A low-order point vortex model for the two-dimensional unsteady aerodynamics of a flat plate wing section is developed. A vortex is released from both the trailing and leading edges of the flat plate, and the strength of each is determined by enforcing the Kutta condition at the edges. The strength of a vortex is frozen when it reaches an extremum, and a new vortex is released from the corresponding edge. The motion of variable-strength vortices is computed in one of two ways. In the first approach, the Brown–Michael equation is used in order to ensure that no spurious force is generated by the branch cut associated with each vortex. In the second approach, we propose a new evolution equation for a vortex by equating the rate of change of its impulse with that of an equivalent surrogate vortex with identical properties but constant strength. This impulse matching approach leads to a model that admits more general criteria for shedding, since the variable-strength vortex can be exchanged for its constant-strength surrogate at any instant. We show that the results of the new model, when applied to a pitching or perching plate, agree better with experiments and high-fidelity simulations than the Brown–Michael model, using fewer than ten degrees of freedom. We also assess the model performance on the impulsive start of a flat plate at various angles of attack. Current limitations of the model and extensions to more general unsteady aerodynamic problems are discussed.
Related Content
Periodically plunging foil near a free surface
Experiments were performed to investigate the effects of amplitude and depth on the drag reduction of a NACA 0012 airfoil plunging near a free surface for a range of frequencies. Beyond the effect of the free surface, at low Strouhal numbers based on amplitude, SrA, the drag reduction follows a p...


Tethered cube stabilization by means of leading-edge DBD plasma actuation
An experimental investigation was carried out to assess the effectiveness of active flow control as a means for suppressing oscillations of a tethered cube. Two experimental configurations were considered: a static configuration involving surface pressure and particle image velocimetry (PIV) flow...
Finite-span rotating wings: three-dimensional vortex formation and variations with aspect ratio
We investigate experimentally the effect of aspect ratio ( > ) on the time-varying, three-dimensional flow structure of flat-plate wings rotating from rest at 45° angle of attack. Plates of > = 2 and 4 are tested in a 50 % by mass glycerin–water mixture, with a total rotation of ϕ = 120° ...


Nonsinusoidal motion effects on energy extraction performance of a flapping foil
To seek better energy extraction performance of a flapping hydrofoil, various nonsinusoidal motion profiles are employed instead of conventional sinusoidal flapping motions. The effects of nonsinusoidal motions are investigated for four kinds of nonsinusoidal flapping motions, i.e. varying effect...
Formation of vortex breakdown in conical–cylindrical cavities
Numerical simulations in confined rotating flows were performed in this work, in order to verify and characterize the formation of the vortex breakdown phenomenon. Cylindrical and conical–cylindrical geometries, both closed, were used in the simulations. The rotating flow is induced by the bott...

Ground effect on the aerodynamics of a two-dimensional oscillating airfoil
This paper reports results of an experimental investigation into ground effect on the aerodynamics of a two-dimensional elliptic airfoil undergoing simple harmonic translation and rotational motion. Ground clearance (D) ranging from 1c to 5c (where c is the airfoil chord length) was investigated ...
Role of β-Hairpin Formation in Aggregation: The Self-Assembly of the Amyloid-β(25–35) Peptide
The amyloid-β(25–35) peptide plays a key role in the etiology of Alzheimer's disease due to its extreme toxicity even in the absence of aging. Because of its high tendency to aggregate and its low solubility in water, the structure of this peptide is still unknown. In this work, we sought to u...

An overview on heat transfer augmentation using vortex generators and nanofluids: Approaches and applications
The subject of heat transfer enhancement has significant interest to develop the compact heat exchangers in order to obtain a high efficiency, low cost, light weight, and size as small as possible. Therefore, energy cost and environmental considerations are going on to encourage attempts to inven...
On the competition between leading-edge and tip-vortex growth for a pitching plate
The interaction between leading-edge-vortex and tip-vortex development on a low-aspect-ratio plate has been investigated and compared to a nominally two-dimensional rectangular flat plate. Simultaneous to force measurements, three-dimensional particle tracking velocimetry (3D-PTV) was used to cha...

Berezinskii-Kosterlitz-Thouless transition in a photonic lattice
Phase transitions give crucial insight into many-body systems, as crossoversbetween different regimes of order are determined by the underlying dynamics. These dynamics, in turn, are often constrained by dimensionality and geometry. For example, in one- and two-dimensional systems with continuous...