A concept is presented for the development and implementation of a prototype Aircraft Vortex Spacing System (AVOSS). The purpose of the AVOSS is to use current and short-term predictions of the atmospheric state in approach and departure corridors to provide, to ATC facilities, dynamical weather dependent separation criteria with adequate stability and lead time for use in establishing arrival ...

Past study of interspecific variation in the swimming speed of fishes has focused on internal physiological mechanisms that may limit the ability of locomotor muscle to generate power. In this paper, we approach the question of why some fishes are able to swim faster than others from a hydrodynamic perspective, using the technique of digital particle image velocimetry which allows measurement o...

Numerical simulations are used to investigate the effect of aspect ratio on the wake topology and hydrodynamic performance of thin ellipsoidal flapping foils. The study is motivated by the quest to understand the hydrodynamics of fish pectoral fins. The simulations employ an immersed boundary method that allows us to simulate flows with complex moving boundaries on fixed Cartesian grids. A deta...

A generalized variational equation based on the extended Hamilton’s principle is presented as the starting point for a procedure from which wake-body models for the two-dimensional vortex-induced vibration of a cylinder can be derived. The case of an elastically mounted cylinder with a transverse degree-of-freedom in a uniform flow is offered as a ‘‘model problem’’ through which this derivation...

The vortical structures in the rear separation and wake region produced by a micro-ramp that immersed in a supersonic turbulent boundary layer are investigated. The small scale separation was reveled close to the trailing edge and confirms the previous experimental observation. Between the reverse region and surrounding fast moving flow, a three-dimensional shear layer was formed, where vortice...

Stratified flow past a three-dimensional obstacle such as a sphere has been a long-lasting subject of geophysical, environmental and engineering fluid dynamics. In order to investigate the effect of the stratification on the near wake, in particular, the unsteady vortex formation behind a sphere, numerical simulations of stratified flows past a sphere are conducted. The time-dependent NavierSto...

We present dye visualizations of the wake behind a flexible plate flow when its leading edge is forced into harmonic heave motion. We show that, when the forcing amplitude is sufficiently large, a reverse Bénard-von Kármán vortex street is formed in the wake, indicative of the production of positive thrust.

A flexibly mounted circular cylinder in cross-flow, with natural frequencies in the inline and transverse directions having a ratio close to 2:1, exhibits drastic changes in the vortex structures in its wake, the frequency content of the fluid forces, and the orbital shape of its resulting motions. Stable multivortex patterns form in the cylinder wake, associated with large high-frequency force...

Simultaneous swimming kinematics and hydrodynamics are presented for American eels, Anguilla rostrata, swimming at speeds from 0.5 to 2 L s(-1). Body outlines and particle image velocimetry (PIV) data were collected using two synchronized high-speed cameras, and an empirical relationship between swimming motions and fluid flow is described. Lateral impulse in the wake is estimated assuming that...