Unsteady aerodynamics of porous aerofoils

Baddoo, Peter J.; Hajian, Rozhin; Jaworski, Justin

doi:10.1017/jfm.2020.1031

Cited by 10 publications

(8 citation statements)

References 79 publications

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“…In a similar investigation of circular perforated plates, Steiros et al (2020) also showed how variable distributions of holes may strongly modify the flow morphology and the resulting aerodynamic forces. Other analytical investigations of the aerodynamic forces on porous airfoils have been performed by Hajian & Jaworski (2017) and Baddoo, Hajian & Jaworski (2021). In Hajian & Jaworski (2017) a potential flow model to evaluate the aerodynamic forces on thin permeable airfoils was proposed.…”

Section: Introductionmentioning

confidence: 99%

“…The presence of a porous structure was described by a seepage flow rate through the permeable surface. Baddoo et al (2021) generalized this analysis to the unsteady case such as pitching and heaving motion or gust loads. Other experimental investigations focused on the drag variation of porous disks at low Reynolds numbers (Strong et al 2019) and on the fluid-structure interaction of porous flexible strips (Pezzulla et al 2020), to name a few.…”

Section: Introductionmentioning

confidence: 99%

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Homogenization-based design of microstructured membranes: wake flows past permeable shells

et al. 2021

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A formal framework to characterize and control/optimize the flow past permeable membranes by means of a homogenization approach is proposed and applied to the wake flow past a permeable cylindrical shell. From a macroscopic viewpoint, a Navier-like effective stress jump condition is employed to model the presence of the membrane, in which the normal and tangential velocities at the membrane are respectively proportional to the so-called filtrability and slip numbers multiplied by the stresses. Regarding the particular geometry considered here, a characterization of the steady flow for several combinations of constant filtrability and slip numbers shows that the flow morphology is dominantly influenced by the filtrability and exhibits a recirculation region that moves downstream of the body and eventually disappears as this number increases. A linear stability analysis further shows the suppression of vortex shedding as long as large values of the filtrability number are employed. In the control/optimization phase, specific objectives for the macroscopic flow are formulated by adjoint methods. A homogenization-based inverse procedure is proposed to obtain the optimal constrained microscopic geometry from macroscopic objectives, which accounts for fast variations of the filtrability and slip profiles along the membrane. As a test case for the proposed design methodology, a cylindrical membrane is designed to maximize the resulting drag coefficient.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Homogenization-based design of microstructured membranes: wake flows past permeable shells

et al. 2021

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“…At the same time, its numerical solution (e.g. Baddoo, Hajian & Jaworski 2021) renders the slender body approximation redundant. There is hardly any benefit in attempting a numerical solution of an approximate model in the framework of the potential flow theory, when a fast numerical solution of the exact model in the framework of the same theory is readily available (Appendix H).…”

Section: The Aft Segmentmentioning

confidence: 99%

A unified theory of slender wings in asymmetric motion, with an application to a swimming sea snake

Iosilevskii

2022

J. Fluid Mech.

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The slender body theory is extended to accommodate cases where a wing, in generally non-uniform motion, sideslips at sufficiently large angle to make the flow separate from one of its long edges but not from any part of the other. In those cases, an approximately triangular wake forms to the side of the wing, rendering the pressure loads on the wing not only asymmetrical, but also dependent on the history of the wing's motion. The theory can have a wide range of possible applications, from estimating lift and drag of a slender wing in pronouncedly asymmetric flight, through analysing an aero-elastic stability of that wing, to estimating thrust, lift and power of a sea snake that swims at an angle to its body axis. Coherence of the theory is demonstrated through numerous numerical simulations.

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“…(2020) among others. Nevertheless, almost all unsteady models, starting with the pioneering efforts in the 1920s and 1930s of Wagner (1925), Theodorsen (1935) and Von Kármán & Sears (1938) until the recent work of Baddoo, Hajian & Jaworski (2021), adopted the Kutta condition. There is no legitimate alternative!…”

Section: Introduction: Meager State Of Theoretical Modelling Of Aerod...mentioning

confidence: 99%

“…This is why numerous research reports have criticized the application of the Kutta condition to unsteady flows (Woolston & Castile 1951;Rott & George 1955;Chu 1961;Henry 1961;Shen & Crimi 1965;Abramson, Chu & Irick 1967;Orszag & Crow 1970;Basu & Hancock 1978;Daniels 1978;Satyanarayana & Davis 1978;Savage, Newman & Wong 1979;Bass, Johnson & Unruh 1982;Crighton 1985), including the recent efforts of Xia & Mohseni (2017), Taha & Rezaei (2019) and Zhu et al (2020) among others. Nevertheless, almost all unsteady models, starting with the pioneering efforts in the 1920s and 1930s of Wagner (1925), Theodorsen (1935) and Von Kármán & Sears (1938) until the recent work of Baddoo, Hajian & Jaworski (2021), adopted the Kutta condition. There is no legitimate alternative!…”

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confidence: 99%

A variational theory of lift

Gonzalez

Taha

2022

J. Fluid Mech.

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In this paper we revive a special, less-common, variational principle in analytical mechanics (Hertz’ principle of least curvature) to develop a novel variational analogue of Euler's equations for the dynamics of an ideal fluid. The new variational formulation is fundamentally different from those formulations based on Hamilton's principle of least action. Using this new variational formulation, we generalize the century-old problem of the flow over a two-dimensional body; we developed a variational closure condition that is, unlike the Kutta condition, derived from first principles. The developed variational principle reduces to the classical Kutta–Zhukovsky condition in the special case of a sharp-edged airfoil, which challenges the accepted wisdom about the Kutta condition being a manifestation of viscous effects. Rather, we found that it represents conservation of momentum. Moreover, the developed variational principle provides, for the first time, a theoretical model for lift over smooth shapes without sharp edges where the Kutta condition is not applicable. We discuss how this fundamental divergence from current theory can explain discrepancies in computational studies and experiments with superfluids.

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Unsteady aerodynamics of porous aerofoils

Abstract: Abstract

Cited by 10 publications

References 79 publications

Homogenization-based design of microstructured membranes: wake flows past permeable shells

Homogenization-based design of microstructured membranes: wake flows past permeable shells

A unified theory of slender wings in asymmetric motion, with an application to a swimming sea snake

A variational theory of lift

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