Passive Pitch Mechanics of Elastic Flapping Wings

2018 ◽  
Author(s):  
Mark A. Jankauski
Keyword(s):  
Rigid Body ◽  
Aerodynamic Force ◽  
Joint Stiffness ◽  
Coupled Model ◽  
Micro Air Vehicles ◽  
Flexible Wings ◽  
Elastic Forces ◽  
Element Approach ◽  
Body Inertia ◽  
Blade Element

Many flapping wing micro air vehicles (FWMAVs) utilize a flexible joint that allows the wing to passively rotate about the pitching axis. Generally, simple rigid body models are used to estimate the passive pitching dynamics. However, evidence suggests elastic wings increase aerodynamic force generation and expend less energy relative to rigid wings. As a result, elastic wings are becoming an integral part of FWMAV design. But, the effect of wing elasticity on passive pitching mechanics is unclear. To explore this, we develop a coupled model of an elastic wing attached to a flexible pitching joint. Aerodynamic moments are included through a simple blade element approach. The model is applied to an idealized insect forewing subject to prescribed roll rotation. The simulation results suggest (1) aerodynamic moments, not rigid body inertia or elastic forces, are primarily responsible for lift-generating passive pitch, (2) joint stiffness influences pitching mechanics more than wing elasticity does, and (3) flexible wings can increase net lift by as much as 20% if the pitching joint is mistuned. The framework developed in this paper can be used to design and optimize FWMAV systems in terms of both elastic wings and flexible passive pitch joints.

An Investigation on the Issues in Modelling of Free Flight in Animal Locomotion

2011 ◽  
Author(s):  
Masateru Maeda ◽  
Toshiyuki Nakata ◽  
Hao Liu
Keyword(s):  
Rigid Body ◽  
Degrees Of Freedom ◽  
Aerodynamic Force ◽  
Three Dimensional ◽  
Micro Air Vehicles ◽  
Rigid Body Dynamics ◽  
Free Flight ◽  
Comprehensive Investigation ◽  
Body Dynamics ◽  
Generation Mechanisms

Aiming at establishing an effective computational framework to accurately predict free-flying dynamics and aerodynamics we here present a comprehensive investigation on some issues associated with the modelling of free flight. Free flight modelling/simulation is essential for some types of flights e.g. falling leaves or auto-rotating seeds for plants; unsteady manoeuvres such as take-off, turning, or landing for animals. In addition to acquiring the deeper understanding of the flight biomechanics of those natural organisms, revealing the sophisticated aerodynamic force generation mechanisms employed by them may be useful in designing man-made flying-machines such as rotary or flapping micro air vehicles (MAVs). The simulations have been conducted using the coupling of computational fluid dynamics (CFD) and rigid body dynamics, thus achieving the free flight. The flow field is computed with a three-dimensional unsteady incompressible Navier-Stokes solver using pseudo-compressibility and overset gird technique. The aerodynamic forces acting on the flyer are calculated by integrating the forces on the surfaces. Similarly, the aerodynamic torque around the flyer’s centre of mass is obtained. The forces and moments are then introduced into a six degrees-of-freedom rigid body dynamics solver which utilises unit quaternions for attitude description in order to avoid singular attitude. Results are presented of a single body model and some insect-like multi-body models with flapping wings, which point to the importance of free-flight modelling in systematic analyses of flying aerodynamics and manoeuvrability. Furthermore, a comprehensive investigation indicates that the framework is capable to predict the aerodynamic performance of free-flying or even free-swimming animals in an intermediate range of Reynolds numbers (< 105).

Rigid Body Inertia Properties

2021 ◽  
Vol 63 (9) ◽  
pp. 1483-1489
Author(s):  
T. B. Goldvarg ◽  
V. N. Shapovalov
Keyword(s):  
Rigid Body ◽  
Inertia Properties ◽  
Body Inertia

Methodology Development for Simulating Full Frontal and Offset Frontal Impacts Using Full Vehicle MADYMO Models

1999 ◽  
Author(s):  
Bala Deshpande ◽  
Gunasekar TJ ◽  
Russell Morris ◽  
Sudhanshu Parida ◽  
Mostafa Rashidy ◽  
...  
Keyword(s):  
Rigid Body ◽  
Joint Stiffness ◽  
Side Impact ◽  
Computational Time ◽  
Test Results ◽  
Vehicle Interior ◽  
Significant Saving ◽  
Methodology Development ◽  
Full Vehicle ◽  
Frontal Impacts

Abstract MADYMO articulated full vehicle models of the 1992 Ford Taurus, 1995 Chevrolet Lumina and the 1994 Dodge Intrepid for frontal and side impact modes have been developed and validated against test data. MADYMO (Mathematical Dynamic Model) is typically used to model occupants in the environment of the vehicle interior and thus finds application mainly in assessing occupant injuries. In this study however, MADYMO has been employed not only to model the occupants but also to represent the major load bearing structures in the vehicles. Input for the MADYMO models consisting of rigid body joint stiffness was obtained from corresponding full vehicle Finite Element (FE) models. Model validation was done by comparing the vehicle and dummy numbers with the New Car Assessment Program (NCAP) test results. Models correlated very well with both test and FE data. This modeling approach demonstrates the utility of rigid body based full car models for crashworthiness analysis. Such models result in significant saving in computational time and resources. In this paper, we describe the simulation of two different crash modes: full frontal and offset frontal impacts using the full vehicle MADYMO models. These simulations were validated with the corresponding test results in full frontal mode and IIHS offset mode. The models are useful for simulating a variety of impact situations, for example, with different occupant sizes, occupant positions, impact velocities, and in car to car impacts for performing compatibility studies.

Deformable Blade Element and Unsteady Vortex Lattice Fluid-Structure Interaction Modeling of a 2D Flapping Wing

2020 ◽  
Author(s):  
Joseph Reade ◽  
Mark A. Jankauski
Keyword(s):  
Vortex Lattice ◽  
Normal Force ◽  
Aerodynamic Force ◽  
Fluid Structure Interaction ◽  
Force Production ◽  
Flapping Wing ◽  
Energetic Efficiency ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Blade Element

Abstract Flapping insect wings experience appreciable deformation due to aerodynamic and inertial forces. This deformation is believed to benefit the insect’s aerodynamic force production as well as energetic efficiency. However, the fluid-structure interaction (FSI) models used to estimate wing deformations are often computationally demanding and are therefore challenged by parametric studies. Here, we develop a simple FSI model of a flapping wing idealized as a two-dimensional pitching-plunging airfoil. Using the Lagrangian formulation, we derive the reduced-order structural framework governing wing’s elastic deformation. We consider two fluid models: quasi-steady Deformable Blade Element Theory (DBET) and Unsteady Vortex Lattice Method (UVLM). DBET is computationally economical but does not provide insight into the flow structure surrounding the wing, whereas UVLM approximates flows but requires more time to solve. For simple flapping kinematics, DBET and UVLM produce similar estimates of the aerodynamic force normal to the surface of a rigid wing. More importantly, when the wing is permitted to deform, DBET and UVLM agree well in predicting wingtip deflection and aerodynamic normal force. The most notable difference between the model predictions is a roughly 20° phase difference in normal force. DBET estimates wing deformation and force production approximately 15 times faster than UVLM for the parameters considered, and both models solve in under a minute when considering 15 flapping periods. Moving forward, we will benchmark both low-order models with respect to high fidelity computational fluid dynamics coupled to finite element analysis, and assess the agreement between DBET and UVLM over a broader range of flapping kinematics.

Numerical Simulation of Micro Air Vehicles With Membrane Wings

2007 ◽  
Author(s):  
Xiaoqin Zhang ◽  
Ling Tian
Keyword(s):  
Numerical Simulation ◽  
Pressure Distribution ◽  
Micro Air Vehicles ◽  
Flexible Wings ◽  
Design Modification ◽  
Structure Deformation ◽  
Flexible Wing ◽  
Fluid Field ◽  
Distributed Pressure ◽  
Air Vehicles

Micro Air Vehicles (MAVs) have advantages of small size, low cost, flexibility and controllability etc., so they will be applied widely in military and civilian fields. They have obviously low Reynolds number aerodynamics, which is different from traditional aircrafts. In this paper, numerical simulation based on fluid-structure interaction for flexible wing MAVs is presented. Flexible wings are composed of carbon frames and covered with membrane skins. Because flexible wing MAVs easily deform in airflow, both structure model and fluid model should be built. The two models are connected by interfaces of membrane wings, which transmit distributed pressure and deformations of membrane wings. When membrane wings are located in airflow, they will deform with actions of surrounding airflow. Deformation of membrane wings also affects airflow and pressure distributed on the wings’ surfaces will also be changed relatively, which will compel the shape of membrane wings to be changed once more. Therefore, numerical simulation of flexible wing MAVs is not only the analysis of fluid field, but also the structure deformation effects. Navier-Stokes Equations are nonlinear and complicated, so direct interaction of fluid and structure equations is rather difficult and costs too much time. Indirect interaction method is more feasible and it is adopted in this paper. Structure deformation and distributed pressure on membrane wings surfaces are calculated separately, and then pressure distribution from fluid solver is transmitted to structure solver. After structure deformation is calculated in structure solver, it will be transmitted to fluid field again. Iteration goes on in this way and finally converges. Simulation results show the deformation, stress and pressure distribution of flexible wings. All these results are good reference for MAVs design, modification and wind tunnel experiments generally.

scholarly journals Stochastic Model for Aerodynamic Force Dynamics on Wind Turbine Blades in Unsteady Wind Inflow

2015 ◽  
Vol 10 (4) ◽  
Author(s):  
M. R. Luhur ◽  
J. Peinke ◽  
M. Kühn ◽  
M. Wächter
Keyword(s):  
Stochastic Model ◽  
Wind Turbine ◽  
Aerodynamic Force ◽  
Turbine Blades ◽  
Stochastic Approach ◽  
Simulation Software ◽  
Dynamic Stall ◽  
Wind Turbine Blades ◽  
Full Field ◽  
Blade Element

The paper presents a stochastic approach to estimate the aerodynamic forces with local dynamics on wind turbine blades in unsteady wind inflow. This is done by integrating a stochastic model of lift and drag dynamics for an airfoil into the aerodynamic simulation software AeroDyn. The model is added as an alternative to the static table lookup approach in blade element momentum (BEM) wake model used by AeroDyn. The stochastic forces are obtained for a rotor blade element using full field turbulence simulated wind data input and compared with the classical BEM and dynamic stall models for identical conditions. The comparison shows that the stochastic model generates additional extended dynamic response in terms of local force fluctuations. Further, the comparison of statistics between the classical BEM, dynamic stall, and stochastic models' results in terms of their increment probability density functions (PDFs) gives consistent results.

A predictive quasi-steady model of aerodynamic loads on flapping wings

2016 ◽  
Vol 800 ◽  
pp. 688-719 ◽  
Author(s):  
Q. Wang ◽  
J. F. L. Goosen ◽  
F. van Keulen
Keyword(s):  
Aerodynamic Force ◽  
Micro Air Vehicles ◽  
Mass Effect ◽  
Reynolds Numbers ◽  
Flapping Wings ◽  
Accurate Estimation ◽  
Pitching Motion ◽  
Aerodynamic Loads ◽  
Design And Optimization ◽  
Aerodynamic Torque

Quasi-steady aerodynamic models play an important role in evaluating aerodynamic performance and conducting design and optimization of flapping wings. The kinematics of flapping wings is generally a resultant motion of wing translation (yaw) and rotation (pitch and roll). Most quasi-steady models are aimed at predicting the lift and thrust generation of flapping wings with prescribed kinematics. Nevertheless, it is insufficient to limit flapping wings to prescribed kinematics only since passive pitching motion is widely observed in natural flapping flights and preferred for the wing design of flapping wing micro air vehicles (FWMAVs). In addition to the aerodynamic forces, an accurate estimation of the aerodynamic torque about the pitching axis is required to study the passive pitching motion of flapping flights. The unsteadiness arising from the wing’s rotation complicates the estimation of the centre of pressure (CP) and the aerodynamic torque within the context of quasi-steady analysis. Although there are a few attempts in literature to model the torque analytically, the involved problems are still not completely solved. In this work, we present an analytical quasi-steady model by including four aerodynamic loading terms. The loads result from the wings translation, rotation, their coupling as well as the added-mass effect. The necessity of including all the four terms in a quasi-steady model in order to predict both the aerodynamic force and torque is demonstrated. Validations indicate a good accuracy of predicting the CP, the aerodynamic loads and the passive pitching motion for various Reynolds numbers. Moreover, compared to the existing quasi-steady models, the presented model does not rely on any empirical parameters and thus is more predictive, which enables application to the shape and kinematics optimization of flapping wings.

Finite Element Incremental Approach and Exact Rigid Body Inertia

1996 ◽  
Vol 118 (2) ◽  
pp. 171-178 ◽  
Author(s):  
A. A. Shabana
Keyword(s):  
Finite Element ◽  
Rigid Body ◽  
Rigid Bodies ◽  
Simple Expression ◽  
Shape Functions ◽  
Large Rotation ◽  
Nodal Coordinates ◽  
Inertia Properties ◽  
Element Shape ◽  
Body Inertia

In the dynamics of multibody systems that consist of interconnected rigid and deformable bodies, it is desirable to have a formulation that preserves the exactness of the rigid body inertia. As demonstrated in this paper, the incremental finite element approach, which is often used to solve large rotation problems, does not lead to the exact inertia of simple structures when they rotate as rigid bodies. Nonetheless, the exact inertia properties, such as the mass moments of inertia and the moments of mass, of the rigid bodies can be obtained using the finite element shape functions that describe large rigid body translations by introducing an intermediate element coordinate system. The results of application of the parallel axis theorem can be obtained using the finite element shape functions by simply changing the element nodal coordinates. As demonstrated in this investigation, the exact rigid body inertia properties in case of rigid body rotations can be obtained using the shape function if the nodal coordinates are defined using trigonometric functions. The analysis presented in this paper also demonstrates that a simple expression for the kinetic energy can be obtained for flexible bodies that undergo large displacements without the need for interpolation of large rotation coordinates.

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