A Phased Array Doppler Sonar (PADS), as developed at SIO, images both acoustic backscatter intensity and Doppler shift over areas up to 90 degrees in bearing by 500 m in range. Sequences of images are recorded continuously for up to two months, with individual “pings” 0.5 to 1.0 seconds apart. The images permit two independent estimates of the mean velocity to be formed over the imaged area: on...

A global methodology for simulating multiphase flows and heat transfers interacting with complex objects or interfaces is presented. Elliptic equations or Navier-Stokes equations are resolved on a fixed structured curvilinear grid and the solid objects are initially represented by triangular surface elements. Several difficulties arise as soon as these two non-conforming grids have to interact ...

We derive from Eulerian electron beam equations the multifrequency spectral Eulerian (MUSE) model, a new onedimensional (1-D) nonlinear multifrequency model of a traveling wave tube (TWT). We also derive from the same equations a Lagrangian “disk” model, LATTE, so that MUSE may be directly compared to a Lagrangian approach. The models are compared to the large signal code Christine 1-D on a set...

We adopt a recent work in Chung, Qian, Uhlmann and Zhao (Inverse Problems, 23(2007) 309-329) to develop a phase space method for reconstructing pressure wave speed and shear wave speed of an elastic medium from travel time measurements. The method is based on the so-called Stefanov-Uhlmann identity which links two Riemannian metrics with their travel time information. We design a numerical algo...

In this study, we establish a hybrid high-order smoothed particle hydrodynamics (SPH) framework (MLS-TENO-SPH) for compressible flows with discontinuities, which is able to achieve genuine convergence in smooth regions and also capture discontinuities well non-smooth regions. The can be either fully Lagrangian, Eulerian or realizing arbitary-Lagrangian-Eulerian (ALE) feature enforcing the isotr...

We propose a computational method for the coupled simulation of a compressible flow interacting with a thin-shell structure undergoing large deformations. An Eulerian finite volume formulation is adopted for the fluid and a Lagrangian formulation based on subdivision finite elements is adopted for the shell response. The coupling between the fluid and the solid response is achieved via a novel ...

The Eulerian description of an incompressible viscous fluid of constant density and temperature is concerned with the fluid velocity u(x, t) and pressure p(x, t) recorded at fixed positions x ∈ R, n = 3 as functions of time t. The solutions of the incompressible, inviscid Euler equations can be thought of as geodesic paths on an infinite dimensional group of transformations ([1]). This is done ...

We develop a new phase space method for reconstructing the index of refraction of a medium from travel time measurements. The method is based on the so-called Stefanov–Uhlmann identity which links two Riemannian metrics with their travel time information. We design a numerical algorithm to solve the resulting inverse problem. The new algorithm is a hybrid approach that combines both Lagrangian ...

The motion of inertial (i.e., finite-size) particles is analyzed in a three-dimensional unsteady simulation of Hurricane Isabel. As established recently, the long-term dynamics of inertial particles in a fluid is governed by a reduced-order inertial equation, obtained as a small perturbation of passive fluid advection on a globally attracting slow manifold in the phase space of particle motions...

A model of the gravitationally evolved dark matter distribution, in the Eulerian space, is developed. It is a simple extension of the excursion set model that is commonly used to estimate the mass function of collapsed dark matter haloes. In addition to describing the evolution of the dark matter itself, the model allows one to describe the evolution of the Eulerian space distribution of the ha...