Learn More
Efficient solution of the Navier-Stokes equations in complex domains is dependent upon the availability of fast solvers for sparse linear systems. For unsteady incompress-ible flows, the pressure operator is the leading contributor to stiffness, as the characteristic propagation speed is infinite. In the context of operator splitting formulations, it is the(More)
We study the performance of the multigrid method applied to spectral element (SE) discretizations of the Poisson and Helmholtz equations. Smoothers based on finite element (FE) discretizations, overlapping Schwarz methods, and point-Jacobi are considered in conjunction with conjugate gradient and GMRES acceleration techniques. It is found that Schwarz(More)
Overflows are bottom gravity currents which supply dense water masses generated in high-latitude and marginal seas into the general circulation. In light of oceanic observations which indicate that mixing of overflows with ambient water masses takes place over small spatial and time scales, and studies with ocean general circulation models, which indicate(More)
Projection techniques are developed for computing approximate solutions to linear systems of the form Ax n = b n , for a sequence n = 1; 2; :::, e.g., arising from time discretization of a partial diierential equation. The approximate solutions are based upon previous solutions, and can be used as initial guesses for iterative solution of the system,(More)
We present a high-order discontinuous Galerkin discretization of the unsteady in-compressible Navier-Stokes equations in convection-dominated flows using triangular and tetrahedral meshes. The scheme is based on a semi-explicit temporal discretization with explicit treatment of the nonlinear term and implicit treatment of the Stokes operator. The nonlinear(More)
We develop a fast direct solver for parallel solution of \coarse grid" problems, Ax = b, such as arise when domain decomposition or multigrid methods are applied to elliptic partial diierential equations in d space dimensions. The approach is based upon a (quasi-) sparse factorization of the inverse of A. If the dimension of the system is n and the number(More)
We present experimental and computational results that describe the level, distribution, and importance of velocity fluctuations within the venous anastomosis of an arteriovenous graft. The motivation of this work is to understand better the importance of biomechanical forces in the development of intimal hyperplasia within these grafts. Steady-flow in(More)
We describe the development and implementation of an efficient spectral element code for simulating transitional flows in complex three-dimensional domains. Critical to this effort is the use of geometrically nonconforming elements that allow localized refinement in regions of interest, coupled with a stabilized high-order time-split formulation of the(More)
In light of the pressing need for development and testing of reliable parameterizations of gravity current entrainment in ocean general circulation models, two existing entrainment parameterization schemes, K-profile parameterization (KPP) and one based on TurnerÕs work (TP), are compared using idealized experiments of dense water flow over a constant-slope(More)