Shedding of vortices is a common phenomenon in the atmosphere over a wide range of spatial and temporal scales. However, it is unclear how these vortices of varying scales affect the flight performance of flying animals. In order to examine these interactions, we trained seven hawkmoths (Manduca sexta) (wingspan ~9 cm) to fly and feed in a wind tunnel under steady flow (controls) and in the von...

The combustion of a freely falling dodecane droplet has been studied experimentally in droptower-like facility under ambient conditions. A unique ignition mechanism is used by igniting the pendant mode and releasing it to fall freely. This unveils different type wake flame behavior which explored this study. Initially, transitions from fully enveloped configuration due forward extinction. simil...

1 Lagrangian analysis is capable of revealing the underlying structure and complex phenomena in unsteady flows. We present Particle-Image Velocimetry measurements of the wake of a cylinder undergoing streamwise vortex-induced vibrations and calculate the Finite-Time Lyapunov Exponents (FTLE) in backward-and forward-time. The FTLE fields are compared to the phase-averaged vorticity fields for th...

Using the geometrical optics approximation, a theoretical prediction of the deflection angle correlation of a laser beam propagating in a hot turbulent jet is found as a functional form of the turbulent spectrum of the refractive index fluctuations. By applying the modified Von Karman model and Tatarskii model, the structure coefficient of the refractive index and the deflection angle correlati...

We simulate turbulence in a plane Couette geometry by a spectral method intermediate between full resolution and the complete elimination of small modes common in large eddy simulations. The wave number grid is sparse in spanwise and downstream direction, with a total number of modes proportional to Re(3/4) lnRe. At a Reynolds number of 2000 we could suppress more than 80% of the modes and stil...

We discuss the stability of icosadeltahedral shells subjected to a uniform external load in the form of an isotropic pressure. We demonstrate that there exists a universal critical buckling pressure scaling form that defines a locus of buckling instabilities. The parameter that uniquely determines this scaling form is shown to be the Föppl-von Karman number of nonpressurized shells. Numerical r...

This paper develops a model for evolving wrinkles in a bilayer thin film consisting of an elastic layer and a viscoelastic layer. The elastic layer is subjected to a compressive residual stress and is modeled by the nonlinear von Karman plate theory. A thin-layer approximation is developed for the viscoelastic layer. The stability of the bilayer and the evolution of wrinkles are studied first b...

An angular spectrum representation is applied for a description of statistical properties of arbitrary beamlike fields propagating through atmospheric turbulence. The Rytov theory is used for the characterization of the perturbation of the field by the atmosphere. In particular, we derive expressions for the cross-spectral density of a coherent and a partially coherent beam of arbitrary type in...

It has been generally assumed, since the work of von Karman and Howarth in 1938, that free decay of fully-developed turbulence is self-similar. We present here a simple phenomenological model of the decay of 3D incompressible turbulence, which predicts breakdown of self-similarity for low-wavenumber spectral exponents n in the range nc < n < 4, where nc is some threshold wavenumber. Calculation...