Applications of modern hydrodynamics to aeronautics

Tollmien, Walter; Schlichting, Hermann; Görtler, Henry; Riegels, Friedrich W.

doi:10.1007/978-3-662-11836-8_32

Cited by 9 publications

(17 citation statements)

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“…This results in no vertical momentum in or out (the dashed line has returned to the horizontal centreline). Instead, all the force is the over pressure at the earth's surface, as shown by (Prandtl 1921). This second example is analogous to the method used to measure lift for NACA aerofoils by NASA (Von Doenhoff and Abbott 1947).…”

Section: Discussionmentioning

confidence: 99%

“…Mclean (2012) explains that while even though the local vertical velocity tends to zero, there is a distribution of the vertical velocity components. Importantly, the end result of the momentum transfer is to transmit the force from the wing to the earth's surface (Prandtl 1921, Mclean 2012). It should be noted there are those that incorrectly believe this is not the case (Anderson and Eberhardt 2009).…”

Section: Discussionmentioning

confidence: 99%

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Is that lift diagram correct? A visual study of flight education literature

Wild

2023

Phys. Educ.

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With a complex topic such as aerodynamics, subtle points are critical. In this work images illustrating air flow around wings and aerofoils were studied to explore misunderstandings in aerodynamics education. While these images are common in textbooks and popular science media, this study was limited to the 135 physics education articles on the topic of lift, of which 49 contained illustrations of air flow around an aerofoil or wing. These 49 cases were included for qualitative comparison using visual semiotics. It was found that 28% of images did not include upwash, and only 44% included stagnation points. For the case of 2D flow around aerofoils 30% were illustrated correctly, while for wings 75% were correct. These results excluded the seven completely incorrect illustrations where common misconceptions were presented as facts. Most illustrations of flow around an aerofoil incorrectly depicted flow around a wing.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Is that lift diagram correct? A visual study of flight education literature

Wild

2023

Phys. Educ.

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“…For generation at a sharp edge of the body, where an inviscid formulation allows for the Kutta condition (Crighton 1985) to be imposed, the vortex dynamics are independent of the body's length scale. This has motivated self-similar solutions that have been widely reported in the literature (Prandtl 1921;Kaden 1931;Alexander 1971;Pullin 1978). These calculations have generally focused on (i) vortex sheet formulations, in which the fluid velocity is discontinuous across the sheet, and (ii) point vortex approaches that localise the generated vorticity at singular points in space (Cortelezzi & Leonard 1993;Krasny & Nitsche 2002;Jones 2003;Tchieu & Leonard 2011).…”

Section: Introductionmentioning

confidence: 91%

“…This vortex generation often provides a dominant contribution to the lift experienced by the body and, hence, its † Email address for correspondence: jsader@caltech.edu characterisation is essential in practice. The physical processes underlying this generation have been the subject of intensive research over the past century due to their importance in aerodynamics (Prandtl 1921;Graham 1983;Pullin & Wang 2004;Jones & Babinsky 2010). The form of the starting vortex and its sensitivity to its surrounding (irrotational) flow field are also used in nature, e.g.…”

Section: Introductionmentioning

confidence: 99%

Starting vortices generated by an arbitrary solid body with any number of edges

Hinton,

Leonard,

Pullin

et al. 2024

J. Fluid Mech.

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The starting vortex generated at the trailing edge of a flat plate, that is impulsively translated at fixed angle of attack, is a widely studied canonical problem. Recent work that examined the effect of plate rotation on this starting vortex found that two new and distinct vortex sheet types can arise. We generalise this work to study the starting vortex generated at any sharp and straight edge of an arbitrary body under a general time-dependent two-dimensional motion. The dimensionless velocity field of the attached flow near any sharp edge is assumed to take the form, $\hat {z}^{-1/2} f(T) + g(T) + o (1)$ , where $\hat {z}$ is the dimensionless position referenced to the edge, $f(T)$ and $g(T)$ are functions of dimensionless time, $T$ , associated with the local flow perpendicular and parallel to the edge, respectively. This enables starting vortices to be generally calculated and their types related by simply inspecting the forms of $f(T)$ and $g(T)$ . We elucidate the physics underlying all three vortex types and show that these vortices are generated by pure translation of the sharp edge. Several case studies are explored, including the leading/trailing edge vortices of a flat plate which can simultaneously be of different type (relevant to low-speed aircraft), the vortex formed by translation of a semi-infinite flat plate and the trailing-edge vortex of Joukowski aerofoils. With the ability to calculate the vortices at all edges, the theory is used to develop a general formula for the lift force of a flat plate which can find application in practice.

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“…We consider cases of both straight and swept wings. For the straight wing, the three models are compared against predictions from classical lifting line theory [40] as it provides the most convenient analytical solution for such wing geometry (no sweep and the aspect ratio is above three [41][42][43][44]). For the swept wing case, the models were compared against available experimental data from a 45 degree swept wing of aspect ratio 5 [45].…”

Section: Appendix a Model Selectionmentioning

confidence: 99%

A Novel Control Allocation Method for Yaw Control of Tailless Aircraft

et al. 2020

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Tailless aircraft without vertical stabilisers typically use drag effectors in the form of spoilers or split flaps to generate control moments in yaw. This paper introduces a novel control allocation method by which full three-axis control authority can be achieved by the use of conventional lift effectors only, which reduces system complexity and control deflection required to achieve a given yawing moment. The proposed method is based on synthesis of control allocation modes that generate asymmetric profile and lift induced drag whilst maintaining the lift, pitching moment and rolling moment at the trim state. The method uses low order models for aerodynamic behaviour characterisation based on thin aerofoil theory, lifting surface methodology and ESDU datasheets and is applied to trapezoidal wings of varying sweep and taper. Control allocation modes are derived using the zero-sets of surrogate models for the characterised aerodynamic behaviours. Results are presented in the form of control allocations for a range of trimmed sideslip angles up to 10 degrees optimised for either maximum aerodynamic efficiency (minimum drag for a specific yawing moment) or minimum aggregate control deflection (as a surrogate observability metric). Outcomes for the two optimisation objectives are correlated in that minimum deflection solutions are always consistent with efficient ones. A configuration with conventional drag effector is used as a reference baseline. It is shown that, through appropriate allocation of lift based control effectors, a given yawing moment can be produced with up to a factor of eight less aggregate control deflection and up to 30% less overall drag compared to use of a conventional drag effector.

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Applications of modern hydrodynamics to aeronautics

Cited by 9 publications

References 0 publications

Is that lift diagram correct? A visual study of flight education literature

Is that lift diagram correct? A visual study of flight education literature

Starting vortices generated by an arbitrary solid body with any number of edges

A Novel Control Allocation Method for Yaw Control of Tailless Aircraft

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