scispace - formally typeset
Book ChapterDOI

Probing into the Efficacy of Discrete Forcing Immersed Boundary Method in Capturing the Aperiodic Transition in the Wake of a Flapping Airfoil

01 Jan 2021-pp 271-281
Abstract: The present work focuses on investigating the underlying flow physics behind the transition from periodicity to aperiodicity in the flow past a harmonically plunging elliptic foil as the plunge amplitude is increased to a high value. Two-dimensional (2D) numerical simulations have been performed in the low Reynolds number regime using an in-house flow solver developed following the discrete forcing Immersed Boundary Method (IBM). To capture the aperiodic transition in the unsteady flow-field behind a flapping foil accurately, the boundary structures such as the leading-edge vortex and its evolution with time need to be resolved with maximum accuracy as they are the primary key to the manifestation of the aperiodic onset. Even a small discrepancy may result in a different dynamical state and lead to an erroneous prediction of the transition route. On the other hand, discrete forcing IBM is known to suffer from non-physical spurious oscillations of the velocity and pressure field near the boundary, which may affect the overall flow-field solution. In this regard, the present work investigates the efficacy of discrete forcing IBM in accurately capturing the transitional dynamics in the flow-field around a plunging elliptic foil by comparing its results with that of a well-validated body-fitted ALE solver. more

Topics: Immersed boundary method (55%), Reynolds number (52%), Vortex (51%) more
More filters

Journal ArticleDOI
Rajat Mittal1, Gianluca Iaccarino2Institutions (2)
TL;DR: The term immersed boundary (IB) method is used to encompass all such methods that simulate viscous flows with immersed (or embedded) boundaries on grids that do not conform to the shape of these boundaries. more

Abstract: The term “immersed boundary method” was first used in reference to a method developed by Peskin (1972) to simulate cardiac mechanics and associated blood flow. The distinguishing feature of this method was that the entire simulation was carried out on a Cartesian grid, which did not conform to the geometry of the heart, and a novel procedure was formulated for imposing the effect of the immersed boundary (IB) on the flow. Since Peskin introduced this method, numerous modifications and refinements have been proposed and a number of variants of this approach now exist. In addition, there is another class of methods, usually referred to as “Cartesian grid methods,” which were originally developed for simulating inviscid flows with complex embedded solid boundaries on Cartesian grids (Berger & Aftosmis 1998, Clarke et al. 1986, Zeeuw & Powell 1991). These methods have been extended to simulate unsteady viscous flows (Udaykumar et al. 1996, Ye et al. 1999) and thus have capabilities similar to those of IB methods. In this review, we use the term immersed boundary (IB) method to encompass all such methods that simulate viscous flows with immersed (or embedded) boundaries on grids that do not conform to the shape of these boundaries. Furthermore, this review focuses mainly on IB methods for flows with immersed solid boundaries. Application of these and related methods to problems with liquid-liquid and liquid-gas boundaries was covered in previous reviews by Anderson et al. (1998) and Scardovelli & Zaleski (1999). Consider the simulation of flow past a solid body shown in Figure 1a. The conventional approach to this would employ structured or unstructured grids that conform to the body. Generating these grids proceeds in two sequential steps. First, a surface grid covering the boundaries b is generated. This is then used as a boundary condition to generate a grid in the volume f occupied by the fluid. If a finite-difference method is employed on a structured grid, then the differential form of the governing equations is transformed to a curvilinear coordinate system aligned with the grid lines (Ferziger & Peric 1996). Because the grid conforms to the surface of the body, the transformed equations can then be discretized in the more

2,809 citations

Journal ArticleDOI
Jungwoo Kim1, Dongjoo Kim1, Haecheon Choi1Institutions (1)
Abstract: A new immersed-boundary method for simulating flows over or inside complex geometries is developed by introducing a mass source/sink as well as a momentum forcing. The present method is based on a finite-volume approach on a staggered mesh together with a fractional-step method. Both momentum forcing and mass source are applied on the body surface or inside the body to satisfy the no-slip boundary condition on the immersed boundary and also to satisfy the continuity for the cell containing the immersed boundary. In the immersed-boundary method, the choice of an accurate interpolation scheme satisfying the no-slip condition on the immersed boundary is important because the grid lines generally do not coincide with the immersed boundary. Therefore, a stable second-order interpolation scheme for evaluating the momentum forcing on the body surface or inside the body is proposed. Three different flow problems (decaying vortices and flows over a cylinder and a sphere) are simulated using the immersed-boundary method proposed in this study and the results agree very well with previous numerical and experimental results, verifying the accuracy of the present method. more

987 citations

Journal ArticleDOI
Manoochehr Koochesfahani1Institutions (1)
24 Mar 1987-AIAA Journal
Abstract: The vortical flow patterns in the wake of a NACA 0012 airfoil pitching at small amplitudes are studied in a low speed water channel. it is shown that a great deal of control can be exercised on the structure of the wake by the control of the frequency, amplitude and also the shape of the oscillation waveform. An important observation in this study has been the existence of an axial flow along the cores of the wake vortices. Estimates of the magnitude of the axial flow suggest a linear dependence on the oscillation frequency and amplitude. more

619 citations


Journal ArticleDOI
TL;DR: This article reviews representative numeri- cal methods based on conforming and non-conforming meshes that are currently avail- able for computing fluid-structure interaction problems, with an emphasis on some of the recent developments in the field. more

Abstract: The interactions between incompressible fluid flows and immersed struc- tures are nonlinear multi-physics phenomena that have applications to a wide range of scientific and engineering disciplines In this article, we review representative numeri- cal methods based onconforming and non-conforming meshes that arecurrentlyavail- able for computing fluid-structure interaction problems, with an emphasis on some of the recent developments in the field A goal is to categorize the selected methods and assess their accuracy and efficiency We discuss challenges faced by researchers in this field, and we emphasize the importance of interdisciplinary effort for advancing the study in fluid-structure interactions more

469 citations

Journal ArticleDOI
01 Jan 1998-AIAA Journal
Abstract: The ability of a sinusoidally plunging airfoil to produce thrust, known as the Knoller-Betz or Katzmayr effect, is investigated experimentally and numerically. Water-tunnel experiments are performed providing flow visualization and laser Doppler velocimetry data of the unsteady wakes formed by the plunging foils. Vortical structures and time-averaged velocity profiles in the wake are compared with numerical computations from a previously developed inviscid, unsteady panel code that utilizes a nonlinear wake model more

375 citations