A special arrangement of spinning strings with dislocations similar to a von Kármán vortex street is studied. We numerically solve the geodesic equations for the special case of a test particle moving along two infinite rows of pure dislocations and also discuss the case of pure spinning defects. PACS numbers: 04.20 Jb, 04.50.+h, 11.10.Lm, 47.32.Cc Conical singularities or spacetime defects are...

Motivation. Understanding vector fields is integral to many scientific applications ranging from combustion to global oceanic eddy simulations. Critical points of a vector field (zeros of the field) are essential features of the data, and play an important role in describing and interpreting the flow behavior. However, vector field analysis based on critical points suffers a major drawback: the...

Despite the large amount of research devoted to bluff body wakes [1], very few studies have focused on stratified wakes despite their obvious applications to geophysical flows. Moreover, most of these studies have studied the turbulent regime in the wake of a sphere or an ellipsoid [2,3], due to its naval applications for submarine wakes. These bluff bodies have a finite height, which leads to ...

A variant of a gauge theory is formulated to describe disclinations on Riemannian surfaces that may change both the Gaussian (intrinsic) and mean (extrinsic) curvatures, which implies that both internal strains and a location of the surface in R 3 may vary. Besides, originally distributed disclinations are taken into account. For the flat surface, an extended variant of the Edelen-Kadi´c gauge ...

The synthesis of a comprehensive theory of force production in insect flight is hindered in part by the lack of precise knowledge of unsteady forces produced by wings. Data are especially sparse in the intermediate Reynolds number regime (10<Re<1000) appropriate for the flight of small insects. This paper attempts to fill this deficit by quantifying the time-dependence of aerodynamic forces for...

We study experimentally the vortex streets produced by a flapping foil in a hydrodynamic tunnel, using two-dimensional particle image velocimetry. An analysis in terms of a flapping frequency-amplitude phase space allows the identification of (i) the transition from the well-known Bénard-von Kármán (BvK) wake to the reverse BvK vortex street that characterizes propulsive wakes, and (ii) the sym...

We consider streamline patterns associated with single and double von Kármán point vortex streets on the surface of a nonrotating sphere, with and without pole vortices. The full family of streamline patterns are identified and the topological bifurcations from one pattern to another are depicted as a function of latitude and pole strength. The process involves first finding appropriate vortex ...

We report on the experimental observation of vortex cluster shedding from a moving obstacle in an oblate atomic Bose-Einstein condensate. At low obstacle velocities v above a critical value, vortex clusters consisting of two like-sign vortices are generated to form a regular configuration like a von Kármán street, and as v is increased, the shedding pattern becomes irregular with many different...

In 1911 Theodore von Kármán first noticed the unusual alternating stream of vortices that result from fluid flowing past a cylinder. This phenomenon, now known as a von Kármán vortex street, only occurs for fluids with particular characteristics. The most important attribute, is the Reynolds number, which is the ratio of inertial forces to viscous forces in the fluid. It turns out that vortices...

We present an effective technique for suppressing the vortex-induced vibrations of bluff bodies by eliminating the von Kármán street formed in their wake. Specifically, we find that small amounts of combined windward suction and leeward blowing around the body modify the wake instability and lead to suppression of the fluctuating lift force. Three-dimensional simulations and stability analysis ...