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.

When a cylindrical tool cuts through a thin sheet of a relatively brittle material, it leaves behind a visually arresting crack street in its wake, reminiscent of a vortex street in the wake of a cylinder moving through a fluid. We show that simple geometrical arguments based on the interplay of in-plane stretching and out-of-plane bending suffice to explain the cycloidal morphology of the curv...

Abstract The thrust producing performance and efficiency of an SD8020 oscillating foil with a symmetrical saw-tooth angle of attack pitching profile was studied through force and torque measurements, as well as dye flow visualization, in the water tunnel at low Reynolds number of 13,000-16,000. The propulsive efficiency and thrust coefficient of the pitching foil were determined as a function o...

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...

The wake in the flow past a circular cylinder has posed a long-standing challenge to scientists since the late 19th century. Many aspects of this seemingly simple phenomenon remain unexplained. Of particular interest is the relationship between the dimensionless vortex shedding frequency (the Strouhal number St) and the ratio of inertial to viscous forces in the fluid (the Reynolds number Re). ...

The fluid-structure interaction of flexible bodies in steady and unsteady flow is a key area of interest for the development of underwater vehicles. In the design of marine vehicles the flow can often be seen as an obstacle to overcome, whilst in nature a fish interacts with the flow and is capable of achieving a high level of efficiency. Therefore by understanding how fish – or flexible bodies...

Flow and flow-induced vibration of a square array of cylinders are investigated by two-dimensional numerical simulations. Flow past 36 cylinders in an inline arranged square array and 33 cylinders in a staggered arranged square array is firstly simulated, for Re=100 and the spacing ratios of L/D=1.5, 2, 3, 4, 5. Only one vortex street is observed in the wake of the cylinder array when the spaci...