A high-order semi-explicit discontinuous Galerkin solver for 3D incompressible flow with application to DNS and LES of turbulent channel flow

We present an efficient discontinuous Galerkin scheme for simulation of the incompressible Navier-Stokes equations including laminar and turbulent flow. We consider a semi-explicit high-order velocity-correction method for time integration as well as nodal equal-order discretizations for velocity and pressure. The non-linear convective term is treated explicitly while a linear system is solved for the pressure Poisson equation and the viscous term. The key feature of our solver is a consistent penalty term reducing the local divergence error in order to overcome recently reported instabilities in spatially under-resolved high-Reynolds-number flows as well as small time steps. This penalty method is similar to the grad-div stabilization widely used in continuous finite elements. We further review and compare our method to several other techniques recently proposed in literature to stabilize the method for such flow configurations. The solver is specifically designed for large-scale computations through matrix-free linear solvers including efficient preconditioning strategies and tensor-product elements, which have allowed us to scale this code up to 34.4 billion degrees of freedom and 147,456 CPU cores. We validate our code and demonstrate optimal convergence rates with laminar flows present in a vortex problem and flow past a cylinder and show applicability of our solver to direct numerical simulation as well as implicit large-eddy simulation of turbulent channel flow at $Re_{\tau}=180$ as well as $590$.Comment: 28 pages, in preparation for submission to Journal of Computational Physic

Why do Healthcare Organizations Choose to Violate Information Technology Privacy Regulations? Proposing the Selective Information Privacy Violations in Healthcare Organizations Model (SIPVHOM)

Privacy concerns about protected healthcare information (PHI) are rampant because of the ease of access to PHI from the advent of Healthcare IT (HIT) and its exploding use. Continual negative cases in the popular attest to the fact that current privacy regulations are failing to keep PHI sufficiently secure in the climate of increate HIT use. To address these issues, this paper proposes a theoretical model with testable hypotheses to explain and predict organizational IT privacy violations in the healthcare industry. Our model, the Selective Information Privacy Violations in Healthcare Organizations Model (SIPVHOM), explains how organizational structures and processes and characteristics of regulatory environments alter perceptions of risk and thereby the likelihood of rule violations. Finally, based on SIPVHOM, we offer recommendations for the structuring of regulatory environments and organizational structures to decrease abuse of PHI

Monitoring 35S During the Incineration of Liquid Low Level Radioactive Waste

Effluents and residual ash were monitored in order to determine the fate of 35S labelled liquid waste during high temperature incineration. Effluents were monitored using a modified EPA approved Method 5 isokinetic sampling probe with 3% H2O2 as the trapping solution. The radioactivity content in the gaseous effluents and residual ash was counted using a liquid scintillation counter calibrated for 35S. Eleven trial burns of liquid waste with activities ranging from 199 to 5659 μCi^1 were conducted. An aqueous solution of 35S labelled Methionine was the source of activity in eight of the trials and an aqueous solution of 35S labeled sulphate was the source in the remaining three trials. Percent of the total activity incinerated contained in the effluents and ash was determined.Master of Science in Public Healt