Theory for Aerodynamic Force and Moment in Viscous Flows

Wu, J. C.

doi:10.2514/3.50966

Cited by 344 publications

(224 citation statements)

References 11 publications

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“…Collectively, the last two terms in equation (1) account for the total 'bound circulation' of the bodies (the net cyclic constant associated with tight counter-clockwise loops around the bodies) in an inviscid problem. The force exerted by the fluid on a body (or set of bodies) in viscous or inviscid flow can be written in terms of rates of change of linear impulse [13,14],…”

Section: Methodsmentioning

confidence: 99%

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A Reconciliation of Viscous and Inviscid Approaches to Computing Locomotion of Deforming Bodies

Eldredge

2009

Exp Mech

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We present a formulation for coupled solutions of fluid and body dynamics in problems of biolocomotion. This formulation unifies the treatment at moderate to high Reynolds number with the corresponding inviscid problem. By a viscous splitting of the Navier-Stokes equations, inertial forces from the fluid are distinguished from the viscous forces, and the former are further decomposed into contributions from body motion in irrotational fluid and ambient fluid vorticity about an equivalent stationary body. In particular, the added mass of the fluid is combined with the intrinsic inertia of the body to allow for simulations of bodies of arbitrary mass, including massless or neutrally buoyant bodies. The resulting dynamical equations can potentially illuminate the role of vorticity in locomotion, and the fundamental differences of locomotion in real and perfect fluids.

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Section: Methodsmentioning

confidence: 99%

“…Regardless of whether the flow is inviscid or viscous, the total vorticity of the global system of bodies and fluid is constrained by Kelvin's circulation theorem [13],…”

Section: Methodsmentioning

confidence: 99%

A Reconciliation of Viscous and Inviscid Approaches to Computing Locomotion of Deforming Bodies

Eldredge

2009

Exp Mech

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“…3, the relationship between aerodynamic force and vorticity fields can be derived by adopting the vorticity-moment theorem developed by Wu (1981Wu ( , 2005. The aerodynamic force acting on a solid body is given by…”

Section: Resultsmentioning

confidence: 99%

An experimental study of the effects of pitch-pivot-point location on the propulsion performance of a pitching airfoil

Tian

Bodling

Liu

et al. 2016

Journal of Fluids and Structures

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a b s t r a c tAn experimental investigation was conducted to characterize the evolution of the unsteady vortex structures in the wake of a pitching airfoil with the pitch-pivot-point moving from 0.16C to 0.52C (C is the chord length of the airfoil). The experimental study was conducted in a low-speed wind tunnel with a symmetric NACA0012 airfoil model in pitching motion under different pitching kinematics (i.e., reduced frequency k ¼3.8-13.2). A high-resolution particle image velocimetry (PIV) system was used to conduct detailed flow field measurements to quantify the characteristics of the wake flow and the resultant propulsion performance of the pitching airfoil. Besides conducting "free-run" PIV measurements to determine the ensemble-averaged velocity distributions in the wake flow, "phase-locked" PIV measurements were also performed to elucidate further details about the behavior of the unsteady vortex structures. Both the vorticity-moment theorem and the integral momentum theorem were used to evaluate the effects

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“…, and V ∞ is an infinite fluid domain at rest at infinity (Wu 1981). Therefore, the dimensional impulse acting on the plate (= ∞ 0…”

Section: Resultsmentioning

confidence: 99%

Vortex dynamics of clapping plates

2013

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Vortex formation and force generation of clapping plates with various aspect ratios (AR) and stroke angles were investigated. Experiments were performed with a pair of hinged rectangular plates that were rotated symmetrically in a static fluid, and defocusing digital particle image velocimetry was employed to measure the threedimensional flow field. Single-plate cases were also studied to compare with clapping plate cases. As AR decreases, both circulation of the tip vortex and area enclosed by the vortex loop increase inversely. An empirical power-law relationship with a negative exponent is found between total impulse and AR for a given stroke angle. The sensitivity of the force generated by the plates to the change of AR is larger at the smaller stroke angle because of faster acceleration and deceleration. The increase in impulse per plate from the single-plate case to the clapping double-plate case is larger for lower AR. These results reveal that low AR wings are more efficient in propulsive force generation in some specific modes of unsteady flapping flight. The evolution of the wake structures is found to depend on AR and stroke angle.

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Theory for Aerodynamic Force and Moment in Viscous Flows

Cited by 344 publications

References 11 publications

A Reconciliation of Viscous and Inviscid Approaches to Computing Locomotion of Deforming Bodies

A Reconciliation of Viscous and Inviscid Approaches to Computing Locomotion of Deforming Bodies

An experimental study of the effects of pitch-pivot-point location on the propulsion performance of a pitching airfoil

Vortex dynamics of clapping plates

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