Effect of wing mass on the free flight of a butterfly-like model using immersed boundary–lattice Boltzmann simulations

2019 ◽  
Vol 877 ◽  
pp. 614-647 ◽  
Author(s):  
K. Suzuki ◽  
I. Okada ◽  
M. Yoshino
Keyword(s):  
Lattice Boltzmann ◽  
Total Mass ◽  
Aerodynamic Force ◽  
Inertial Force ◽  
Leading Edge ◽  
The Body ◽  
Immersed Boundary ◽  
Mass Ratio ◽  
Free Flight ◽  
Lattice Boltzmann Simulations

The wings of butterflies are relatively heavier than those of other insects, and the inertial force and torque due to the wing mass are likely to have a significant effect on agility and manoeuvrability in the flapping flight of butterflies. In the present study, the effect of wing mass on the free flight of butterflies is investigated by numerical simulations based on an immersed boundary–lattice Boltzmann method. We use a butterfly-like model consisting of two square wings with mass connected by a rod-shaped body. We simulate the free flights of the model by changing the ratio of the wing mass to the total mass of the model and also changing the mass distributions of the wings. As a result, we find that the aerodynamic vertical and horizontal forces decrease as the wing-mass ratio increases, since for a large wing-mass ratio the body has large vertical and horizontal oscillations in each stroke and consequently the speeds of the wing tip and the leading edge relatively decrease. In addition, we find that the wing-mass ratio has a dominant effect on the rotational motion of the model, and a large wing-mass ratio reduces aerodynamic force and intensifies the time variation of the pitching angle. From the results of our free flight simulations, we clarify the critical wing-mass ratio between upward flight and downward flight and find that the critical wing-mass ratio is a function of the non-dimensional total mass and almost independent of the wing length. Then, we evaluate the effect of the wing-mass distribution on the critical wing-mass ratio. Finally, we discuss the limitations of the model.

scholarly journals Flying in reverse: kinematics and aerodynamics of a dragonfly in backward free flight

2018 ◽  
Vol 15 (143) ◽  
pp. 20180102 ◽  
Author(s):  
Ayodeji T. Bode-Oke ◽  
Samane Zeyghami ◽  
Haibo Dong
Keyword(s):  
High Speed ◽  
Aerodynamic Force ◽  
Force Production ◽  
Leading Edge ◽  
The Body ◽  
Body Posture ◽  
Immersed Boundary ◽  
Reconstruction Method ◽  
Free Flight ◽  
The Us

In this study, we investigated the backward free flight of a dragonfly, accelerating in a flight path inclined to the horizontal. The wing and body kinematics were reconstructed from the output of three high-speed cameras using a template-based subdivision surface reconstruction method, and numerical simulations using an immersed boundary flow solver were conducted to compute the forces and visualize the flow features. During backward flight, the dragonfly maintained an upright body posture of approximately 90° relative to the horizon. The upright body posture was used to reorient the stroke plane and the flight force in the global frame; a mechanism known as ‘force vectoring’ which was previously observed in manoeuvres of other flying animals. In addition to force vectoring, we found that while flying backward, the dragonfly flaps its wings with larger angles of attack in the upstroke (US) when compared with forward flight. Also, the backward velocity of the body in the upright position enhances the wings' net velocity in the US. The combined effect of the angle of attack and wing net velocity yields large aerodynamic force generation in the US, with the average magnitude of the force reaching values as high as two to three times the body weight. Corresponding to these large forces was the presence of a strong leading edge vortex (LEV) at the onset of US which remained attached up until wing reversal. Finally, wing–wing interaction was found to enhance the aerodynamic performance of the hindwings (HW) during backward flight. Vorticity from the forewings’ trailing edge fed directly into the HW LEV to increase its circulation and enhance force production.

scholarly journals Lift and thrust generation by a butterfly-like flapping wing–body model: immersed boundary–lattice Boltzmann simulations

2015 ◽  
Vol 767 ◽  
pp. 659-695 ◽  
Author(s):  
Kosuke Suzuki ◽  
Keisuke Minami ◽  
Takaji Inamuro
Keyword(s):  
Lattice Boltzmann ◽  
Lift Force ◽  
Micro Air Vehicles ◽  
Flapping Wing ◽  
The Body ◽  
Immersed Boundary ◽  
Body Model ◽  
Lattice Boltzmann Simulations ◽  
Thrust Generation ◽  
Boltzmann Method

AbstractThe flapping flight of tiny insects such as flies or larger insects such as butterflies is of fundamental interest not only in biology itself but also in its practical use for the development of micro air vehicles (MAVs). It is known that a butterfly flaps downward for generating the lift force and backward for generating the thrust force. In this study, we consider a simple butterfly-like flapping wing–body model in which the body is a thin rod and the rectangular rigid wings flap in a simple motion. We investigate lift and thrust generation of the model by using the immersed boundary–lattice Boltzmann method. First, we compute the lift and thrust forces when the body of the model is fixed for Reynolds numbers in the range of 50–1000. In addition, we estimate the supportable mass for each Reynolds number from the computed lift force. Second, we simulate free flights when the body can only move translationally. It is found that the expected supportable mass can be supported even in the free flight except when the mass of the body relative to the mass of the fluid is too small, and the wing–body model with the mass of actual insects can go upward against the gravity. Finally, we simulate free flights when the body can move translationally and rotationally. It is found that the body has a large pitch motion and consequently gets off-balance. Then, we discuss a way to control the pitching angle by flexing the body of the wing–body model.

Actively flapping tandem flexible flags in a viscous flow

2015 ◽  
Vol 780 ◽  
pp. 120-142 ◽  
Author(s):  
Emad Uddin ◽  
Wei-Xi Huang ◽  
Hyung Jin Sung
Keyword(s):  
Viscous Flow ◽  
Immersed Boundary Method ◽  
Leading Edge ◽  
Underlying Mechanism ◽  
The Body ◽  
Immersed Boundary ◽  
Flexible Body ◽  
Flexible Bodies ◽  
Body Shapes ◽  
Heave Motion

The active flapping motions of fish and cetaceans generate both propulsive and manoeuvring forces. The tail fin motions of the majority of fish can essentially be viewed as a combined pitch-and-heave motion. Downstream bodies are strongly influenced by the vortices shed from an upstream body. To investigate the interactions between flexible bodies and vortices, the present study examined tandem flexible flags in a viscous flow by using an improved version of the immersed boundary method. The upstream flag underwent passive flapping in a uniform flow while the downstream flag flapped according to a prescribed pitching and heaving motion of the leading edge. The influences of the active flapping motion on the system dynamics were examined in detail, including the frequency, the phase angle, the bending coefficient and the amplitudes of the pitching and heaving motion. The variation of the drag coefficient of the downstream flag was explored together with the instantaneous vorticity contours and the body shapes. Both the slalom mode and the interception mode were identified according to the vortex–flexible body interactions, corresponding to the low- and high-drag situations, respectively. The underlying mechanism was discussed and compared with previous studies.

Lattice Boltzmann simulations of flapping wings: The flock effect and the lateral wind effect

2014 ◽  
Vol 25 (08) ◽  
pp. 1450031 ◽  
Author(s):  
Alessandro De Rosis
Keyword(s):  
Lattice Boltzmann ◽  
Threshold Value ◽  
Rigid Bodies ◽  
Body Motion ◽  
Critical Threshold ◽  
Immersed Boundary ◽  
Wind Effect ◽  
Lattice Boltzmann Simulations ◽  
Coupling Strategy ◽  
Biological Organisms

In this paper, numerical analysis aiming at simulating biological organisms immersed in a fluid are carried out. The fluid domain is modeled through the lattice Boltzmann (LB) method, while the immersed boundary method is used to account for the position of the organisms idealized as rigid bodies. The time discontinuous Galerkin method is employed to compute body motion. An explicit coupling strategy to combine the adopted numerical methods is proposed. The vertical take-off of a couple of butterflies is numerically simulated in different scenarios, showing the mutual interaction that a butterfly exerts on the other one. Moreover, the effect of lateral wind is investigated. A critical threshold value of the lateral wind is defined, thus corresponding to an increasing arduous take-off.

scholarly journals Tornado dynamics study using immersed boundary (IB) - Lattice Boltzmann Method (LBM) on a 7-cylinder building configuration

2021 ◽  
Author(s):  
Rangaraj Palanisamy
Keyword(s):  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Aerodynamic Force ◽  
Optimization Procedure ◽  
Immersed Boundary ◽  
Structure Interaction ◽  
Building Model ◽  
The Individual ◽  
Boltzmann Method ◽  
Safe Zones

Tornadoes are disastrous, naturally occurring atmospheric phenomena; they cause fatalities; they damage properties with an exceptional combination of translational and rotational velocities. Despite many studies on tornado-structure interaction, the research papers on tornado-multi-body interactions are limited. This research studies the effects of a tornadic wind on a 7-cylinder building model at several orientations in 2-D using a powerful Immersed Boundary-Lattice Boltzmann Method (IB-LBM). The tornadic wind was simulated by a customized Rankine Combined Vortex Model (RCVM). The wind-loadings on the seven cylinders were quantified using aerodynamic force and moment coefficients. The essential flow features associated with a vortex-structure interaction was investigated in great detail by doing a case study. Then, a unique optimization procedure was utilized to detect individual safe zones for each aerodynamic coefficient. Finally, an overall safe zone for the complete 7-cylinder building model has been ascertained to be between 29° and 69° by analyzing the individual safe zones.

Hydrodynamics and Flow Characterization of Tuna-Inspired Propulsion in Forward Swimming

2019 ◽  
Author(s):  
Junshi Wang ◽  
Huy Tran ◽  
Martha Christino ◽  
Carl White ◽  
Joseph Zhu ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Leading Edge ◽  
Underwater Vehicle ◽  
Numerical Approach ◽  
Primary Objective ◽  
Computational Effort ◽  
The Body ◽  
Hydrodynamic Performance ◽  
Immersed Boundary ◽  
Ring Structures

Abstract A combined experimental and numerical approach is employed to study the hydrodynamic performance and characterize the flow features of thunniform swimming by using a tuna-inspired underwater vehicle in forward swimming. The three-dimensional, time-dependent kinematics of the body-fin system of the underwater vehicle is obtained via a stereo-videographic technique. A high-fidelity computational model is then directly reconstructed based on the experimental data. A sharp-interface immersed-boundary-method (IBM) based incompressible flow solver is employed to compute the flow. The primary objective of the computational effort is to quantify the thrust performance of the model. The body kinematics and hydrodynamic performances are quantified and the dynamics of the vortex wake are analyzed. Results have shown significant leading-edge vortex at the caudal fin and unique vortex ring structures in the wake. The results from this work help to bring insight into understanding the thrust producing mechanism of thunniform swimming and to provide potential suggestions in improving the hydrodynamic performance of swimming underwater vehicles.

Immersed Boundary – Thermal Lattice Boltzmann Methods for Non-Newtonian Flows Over a Heated Cylinder: A Comparative Study

2015 ◽  
Vol 18 (2) ◽  
pp. 489-515 ◽  
Author(s):  
A. Amiri Delouei ◽  
M. Nazari ◽  
M. H. Kayhani ◽  
S. Succi
Keyword(s):  
Lattice Boltzmann ◽  
Computational Cost ◽  
Shear Thickening ◽  
The Body ◽  
Sharp Interface ◽  
Immersed Boundary ◽  
Heated Cylinder ◽  
Hydrodynamic Approach ◽  
Direct Forcing ◽  
Thermal Lattice Boltzmann

AbstractIn this study, we compare different diffuse and sharp interface schemes of direct-forcing immersed boundary — thermal lattice Boltzmann method (IB-TLBM) for non-Newtonian flow over a heated circular cylinder. Both effects of the discrete lattice and the body force on the momentum and energy equations are considered, by applying the split-forcing Lattice Boltzmann equations. A new technique based on predetermined parameters of direct forcing IB-TLBM is presented for computing the Nusselt number. The study covers both steady and unsteady regimes (20<Re<80) in the power-law index range of 0.6<n<1.4, encompassing both shear-thinning and shear-thickening non-Newtonian fluids. The numerical scheme, hydrodynamic approach and thermal parameters of different interface schemes are compared in both steady and unsteady cases. It is found that the sharp interface scheme is a suitable and possibly competitive method for thermal-IBM in terms of accuracy and computational cost.

The Design of Two Pendulums Spherical Robot

2013 ◽  
Vol 312 ◽  
pp. 741-744
Author(s):  
Shao Jun Ma
Keyword(s):  
Total Mass ◽  
Structural Model ◽  
Inertial Force ◽  
Moment Of Inertia ◽  
Robot Design ◽  
Mass Ratio ◽  
Spherical Robot ◽  
Drive Unit ◽  
The Moment ◽  
Main Components

A spherical robot driven by two pendulums is designed, which is actuated by both the eccentric force and the inertial force generated by the inner drive unit when the robot is in motion. This improved drive manner improve the eccentric mass ratio greater than the robot total mass, can provide more eccentric moment and the moment of inertia, so that the robot has a higher speed of movement, Through the analysis of movement principle and design to complete the structural model and the main components of the spherical robot design.

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