A simple experiment demonstrates that an average vertical force can be produced by a small vibrator motor attached to a frame constrained to slide vertically on guide wires. The vertical force produced is sufficient to make the sliding element hover, similarly to a biologically inspired robotic insect. We show that this effect depends on the natural resonance frequency of the guide wires and the nature of the mechanical coupling between wires and sliding element. Based on the result of this experiment, we recommend that a control experiment should be performed in order to reach unambiguous conclusions concerning the actual flying capabilities of robotic insects tested using this kind of methodology.

This paper presents a computational framework to extract salient patterns, called vortex structures, from 3D turbulent fluid flows. These structures can be characterized as regions of dominating rotational motion in the velocity fields and intensity concentrations in the corresponding vorticity fields. A pointwise linear representation is employed to approximate the kinematics of the flow field, and the fluid motion is classified according to motion analysis or topological patterns. The regions of vortex structures are identified as those dominated by rotational motion or those of focus-type singularity. The 2D vortices, as a special case of 3D vortices, are detected by searching for regions of vorticity concentrations.

A new approach of image processing is proposed to enhance the spatial resolution of fluid flow field measurement. The local estimate velocity is first found in a sub-image region. The particles in the region are then located individually. The corresponding particles are matched by using the estimate velocity and the particle locations in conjunction, making it possible to produce mole velocity measurements from the smallest particle image velocimetry (PIV) measurement sub-region. The proposed method has been proved successful by testing the experimental result from Urushihara et al. (1986).

This paper presents a framework for analyzing salient patterns (vortex structures) in the velocity fields of turbulent fluid flows. Vortices are modeled as rotational motions in the velocity fields and concentrations in the corresponding vorticity fields. A pointwise linear model is then built to approximate the kinematics of the flow field. Locally, the vector fields are analyzed in terms of fluid motion and singular patterns. The regions of vortex structures are then extracted by identifying those dominated by rotational motion or those of focus-type singularity. In addition to this, 2D vortices, as a special case, are detected by searching regions of vorticity concentrations. The algorithm is applied to both 2D and 3D, experimental and computational turbulent flows.>