The propagation of transient inertio-gravity waves in a shear flow is examined using the Gaussian beam formulation. This formulation assumes Gaussian wavepackets in the spectral space and uses a second-order Taylor expansion of the phase of the wave field. In this sense, the Gaussian beam formulation is also an asymptotic approximation like spatial ray tracing; however, the first one is free of...

The damping of sound waves in magnetized ferrofluids is investigated and shown to be considerably higher than in the nonmagnetized case. This fact may be interpreted as a field-enhanced, effective compressional viscosity-in analogy to the ubiquitous field-enhanced shear viscosity that is known to be the reason for many unusual behaviors of ferrofluids under shear.

The recent theoretical discovery of families of travelling wave solutions in pipe flow (Faisst & Eckhardt 2003; Wedin & Kerswell 2004; Hof et al. 2004) at Reynolds numbers lower than the transitional range naturally raises the question of their relevance to the turbulent transition process. Here a series of numerical experiments are conducted in which we look for the spatial signature of these ...

Long-period surface waves are used to map lateral heterogeneities of velocity and anisotropy in the upper mantle. The dispersion curves are expanded in spherical harmonics up to degree 6 and inverted to find the depth structure. The data are corrected for the effect of surface layers and both Love and Rayleigh waves are used. Shear wave velocity and shear polarization anisotropy can be resolved...

Earth’s rotation causes splitting of normal modes. Wave fronts and rays are, however, not affected by Earth’s rotation, as we show theoretically and with observations made with USArray. We derive that the Coriolis force causes a small transverse component for P waves and a small longitudinal component for S waves. More importantly, Earth’s rotation leads to a slow rotation of the transverse pol...

The purpose of this paper is to synthesize the most important results of the thesis work of Meredith (1990) concerning radiation from seismic sources in boreholes. Previous studies of radiation from sources in boreholes have been far-field studies and have neglected the explicit contribution of the borehole. In general, this is fine for P-wave radiation and for S-wave radiation into high veloci...

We study the motion of a sphere falling through soft viscoelastic materials when the time scale of the motion is short compared to the elastic relaxation time of the material. We observe shocks generated by the passage of the sphere at Mach numbers greater than 1. The sphere can undergo oscillations before reaching a steady terminal speed, and we show that these oscillations have the same frequ...

Receiver functions derived from teleseismic body waves recorded by ocean-bottom seismometers on the southern East Pacific Rise reveal shear waves converted from compressional waves at the mantle discontinuities near 410- and 660-kilometer depth. The thickness of the mantle transition zone between the two discontinuities is normal relative to the global average and indicates that upwelling benea...

The objective of this thesis is to develop a rigorous mathematical and numerical background for the extension and dissemination of imaging modalities by ultrasound, i.e. elastic waves, applied to the cardiac settings. The problems treated will concerned the topics of mathematical modeling, numerical analysis and scientific computing. More precisely we plan to define a linearized model for the p...

A set of Shock Wave Lithotripsy(SWL) related experimental observations including 3D dynamic crack propagation, reported in literature, are simulated with the aim of understanding the fragmentation of kidney stone with SWL. Extracorporeal shock wave lithotripsy (ESWL) is the fragmentation of kidney stones by focusing an ultrasonic pressure pulse onto the stones. 3D models with fine discretizatio...