Some numbers that are given on page 15771 do not correspond to the velocity distributions shown in Fig. 4. In the third paragraph of this page it should read ‘‘The distribution has a width (FWHM) of 4.8 m s 1 and 1.4 m s 1 in the longitudinal and transverse direction, respectively. The velocity distribution can also be expressed as a speed ratio of S = 235 (or a temperature of T = 15.0 mK) and ...

We study the homogenization limit of solutions to the G-equation with random drift. This Hamilton-Jacobi equation is a model for flame propagation in a turbulent fluid in the regime of thin flames. For a fluid velocity field that is statistically stationary and ergodic, we prove sufficient conditions for homogenization to hold with probability one. These conditions are expressed in terms of tra...

Christof Koch [email protected] We describe two parallel analog VLSI architectures that integrate optical flow data obtained from arrays of elementary velocity sensors to estimate heading direction and time-to-contact. For heading direction computation, we performed simulations to evaluate the most important qualitative properties of the optical flow field and determine the best functional ...

We introduce and analyze a discontinuous Galerkin method for the incompressible Navier-Stokes equations that is based on finite element spaces of the same polynomial order for the approximation of the velocity and the pressure. Stability of this equal-order approach is ensured by a pressure stabilization term. A simple element-by-element postprocessing procedure is used to provide globally dive...

This paper takes a fresh look at the Geometric Conservation Law (GCL) from the perspective of Arbitrary Lagrangian Eulerian (ALE) finite element methods for solving 3-D incompressible viscous flows problems on deforming domain. GCL compliance is traditionally interpreted as a consistency criterion for applying an unsteady flow solution algorithm to simulate exactly a uniform flow on a deforming...

We consider the mixing behaviour of the solutions of the continuity equation associated with a divergence-free velocity field. In this announcement we sketch two explicit examples of exponential decay of the mixing scale of the solution, in case of Sobolev velocity fields, thus showing the optimality of known lower bounds. We also describe how to use such examples to construct solutions to the ...

Conventional least squares finite element methods (LSFEM) for incompressible flows conserve mass approximately. In some cases, this can lead to an unacceptable loss of mass and unphysical solutions. In this report we formulate a new, locally conservative LSFEM for the Stokes equations which computes a discrete velocity field that is point-wise divergence free on each element. To this end, we em...

We show that modes of axially uniform waveguides of arbitrary cross section can be made to have anomalous dispersion relations resulting from strong repulsion between two modes. When the axial wave vector k is 0, the two modes have different TE/TM symmetry and thus can be brought arbitrarily close to an accidental frequency degeneracy. For nonzero k, the symmetry is broken causing the modes to ...

We consider the solution of the discrete linear system resulting from a mixed finite element discretization applied to a second-order elliptic boundary value problem in three dimensions. Based on a decomposition of the velocity space, these equations can be reduced to a discrete elliptic problem by eliminating the pressure through the use of substructures of the domain. The practicality of the ...

The characteristic-based split (CBS) method has been widely used in the finite element community to facilitate the numerical modeling of the Navier-Stokes equations. In this paper a CBS-based finite volume algorithm is introduced for the solution of incompressible Navier-Stokes equations. The proposed method is implemented on a co-located grid arrangement and employs a transient fractional step...