Flow physics and dynamics of flow-induced pitch oscillations of an airfoil

2019 ◽  
Vol 877 ◽  
pp. 582-613 ◽  
Author(s):  
Karthik Menon ◽  
Rajat Mittal
Keyword(s):  
Immersed Boundary Method ◽  
Energy Exchange ◽  
Computational Study ◽  
Immersed Boundary ◽  
Two Dimensional ◽  
Spring Stiffness ◽  
Simulation Data ◽  
Complex Behaviour ◽  
Equilibrium Angle ◽  
Complex Phenomena

We conduct a computational study of flow-induced pitch oscillations of a rigid airfoil at a chord-based Reynolds number of 1000. A sharp-interface immersed boundary method is used to simulate two-dimensional incompressible flow, and this is coupled with the equations for a rigid foil supported at the elastic axis with a linear torsional spring. We explore the effect of spring stiffness, equilibrium angle-of-attack and elastic-axis location on the onset of flutter, and the analysis of the simulation data provides insights into the time scales and mechanisms that drive the onset and dynamics of flutter. The dynamics of this configuration includes complex phenomena such as bifurcations, non-monotonic saturation amplitudes, hysteresis and non-stationary limit-cycle oscillations. We show the utility of ‘maps’ of energy exchange between the flow and the airfoil system, as a way to understand, and even predict, this complex behaviour.

Level set-based topology optimization for two dimensional turbulent flow using an immersed boundary method

2021 ◽  
pp. 110630
Author(s):  
Seiji Kubo ◽  
Atsushi Koguchi ◽  
Kentaro Yaji ◽  
Takayuki Yamada ◽  
Kazuhiro Izui ◽  
...  
Keyword(s):  
Topology Optimization ◽  
Turbulent Flow ◽  
Level Set ◽  
Immersed Boundary Method ◽  
Immersed Boundary ◽  
Two Dimensional ◽  
Boundary Method

Two-dimensional compact finite difference immersed boundary method

2011 ◽  
Vol 65 (6) ◽  
pp. 609-624 ◽  
Author(s):  
Paulo J. S. A. Ferreira de Sousa ◽  
José C. F. Pereira ◽  
James J. Allen
Keyword(s):  
Finite Difference ◽  
Immersed Boundary Method ◽  
Immersed Boundary ◽  
Two Dimensional ◽  
Compact Finite Difference ◽  
Boundary Method

scholarly journals Three-dimensional simulation for fast forward flight of a calliope hummingbird

2016 ◽  
Vol 3 (6) ◽  
pp. 160230 ◽  
Author(s):  
Jialei Song ◽  
Bret W. Tobalske ◽  
Donald R. Powers ◽  
Tyson L. Hedrick ◽  
Haoxiang Luo
Keyword(s):  
Immersed Boundary Method ◽  
High Speed ◽  
Computational Study ◽  
Three Dimensional ◽  
The Body ◽  
Immersed Boundary ◽  
Forward Flight ◽  
Advance Ratio ◽  
Dimensional Simulation ◽  
Thrust Production

We present a computational study of flapping-wing aerodynamics of a calliope hummingbird ( Selasphorus calliope ) during fast forward flight. Three-dimensional wing kinematics were incorporated into the model by extracting time-dependent wing position from high-speed videos of the bird flying in a wind tunnel at 8.3 m s −1 . The advance ratio, i.e. the ratio between flight speed and average wingtip speed, is around one. An immersed-boundary method was used to simulate flow around the wings and bird body. The result shows that both downstroke and upstroke in a wingbeat cycle produce significant thrust for the bird to overcome drag on the body, and such thrust production comes at price of negative lift induced during upstroke. This feature might be shared with bats, while being distinct from insects and other birds, including closely related swifts.

Numerical Simulation of Unsteady Flow Through a Two-Dimensional Channel With a Vocal Cord Model

2011 ◽  
Author(s):  
Suguru Miyauchi ◽  
Takeshi Omori ◽  
Shintaro Takeuchi ◽  
Takeo Kajishima
Keyword(s):  
Vocal Cord ◽  
Immersed Boundary Method ◽  
Fluid Structure Interaction ◽  
Computational Method ◽  
Immersed Boundary ◽  
Two Dimensional ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Boundary Method ◽  
Flow Through

For the understanding of the phonation mechanism and for the design of an artificial vocal cord, we developed a computational method for the fluid-structure interaction, including the elastic walls and membranes. A robust and efficient method is required to deal with large deformation of biological materials and high frequency vibration. To this end, we apply an immersed boundary method. The flow through a two-dimensional channel including a pair of flexible structures, which is a simplification of a vocal cord, is simulated. The elastic solid is modeled by the St. Venant-Kirchhoff constitutive equation and its motion is simulated by a finite-element method, where the contact of the vocal cord is taken into account by a Lagrange multiplier method. The incompressible fluid flow is computed by a finite-difference method. Then the immersed-boundary method of a body-force type developed by the authors is successfully applied for the fluid-structure interaction. In the present results, the deformation of the structure and the frequency of the pulsating flow are reasonably reproduced. The obtained frequency is within the measured range of the data for a human vocal cord. Also, two velocity peaks are observed when the vocal cord is in the opening and closing phases in each period of the vocal cord vibration, and the velocity of the closing phase is larger than that of the opening phase.

The Immersed Boundary Method for Two-Dimensional Foam with Topological Changes

2012 ◽  
Vol 12 (2) ◽  
pp. 479-493 ◽  
Author(s):  
Yongsam Kim ◽  
Yunchang Seol ◽  
Ming-Chih Lai ◽  
Charles S. Peskin
Keyword(s):  
Immersed Boundary Method ◽  
Higher Order ◽  
Dimensional Case ◽  
Immersed Boundary ◽  
Two Dimensional ◽  
Triple Junctions ◽  
Von Neumann ◽  
Total Shrinkage ◽  
Ib Method ◽  
Topological Changes

AbstractWe extend the immersed boundary (IB) method to simulate the dynamics of a 2D dry foam by including the topological changes of the bubble network. In the article [Y. Kim, M.-C. Lai, and C. S. Peskin, J. Comput. Phys. 229:5194-5207,2010], we implemented an IB method for the foam problem in the two-dimensional case, and tested it by verifying the von Neumann relation which governs the coarsening of a two-dimensional dry foam. However, the method implemented in that article had an important limitation; we did not allow for the resolution of quadruple or higher order junctions into triple junctions. A total shrinkage of a bubble with more than four edges generates a quadruple or higher order junction. In reality, a higher order junction is unstable and resolves itself into triple junctions. We here extend the methodology previously introduced by allowing topological changes, and we illustrate the significance of such topological changes by comparing the behaviors of foams in which topological changes are allowed to those in which they are not.

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