Boundary data immersion method for Cartesian-grid simulations of fluid-body interaction problems

Weymouth, Gabriel; Yue, Dick K. P.

doi:10.1016/j.jcp.2011.04.022

Cited by 116 publications

(65 citation statements)

References 26 publications

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“…The Boundary Data Immersion Method (BDIM), a robust immersed boundary method suitable for dynamic fluid-structure interaction problems detailed in Weymouth & Yue (2011) and Maertens & Weymouth (2015), was used for this purpose. Briefly, the full Navier-Stokes equations and the prescribed body kinematics shown in figure 1 are convolved with a kernel of support = 2h, where h is the grid spacing.…”

Section: Methodsmentioning

confidence: 99%

Unsteady dynamics of rapid perching manoeuvres

2015

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A perching bird is able to rapidly decelerate while maintaining lift and control, but the underlying aerodynamic mechanism is poorly understood. In this work we perform a study on a simultaneously decelerating and pitching aerofoil section to increase our understanding of the unsteady aerodynamics of perching. We first explore the problem analytically, developing expressions for the added-mass and circulatory forces arising from boundary-layer separation on a flat-plate aerofoil. Next, we study the model problem through a detailed series of experiments at Re = 22000 and two-dimensional simulations at Re = 2000. Simulated vorticity fields agree with particle image velocimetry measurements, showing the same wake features and vorticity magnitudes. Peak lift and drag forces during rapid perching are measured to be more than 10 times the quasi-steady values. The majority of these forces can be attributed to added-mass energy transfer between the fluid and aerofoil, and to energy lost to the fluid by flow separation at the leading and trailing edges. Thus, despite the large angles of attack and decreasing flow velocity, this simple pitch-up manoeuvre provides a means through which a perching bird can maintain high lift and drag simultaneously while slowing to a controlled stop.

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Section: Methodsmentioning

confidence: 99%

Unsteady dynamics of rapid perching manoeuvres

2015

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“…The computational fluid dynamics (CFD) tool that was used is called LilyPad (Weymouth 2015), which solves the full two-dimensional Navier-Stokes equations by applying the Boundary Data Immersion Method (BDIM) as developed by Weymouth & Yue (2011). This method allows the solid and fluid domains to be combined analytically by using the general integration kernel formulation, resulting in a combined set of equations for the whole domain (Weymouth & Yue 2011).…”

Section: Computational Setupmentioning

confidence: 99%

“…This method allows the solid and fluid domains to be combined analytically by using the general integration kernel formulation, resulting in a combined set of equations for the whole domain (Weymouth & Yue 2011). Far less computing power is required to solve the equations compared to the original two-domain problem, so fast and accurate solutions can be obtained.…”

Section: Computational Setupmentioning

confidence: 99%

Performance augmentation mechanism of in-line tandem flapping foils

2017

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The propulsive performance of a pair of tandem flapping foils is sensitively dependent on the spacing and phasing between them. Large increases in thrust and efficiency of the hind foil are possible, but the mechanisms governing these enhancements remain largely unresolved. Two-dimensional numerical simulations of tandem and single foils oscillating in heave and pitch at a Reynolds number of 7,000 are performed over a broad and dense parameter space, allowing the effects of inter-foil spacing (S) and phasing (ϕ) to be investigated over a range of non-dimensional frequencies (or Strouhal number, St). Results indicate that the hind foil can produce from no thrust, to twice the thrust of a single foil depending on its spacing and phasing with respect to the fore foil, which is consistent with previous studies that were carried out over a limited parameter space. Examination of instantaneous flowfields indicate that high thrust occurs when the hind foil weaves in between the vortices that have been shed by the fore foil, and low thrust occurs when the hind foil intercepts these vortices. Contours of high thrust and minimal thrust appear as inclined bands in the S − ϕ parameter space and this behaviour is apparent over the entire range of Strouhal numbers considered (0.2 St 0.5). A novel quasi-steady model that utilises kinematics of a virtual hind foil together with data obtained from simulations of a single flapping foil shows that performance augmentation is primarily determined through modification of the instantaneous angle of attack of the hind foil by the vortex street established by the fore foil. This simple model provides estimates of thrust and efficiency for the hind foil, which is consistent with data obtained through full simulations. The limitations of the virtual hind foil method and its physical significance is also discussed.

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“…Simulations were performed using the boundary data immersion method, a robust immersed boundary method implemented on a Cartesian-grid, specifically developed for fluid-body interactions (Weymouth & Yue 2011;Maertens & Weymouth 2015). The method is well validated for foils with very similar grid spacing and resolution (Maertens & Weymouth 2015), as well as dynamic deforming bodies , 2013.…”

Section: Numerical Methodologymentioning

confidence: 99%

“…The energy recovery in a deflating body was demonstrated experimentally by Weymouth et al (2015), where an octopus-like robot undergoing deflation to propel itself also recovers its added mass energy, providing a high final escape speed.…”

Section: Introductionmentioning

confidence: 99%

Shape of retracting foils that model morphing bodies controls shed energy and wake structure

et al. 2016

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The flow mechanisms of shape-changing moving bodies are investigated through the simple model of a foil that is rapidly retracted over a spanwise distance as it is towed at constant angle of attack. It is shown experimentally and through simulation that by altering the shape of the tip of the retracting foil, different shape-changing conditions may be reproduced, corresponding to: (a) a vanishing body, (b) a deflating body, and (c) a melting body. A sharp-edge, 'vanishing-like' foil manifests strong energy release to the fluid; however it is accompanied by an additional release of energy, resulting in the formation of a strong ring vortex at the sharp tip edges of the foil during the retracting motion. This additional energy release introduces complex and quickly-evolving vortex structures. By contrast, a streamlined, 'shrinking-like' foil avoids generating the ring vortex, leaving a structurally simpler wake. The 'shrinking' foil also recovers a large part of the initial energy from the fluid, resulting in much weaker wake structures. Finally, a sharp-edged but hollow, 'melting-like' foil provides an energetic wake while avoiding the generation of a vortex ring. As a result, a melting-like body forms a simple and highly energetic and stable wake, that entrains all of the original added mass fluid energy. The three conditions studied correspond to different modes of flow control employed by aquatic animals and birds, and encountered in disappearing bodies, such as rising bubbles undergoing phase change to fluid.

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Boundary data immersion method for Cartesian-grid simulations of fluid-body interaction problems

Cited by 116 publications

References 26 publications

Unsteady dynamics of rapid perching manoeuvres

Unsteady dynamics of rapid perching manoeuvres

Performance augmentation mechanism of in-line tandem flapping foils

Shape of retracting foils that model morphing bodies controls shed energy and wake structure

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