Bulletin of the American Physical Society
73rd Annual Meeting of the APS Division of Fluid Dynamics
Volume 65, Number 13
Sunday–Tuesday, November 22–24, 2020; Virtual, CT (Chicago time)
Session W03: Aerodynamics: Theory (10:00am - 10:45am CST)Interactive On Demand
|
Hide Abstracts |
|
W03.00001: Nonlinear models for the indicial force response on an airfoil in unsteady conditions Scott Dawson, Steven Brunton This work presents a methodology for modeling the transient response in lift on an airfoil subject to a sudden change in conditions, for both idealized and more realistic flows. For idealized flows, from classical unsteady aerodynamic theory the response of an airfoil’s lift subject to a change in angle of attack or freestream velocity is encapsulated by the Wagner function. While this function is well known, an explicit expression is difficult to obtain, as its formulation requires the computation of an inverse Laplace transform (or similar inversion) of a non-rational function. This has led to numerous proposed approximations to the Wagner function (or equivalently, to the Theodorsen function), which facilitate convenient and rapid computation. While these approximations are sufficient for many applications, common linear approximations do not capture the correct asymptotic behavior over large time horizons. We show that the Wagner function is more naturally approximated by the response of a nonlinear scalar ordinary differential equation, which can be identified through sparsity-promoting identification methods. We also show that this methodology can be applied to model the lift response for more realistic aerodynamic flows, incorporating nonplanar wakes and viscous effects. [Preview Abstract] |
|
W03.00002: Abstract Withdrawn
|
|
W03.00003: The effect of Viscous Boundary Condition On Kelvin's Conservation of Circulation: Modified Theodorsen Function Amir S. Rezaei, Haithem Taha One of the essential tools that have been ubiquitously used in theoretical modeling of unsteady aerodynamics is Kelvin's law of zero total circulation. It implies that, for inviscid fluids, the total circulation in the fluid domain is conserved yielding a relation between the bound and wake circulation. In this study, we show that, by virtue of the viscous boundary condition (no slip), the vorticity generated on the fluid-solid interface (which is proportional to the angular velocity of the body) disturbs such a conservation law. Taking this viscous contribution into account, we developed an extension of Theodorsen's inviscid lift frequency response in the case of a pitching airfoil. The results show more phase lag and lift deficiency compared to Thodorsen's function, which have been reported by many scholars in the literature, and also validated against URANS simulations in this study. [Preview Abstract] |
|
W03.00004: Investigation of Lift Distribution and Its Effect on Aerodynamic Performance Scott Weekley, Cole Kelly, Jamey Jacob This effort evaluates the use of bell-shape lift distributions, as opposed to elliptical, to improve aerodynamic performance of flying-wing aircraft configurations. Such a distribution was originally proposed by Prandtl in 1923 to minimize bending moment along the wing and thus reduce structural wing weight. Using unique, geometric wing twist to change the lift distribution, the landscape of regions of upwash and downwash change with potential ramifications for drag reduction. Through a computational fluid dynamics (CFD) investigation, we evaluate how these changes impact aerodynamic efficiency. In particular, the efficacy of a coordinated turn is examined by observing how the inboard regions of upwash create induced thrust at the aileron-deflected wingtips. This induced thrust creates a favorable differential longitudinal force in roll, otherwise known as proverse yaw. CFD results indicate that the use of a bell-shaped lift distribution may improve aerodynamic performance for certain aircraft configurations. [Preview Abstract] |
|
W03.00005: Geometry-agnostic Methods for Determining Bound Circulation in Potential Flows Cody Gonzalez, Haithem Taha A core detriment of potential flow theory, inherent in its kinematic nature, is that it is agnostic of the local work required to produce its divergence-free flowfield. The auxiliary Kutta-Joukowski condition has long served in prescribing circulation for airfoils at low angles of attack, but leads to unsatisfactory predictions for unsteady, separated flows, and its lack of a mathematical basis has made its extensions to these nonlinear regimes ad hoc and geometry dependent. This research posits existence of an upper bound on acceleration within the flowfield, and moreover, that such a limit is a function of streamtube diameter, Reynolds number, and Mach number, representing the constraints, ratio of inertial and viscous forces, and the ratio of local flow velocity to the speed of sound, respectively. Novel, geometry-agnostic methods, using the variational concepts of least constraint, and minimization of maximum accelerations, are presented for determination of bound circulation; both of which require no a priori assumptions for circulation or separation points. The result serves as a physical basis for obviating the Kutta-Joukowski condition, in a form which is amenable to aerodynamic analysis of arbitrary geometry in nonlinear and unsteady regimes. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700