertor cooling can be promising. Furthermore turbulence quantities such as Reynolds stress were analyzed in terms of heat transfer performance. Since there were some regions where larger Reynolds stress than a developed turbulent pipe flow was observed near the pipe wall, high heat transfer is expected there.

scholarly journals Aerodynamics of Flapping Wing at Low Reynolds Numbers: Force Measurement and Flow Visualization

2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
Abhijit Banerjee ◽  
Saurav K. Ghosh ◽  
Debopam Das
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Flow Visualization ◽  
Force Measurement ◽  
Reynolds Numbers ◽  
Flapping Flight ◽  
Water Tank ◽  
Cross Sectional ◽  
Piv Measurement ◽  
The Difference

Flow field of a butterfly mimicking flapping model with plan form of various shapes and butterfly-shaped wings is studied. The nature of the unsteady flow and embedded vortical structures are obtained at chord cross-sectional plane of the scaled wings to understand the dynamics of insect flapping flight. Flow visualization and PIV experiments are carried out for the better understanding of the flow field. The model being studied has a single degree of freedom of flapping. The wing flexibility adds another degree to a certain extent introducing feathering effect in the kinematics. The mechanisms that produce high lift and considerable thrust during the flapping motion are identified. The effect of the Reynolds number on the flapping flight is studied by varying the wing size and the flapping frequency. Force measurements are carried out to study the variations of lift forces in the Reynolds number (Re) range of 3000 to 7000. Force experiments are conducted both at zero and finite forward velocity in a wind tunnel. Flow visualization as well as PIV measurement is conducted only at zero forward velocity in a stagnant water tank and in air, respectively. The aim here is to measure the aerodynamic lift force and visualize the flow field and notice the difference with different Reynolds number (Re), and flapping frequency (f), and advance ratios (J=U∞/2ϕfR).

Characteristics of Dynamic Forces Generated by a Flapping Butterfly

2013 ◽  
Author(s):  
Taichi Kuroki ◽  
Masaki Fuchiwaki ◽  
Kazuhiro Tanaka ◽  
Takahide Tabata
Keyword(s):  
Flow Field ◽  
Vortex Ring ◽  
Elastic Deformation ◽  
Micro Air Vehicles ◽  
Flapping Wing ◽  
Flapping Motion ◽  
Insect Wings ◽  
Dynamic Forces ◽  
The Relationship ◽  
Significant Attention

Many studies on the mechanism of butterfly flight have been carried out. A number of recent studies have examined the flow field around insect wings. Moreover, Micro-air-vehicles and micro-flight robots that mimic the flight mechanisms of insects have attracted significant attention, and a number of MAVs and micro-flight robots that use various devices have been reported. However, these robots were not practical. One of the reasons for this is that the flying mechanism of insects has not yet been clarified sufficiently. The present authors developed a flapping-wing robot without tail wings and focused on the flow field around the wings created by the flapping motion and its elastic deformation. In the present study, we attempt to clarify the relationship between the vortex ring over the wing and the dynamic lift generated by the flapping wing. The dynamic lift becomes large rapidly in the downward flapping and reaches a maximum at a flapping angle of −30 deg. After the maximum, the dynamic lift decreases gradually and the dynamic lift in upward flapping is approximately constant. The growth of the vortex ring formed by the flapping wing was clarified to contribute significantly to the dynamic lift acting on the butterfly. We should consider the interaction of both vortex ring both in downward flapping and in upward flapping in order to estimate the dynamic lift exactly using the circulation of the vortex ring.

scholarly journals Reynolds stress tensor and pressure-related turbulence transport terms measured by time-resolved tomographic-PIV

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Jose Roberto Moreto ◽  
Xiaofeng Liu
Keyword(s):  
Flow Field ◽  
Turbulent Flow ◽  
Turbulent Flows ◽  
High Speed ◽  
Three Dimensional ◽  
Time Resolved ◽  
Tomographic Piv ◽  
Piv Measurement ◽  
Derivatives Of

Turbulence is inherently a three-dimensional and time dependent flow phenomenon (Pope, 2001). Because of the ubiquitous existence of turbulent flows in nature, accurate characterization of turbulent flows, either through experimental measurements or through direct numerical simulations, is of paramount importance for modeling turbulence (Liu and Katz, 2018). Since its inception in 1984 (Adrian, 1984), Particle Image Velocimetry (PIV), among several other conventional techniques used for turbulence measurements, has been a valuable tool for providing reliable experimental data for turbulence research. Several advancements in hardware such as high-speed cameras, together with innovative algorithms and procedures, have extended the scope of PIV to a variety of applications. Westerweel et al. (2013) point out in a recent review article that one of the main advantages of the PIV measurement is its unique ability in measuring quantitatively spatial derivatives of the flow field. With the development of Tomographic PIV introduced by Elsinga et al. (2006), it is now possible to measure simultaneously the distributions of three velocity components in a three-dimensional flow field, thus enabling us to measure all the velocity derivatives of a turbulent flow. However, for a thorough characterization of a turbulent flow, in addition to the velocity gradients, the instantaneous pressure distribution in the 3D flow field also needs to be measured.

scholarly journals Numerical and Experimental Analyses of Three-Dimensional Unsteady Flow Around a Micro-Pillar Subjected to Rotational Vibration

2018 ◽  
Author(s):  
Kanji Kaneko ◽  
Takayuki Osawa ◽  
Yukinori Kametani ◽  
Takeshi Hayakawa ◽  
Yosuke Hasegawa ◽  
...  
Keyword(s):  
Flow Field ◽  
Moving Boundary ◽  
Three Dimensional ◽  
Steady Streaming ◽  
Micro Particle Image Velocimetry ◽  
Piv Measurement ◽  
Image Velocimetry ◽  
Measurement Tools ◽  
Rotational Vibration ◽  
Induced Flow

The steady streaming (SS) phenomenon is gaining increased attention in the microfluidics community, because it can generate net mass flow from the zero-mean vibration. We developed numerical simulation and experimental measurement tools to analyze this vibration induced flow, which has been challenging due to its unsteady nature. Validity of these analysis methods is confirmed by comparing the three-dimensional (3D) flow field induced around a cylindrical micropillar under circular vibration. In the numerical modeling, we directly solved the flow in the Lagrangian frame so that the substrate with a micropillar becomes stationary, and the result was converted to the Eulerian frame to compare them with the experimental results. The present approach enables to avoid the introduction of moving boundary or small perturbation approximation. The flow field obtained by the micro particle image velocimetry (PIV) measurement supported the three-dimensionality observed in the numerical results, which could be important for controlling the mass transport and manipulating particulate objects in the microfluidic systems.

Vortex Structure of a Vortex Ring Over a Butterfly Wing and its Dynamic Behavior

2011 ◽  
Author(s):  
Masaki Fuchiwaki ◽  
Taichi Kuroki ◽  
Kazuhiro Tanaka ◽  
Takahide Tabata
Keyword(s):  
Dynamic Behavior ◽  
Vortex Ring ◽  
Large Scale ◽  
Leading Edge ◽  
Micro Air Vehicles ◽  
Butterfly Wing ◽  
Trailing Edge ◽  
Piv Measurement ◽  
Large Scale Vortex ◽  
Secondary Disasters

Micro-Air-Vehicles (MAVs) that mimic the flight mechanisms of insects have been attracting significant attention in recent years. These technologies are developed with the aim of lifesavings in the area with the risk of secondary disasters, maintenance works for constructions such as bridges, information collection on planet searches, monitoring of security risks for the purpose of security means. A number of researchers have attempted to develop small flap flying objects and MAV with various actuators and devices. However, these robots were not practical. One of the reasons for this is that the flying mechanism of insects has not yet been clarified sufficiently. We have clarified that a couple of large-scale vortex is formed over the wing. The purpose of the present study is to clarify the dynamic behavior and the detailed structure of the vortices of the flapping butterfly wing, and we carried out the PIV measurement around the flapping butterfly wing. The vortex ring develops over the wings when the wings flap downward to the bottom dead position and then passes through the butterfly completely and grows until reaching the wake at the bottom dead position. The vortex ring develops over the wing while growing from the leading edge toward the trailing edge. The maximum vorticity of the vortex ring over the wing moves from the leading edge to the trailing edge with the downward flapping. On the other hand, the vorticity of the LEV decays with downward flapping.

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