To simulate the effect of free st ream turbulence on turbulent spot formation, experiments were conducted on the interaction of localized three-dimensional disturbances with the harmonic waves in a laminar boundary layer on a flat plate. Experiments conducted in three-dimensional diverging flow (but zero pressure gradient) show, while individually the disturbances decay downstream, their intera...

We report the experimental results and theoretical analysis of broadband detection of terahertz (THz) waves via electric-field-induced second-harmonic generation in laser-induced air plasma with ultrashort laser pulses. By introducing the second-harmonic component of the white light in the laser-induced plasma as a local oscillator, coherent detection of broadband THz waves with ambient air is ...

The issue of non-destructive characterization of material microstructure with respect to precursors to macroscale damage initiation is addressed. Ultrasonic guided waves are known to be sensitive to material nonlinearity, which is evident through the generation of higher harmonic modes. Thus, nonlinear guided waves have strong potential to identify precursors to macroscale damage and revolution...

Motivated by experimental observations of exotic free surface standing wave patterns in the two-frequency Faraday experiment, we investigate the role of normal form symmetries in the associated pattern-selection problem. With forcing frequency components in ratio m/n, where m and n are coprime integers that are not both odd, there is the possibility that both harmonic waves and subharmonic wave...

We present measurements on parametrically driven surface waves (Faraday waves) performed in the vicinity of a bicritical point in parameter space, where modes with harmonic and subharmonic time dependence interact. The primary patterns are squares in the subharmonic and hexagons in the harmonic regime. If the primary instability is harmonic we observe a hysteretic secondary transition from hexa...

Parametric simultaneous solitary wave (simulton) excitations are shown possible in nonlinear lattices. Taking a one-dimensional diatomic lattice with a cubic potential as an example we consider the nonlinear coupling between the upper cutoff mode of acoustic branch (as a fundamental wave) and the upper cutoff mode of optical branch (as a second harmonic wave). Based on a quasi-discreteness appr...

This study is concerned to check the validity and applicability of a five parameter viscoelastic model for harmonic wave propagating in the non-homogeneous viscoelastic rods of varying density. The constitutive relation for five parameter model is first developed and validity of these relations is checked. The non-homogeneous viscoelastic rods are assumed to be initially unstressed and at rest....

This study considers developing numerical solution techniques for the computer simulations of time-harmonic fluid-structure interaction between acoustic and elastic waves. The focus is on the efficiency of an iterative solution method based on a controllability approach and spectral elements. We concentrate on the model, in which the acoustic waves in the fluid domain are modeled by using the v...

This paper investigates the characteristics of the second harmonic generation of Lamb waves in a plate with quadratic nonlinearity. Analytical asymptotic solutions to Lamb waves are first obtained through the use of a perturbation method. Then, based on a careful analysis of these asymptotic solutions, it is shown that the cross-modal generation of a symmetric second harmonic mode by an antisym...