Jason S. Howell

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There have been many numerical simulations but few analytical results of stability and accuracy of algorithms for computational modeling of fluid-fluid and fluid-structure interaction problems, where two domains corresponding to different fluids (ocean-atmosphere) or a fluid and deformable solid (blood flow) are separated by an interface. As a simplified(More)
BACKGROUND Anergia (lack of energy) is a newly delineated, criterion-based geriatric syndrome. Because heart failure (HF) is a common chronic condition among older adults and a because a cardinal symptom of HF is reduced energy, we characterized the degree of anergia in subjects with HF and evaluated its relevance to disease severity, functional(More)
Necessary and sufficient conditions for existence and uniqueness of solutions are developed for twofold saddle point problems which arise in mixed formulations of problems in continuum mechanics. This work extends the classical saddle point theory to accommodate nonlinear constitutive relations and the twofold saddle structure. Application to problems in(More)
OBJECTIVES To compare the correlation between the maximum 6 minutes of daily activity (M6min) and standard measures of functional capacity in older adults with heart failure (HF) with that in younger subjects and its prognostic utility. DESIGN Prospective, cohort study. SETTING Tertiary care, academic HF center. PARTICIPANTS Sixty, ambulatory, adults,(More)
In this work a dual-mixed approximation of a nonlinear generalized Stokes problem is studied. The problem is analyzed in Sobolev spaces which arise naturally in the problem formulation. Existence and uniqueness results are given and error estimates are derived. It is shown that both lowest-order and higher-order mixed finite elements are suitable for the(More)
The numerical simulation of viscoelastic fluid flow becomes more difficult as a physical parameter, the Weissenberg number, increases. Specifically, at a Weissenberg number larger than a critical value, the iterative nonlinear solver fails to converge. In this paper a two-parameter defect-correction method for viscoelastic fluid flow is presented and(More)
In this work a finite element method for a dual-mixed approximation of Stokes and nonlinear Stokes problems is studied. The dual-mixed structure, which yields a twofold saddle point problem, arises in a formulation of this problem through the introduction of unknown variables with relevant physical meaning. The method approximates the velocity, its(More)
A mixed finite element method for the Navier–Stokes equations is introduced in which the stress is a primary variable. The variational formulation retains the mathematical structure of the Navier–Stokes equations and the classical theory extends naturally to this setting. Finite element spaces satisfying the associated inf–sup conditions are developed.(More)
Abstract. A model of two incompressible, Newtonian fluids coupled across a common interface is studied. The nonlinearity of the coupling condition exacerbates the problem of decoupling the fluid calculations in each subdomain, a natural parallelization strategy employed in current climate models. A specialized partitioned time stepping method is studied(More)