A novel 3D variational aeroelastic framework for flexible multibody dynamics: Application to bat-like flapping dynamics

Li, G.; Law, Yun Zhi; Jaiman, Rajeev K.

doi:10.1016/j.compfluid.2018.11.013

Cited by 21 publications

(9 citation statements)

References 55 publications

(82 reference statements)

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“…To avoid the numerical instability caused by significant added mass effect, a recently developed nonlinear interface force correction scheme (Jaiman, Pillalamarri & Guan 2016) is used to correct and stabilize the fluid forces at each iterative step. The fluid–multibody structure interaction equations and the variational partitioned formulations for the fluid–structure interaction framework have been described by Li, Law & Jaiman (2019) in detail. This fluid–structure interaction solver has been validated for an anisotropic flexible wing with supporting battens and covered membrane components (Li et al.…”

Section: Numerical Methodologymentioning

confidence: 99%

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Flow-excited membrane instability at moderate Reynolds numbers

Jaiman

Khoo

2021

J. Fluid Mech.

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In this paper, we study the fluid–structure interaction of a three-dimensional (3-D) flexible membrane immersed in an unsteady separated flow at moderate Reynolds numbers. We employ a body-conforming variational fluid–structure interaction solver based on the recently developed partitioned iterative scheme for the coupling of turbulent fluid flow with nonlinear structural dynamics. Of particular interest is to understand the flow-excited instability of a 3-D flexible membrane as a function of the non-dimensional mass ratio ( $m^{*}$ ), Reynolds number ( $Re$ ) and aeroelastic number ( $Ae$ ). For a wide range of parameters, we examine two distinct stability regimes of the fluid–membrane interaction: deformed steady state (DSS) and dynamic balance state (DBS). We propose stability phase diagrams to demarcate the DSS and DBS regimes for the parameter space of mass ratio versus Reynolds number ( $m^{*}$ - $Re$ ) and mass ratio versus aeroelastic number ( $m^{*}$ - $Ae$ ). With the aid of the global Fourier mode decomposition technique, the distinct dominant vibrational modes are identified from the intertwined membrane responses in the parameter space of $m^{*}$ - $Re$ and $m^{*}$ - $Ae$ . Compared to the deformed steady membrane, the flow-excited vibration produces relatively longer attached leading-edge vortices which improve the aerodynamic performance when the coupled system is near the flow-excited instability boundary. The optimal aerodynamic performance is achieved for lighter membranes with higher $Re$ and larger flexibility. Based on the global aeroelastic mode analysis, we observe a frequency lock-in phenomenon between the vortex-shedding frequency and the membrane vibration frequency causing self-sustained vibrations in the dynamic balance state. To characterize the origin of the frequency lock-in, we propose an approximate analytical formula for the nonlinear natural frequency by considering the added mass effect and employing a large deflection theory for a simply supported rectangular membrane. Through our systematic high-fidelity numerical investigation, we find that the onset of the membrane vibration and the mode transition has a direct dependence on the frequency lock-in between the natural frequency of the tensioned membrane and the vortex-shedding frequency or its harmonics. These findings on the fluid-elastic instability of membranes have implications for the design and development of control strategies for membrane wing-based unmanned systems and drones.

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Section: Numerical Methodologymentioning

confidence: 99%

“…This fluid–structure interaction solver has been validated for an anisotropic flexible wing with supporting battens and covered membrane components (Li et al. 2019).…”

Section: Numerical Methodologymentioning

confidence: 99%

Flow-excited membrane instability at moderate Reynolds numbers

Jaiman

Khoo

2021

J. Fluid Mech.

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“…Fluid-structure interaction (FSI) is a coupled highly-nonlinear multiphysics problem that can be found in various natural phenomena and industrial processes. Examples include from traditional aeroelasticity and flow-induced vibration problems in aerospace engineering [1,2,3,4], marine/offshore [5,6,7,8], biomedical [9,10,11], energy harvesting [12] to the emerging fields of muscular hydrostat [13,14] and soft robotics [15] and bio-inspired flying vehicles [16]. The interface between the fluid and solid poses significant challenges in mathematical modeling and numerical simulation [17,18].…”

Section: Introductionmentioning

confidence: 99%

An interface and geometry preserving phase-field method for fully Eulerian fluid-structure interaction

Mao¹,

Jaiman²

2022

Preprint

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We present an interface and geometry preserving (IGP) method for the modeling of fully Eulerian fluid-structure interaction via phase-field formulation. While the hyperbolic tangent interface profile is preserved by the time-dependent mobility model, the proposed method maintains the geometry of the solid-fluid interface by reducing the volume-conserved mean curvature flow. To achieve the reduction in the curvature flow, we construct a gradient-minimizing velocity field (GMV) for the convection of the order parameter. The constructed velocity field enables the preservation of the solid velocity in the solid domain while extending the velocity in the normal direction throughout the diffuse interface region. With this treatment, the GMV reduces the normal velocity difference of the level sets of the order parameter which alleviates the undesired thickening or thinning of the diffuse interface region due to the convection. During this process, the time-dependent mobility coefficient is substantially reduced and there is a lesser volume-conserved mean curvature flow. The GMV ensures that the diffuse interface region moves with the solid bulk such that the fluid-solid interface conforms to the geometry of the solid. Using the unified momentum equation and the phase-dependent interpolation, we integrate the IGP method into a fully Eulerian variational FSI solver based on the incompressible viscous fluid and the neo-Hookean solid. We first demonstrate the ability of the phase-field-based IGP method for the convection of circular and square interfaces with a prescribed velocity field. The variational FSI framework with the IGP method is then examined for the flow passing a fixed deformable block in a channel domain. Finally, the vibration of a plate attached behind a stationary cylinder subjected to incoming flow is employed to assess the fully Eulerian framework for a large aspect ratio and sharp corners.

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“…22 On the other hand, there are studies with the assumption of neglecting forces and moments generated by the insect's body compared to that of the flapping wing. [23][24][25][26][27][28] This assumption is only valid in the case of hovering flight, in which the contribution of body aerodynamics is insignificant. However, as the flight speed increases the wing-body interaction tends to enhance the lift dramatically.…”

Section: Introductionmentioning

confidence: 99%

Multi-physics simulation of an insect with flapping wings

Bakhshaei

MoradiMaryamnegari

SalavatiDezfouli

et al. 2020

Proceedings of the Institution of Mechanical Engineers, Part G:

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In this paper, the unsteady aerodynamic of an insect’s forward flight has been carried out with a novel approach. In order to fully utilize the available powerful solvers, an innovative intermediary MATLAB code has been written for the high-fidelity time-resolved multi-physics problems involving fluid flow and multi-body simulations. For simulating the insect’s flight, the FLUENT solver has been utilized to determine aerodynamic forces and moments of the wings and main body while ADAMS software has been employed to calculate translational and angular velocities. Overset grid technology accompanied with dynamic mesh method have been implemented for the movement of the insect. The code is responsible for the synchronization of the solvers at the end of each time step as well as the integration of the solutions. Three different simulations are done for two different insects’ geometries. For the first and second simulations, a simplified geometry of an insect is selected, due to the ease of manufacturing and testing. At first, all rotational and translational degrees of freedom are considered to be free. The motion path history shows the instability due to an inappropriate location of the center of gravity. Hence, in the second case, it is assumed that the insect’s main body is limited to the vertical motion. In the final simulation, a complicated model of a bee with exact geometry and wings kinematics extracts from the experimental data with the free translational degrees of freedom. According to the results, combining multiple software in which they can interact with each other at each time step, is the most accurate way for doing precise multi-physics simulations.

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A novel 3D variational aeroelastic framework for flexible multibody dynamics: Application to bat-like flapping dynamics

Cited by 21 publications

References 55 publications

Flow-excited membrane instability at moderate Reynolds numbers

Flow-excited membrane instability at moderate Reynolds numbers

An interface and geometry preserving phase-field method for fully Eulerian fluid-structure interaction

Multi-physics simulation of an insect with flapping wings

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