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This picture shows the top view of the wake behind a ãvirtualä insect flying in fluid. The model of the insect is translated in water horizontally. It has a permanent magnet in its rear end which provides a magnetic field in the direction of motion. At the same time the electric current flows between two electrodes in a perpendicular direction in the horizontal plane. The resulting Lorentz force on the fluid is perpendicular to both the current and the magnetic field and acts in the vertical direction. This force, if applied impulsively during some time intervals, simulates the lift force applied by the flapping wings of an insect during
down strokes. This force transfers momentum downwards while the reaction to this force supports the insect in the air. Momentum transfers in the form of vortex rings. These ãringsä look like a Greek letter Omega and are connected to each other. The insect is small and the viscosity of the fluid is important. As a result the vortex tubes diffuse in the fluid.
Contributor: Y. D. Afanasyev, Memorial University of Newfoundland, St. John's, Canada
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