Handan Borluk

A numerical study of the long wave-short wave interaction equations

Two numerical methods are presented for the periodic initial-value problem of the long wave-short wave interaction equations describing the interaction between one long longitudinal wave and two short transverse waves propagating in a generalized elastic medium. The first one is the relaxation method, which is implicit with second-order accuracy in both space and time. The second one is the split-step Fourier method, which is of spectral-order accuracy in space. We consider the first-, second- and fourth-order versions of the split-step method, which are first-, second- and fourth-order accurate in time, respectively. The present split-step method profits from the existence of a simple analytical solution for the nonlinear subproblem. We numerically test both the relaxation method and the split-step schemes for a problem concerning the motion of a single solitary wave. We compare the accuracies of the split-step schemes with that of the relaxation method. Assessments of the efficiency of the schemes show that the fourth-order split-step Fourier scheme is the most efficient among the numerical schemes considered.

A numerical study of the Whitham equation as a model for steady surface water waves

The object of this article is the comparison of numerical solutions of the so-called Whitham equation to numerical approximations of solutions of the full Euler free-surface water-wave problem. The Whitham equation ? t + 3 2 c 0 h 0 ? ? x + K h 0 ? ? x = 0 was proposed by Whitham (1967) as an alternative to the KdV equation for the description of wave motion at the surface of a perfect fluid by simplified evolution equations, but the accuracy of this equation as a water wave model has not been investigated to date.In order to understand whether the Whitham equation is a viable water wave model, numerical approximations of periodic solutions of the KdV and Whitham equation are compared to numerical solutions of the surface water wave problem given by the full Euler equations with free surface boundary conditions, computed by a novel Spectral Element Method technique. The bifurcation curves for these three models are compared in the phase velocity-waveheight parameter space, and wave profiles are compared for different wavelengths and waveheights. It is found that for small wavelengths, the steady Whitham waves compare more favorably to the Euler waves than the KdV waves. For larger wavelengths, the KdV waves appear to be a better approximation of the Euler waves.

Higher order dispersive effects in regularized Boussinesq equation

In this paper, we consider the higher order Boussinesq (HBq) equation which models the bi-directional propagation of longitudinal waves in various continuous media. The equation contains the higher order effects of frequency dispersion. The present study is devoted to the numerical investigation of the HBq equation. For this aim a numerical scheme combining the Fourier pseudo-spectral method in space and a Runge Kutta method in time is constructed. The convergence of semi-discrete scheme is proved in an appropriate Sobolev space. To investigate the higher order dispersive effects and nonlinear effects on the solutions of HBq equation, propagation of single solitary wave, head-on collision of solitary waves and blow-up solutions are considered.

Non-existence and existence of localized solitary waves for the two-dimensional long-wave–short-wave interaction equations

Abstract In this study, we establish the non-existence and existence results for the localized solitary waves of the two-dimensional long-wave–short-wave interaction equations. Both the non-existence and existence results are based on Pohozaev-type identities. We prove the existence of solitary waves by showing that the solitary waves are the minimizers of an associated variational problem.