Sharif Digital Repository

Higher-order effects in three-wave resonant interaction of a surface wave, with a pair of interfacial waves in a two-layer fluid, are studied theoretically. Following an initial rapid growth, the interfacial waves approach a steady state of constant amplitude. An explicit solution is presented for transition to the ultimate state of the interaction. It is shown that for interaction in a wave flume, it is necessary to include a 2nd pair of the interfacial waves, resulting from a reflection of the original pair in the analysis. The effects of different parameters on the dynamics of the interaction are investigated. The results indicate that a faster initial growth does not necessarily lead to... 

The present work is a numerical investigation into the waves generated by a pressure source moving in straight channels with a nonrectangular cross-channel depth profile. Wave fields generated by the moving pressure source are described, and the effects of channel bathymetry on the generated wave characteristics of wave height, wave-breaking location, wave-breaking type and intensity, and peel angle are presented. Four different channel cross-section shapes were investigated, and the results were analyzed. It was concluded that the maximum wave height depended primarily on pressure-source parameters and that the investigated channel shapes did not have a significant effect on the maximum... 

Hydrodynamics of highly nonlinear cnoidal waves and their subsequent strong plunging breakers are among the least understood and most significant issues in coastal engineering. In this work, a weakly compressible smoothed particle hydrodynamics (SPH) formulation is used for the study of the generation and propagation of cnoidal waves and investigation of the characteristics of the induced strong plunging breakers. Numerical results show the capability of the SPH scheme for properly simulating the cnoidal waves. For the case of strong plunging breakers, dynamic and kinematic features of the flow are computed and compared with certain implementations of other numerical techniques. SPH is shown... 

The present study is concerned with the numerical simulation of free-surface waves and wave induced separation in the presence of an intrusion. The results of several simulations are reported. The first study was performed for a NACA0024 surface piercing hydrofoil over a range of several Froude numbers (0.19, 0.37, 0.55), along with wave breaking at Fr = 1.0 The NACA0024 foil was of particular interest, as it almost has no separation at large depths; thus the effect of the free-surface wave and the wave induced separation could be studied. Free- surface waves and wave induced separation results were evaluated and compared with both the available experimental data and the previous numerical... 

Using the ellipsoidal cavity model, the quasi-monoenergetic electron output beam in laser-plasma interaction is described. By the cavity regime the quality of electron beam is improved in comparison with those generated from other methods such as periodic plasma wave field, spheroidal cavity regime and plasma channel guided acceleration. Trajectory of electron motion is described as hyperbolic, parabolic or elliptic paths. We find that the self-generated electron bunch has a smaller energy width and more effective gain in energy spectrum. Initial condition for the ellipsoidal cavity is determined by laser-plasma parameters. The electron trajectory is influenced by its position, energy and...