Adaptive mesh strategies for the spectral element method

An adaptive spectral method was developed for the efficient solution of time dependent partial differential equations. Adaptive mesh strategies that include resolution refinement and coarsening by three different methods are illustrated on solutions to the 1-D viscous Burger equation and the 2-D Navier-Stokes equations for driven flow in a cavity. Sharp gradients, singularities, and regions of poor resolution are resolved optimally as they develop in time using error estimators which indicate the choice of refinement to be used. The adaptive formulation presents significant increases in efficiency, flexibility, and general capabilities for high order spectral methods

Initiatives to Empower Women Faculty Members at University of Ottawa: Mothers See the Value in Participation

Despite the increasing number of female students in undergraduate and graduate programs, female faculty members are still a minority at most Canadian universities. Although participation by women has increased significantly at the pre-tenure assistant rank, substantial gaps between the number of men and women at the associate and full professor levels remain as well as for research chairs and leadership roles. This article describes the multiple initiatives put in place at the University of Ottawa to support women faculty members in their careers, a great majority of whom are mothers, trying to balance professional and family responsibilities. The policies include long-standing Policy 94 named for its year of inception, a number of career and leadership development activities through the Centre for Academic Leadership established in 2005, and tailored activities through the nserc / Pratt & Whitney Canada Chair for Women in Science and Engineering program (2011- 2016). Although not all of these activities were geared towards women and mothers, the participants, overwhelmingly, have turned out to be mothers or have expressed the desire to become mothers. Among these current and aspiring women professors, many are unsure of how to combine an academic career with motherhood. A short portrait of the activity participants and their reflections are included in the paper. In particular, responses from mothers who, as professors, attended the Centre for Academic Leadership writing retreats indicate that their participation was influenced by their family responsibilities; these mothers cited the particular usefulness of the activity for writing productivity

Spectral Element Simulations of Laminar Diffusion Flames

this paper we present spectral element simulations of laminar axisymmetric non-premixed methaneair diffusion flames. The spectral element method [Pat84] is a high-order domain decomposition method which is used in the solution of time-dependent nonlinear partial differential equations. The method has been used in the solution of the NavierStokes equations for direct simulation of fluid flow, e.g. [Kar90, FR94]. Here, we extend the Navier-Stokes solver to include chemistry and energy conservation equations. This paper is the first attempt at establishing our simulation capability for laminar diffusion flames. Results are compared with theoretical and experimental flame

Red blood cell aggregates and their effect on non-Newtonian blood viscosity at low hematocrit in a two-fluid low shear rate microfluidic system.

Red blood cells (RBCs) are the most abundant cells in human blood. Remarkably RBCs deform and bridge together to form aggregates under very low shear rates. The theory and mechanics behind aggregation are, however, not yet completely understood. The main objective of this work is to quantify and characterize RBC aggregates in order to enhance the current understanding of the non-Newtonian behaviour of blood in microcirculation. Suspensions of human blood were flowed and observed in vitro in poly-di-methyl-siloxane (PDMS) microchannels to characterize RBC aggregates. These microchannels were fabricated using standard photolithography methods. Experiments were performed using a micro particle image velocimetry (μPIV) system for shear rate measurements, coupled with a high-speed camera for flow visualization. RBC aggregate sizes were quantified in controlled and measurable shear rate environments for 5, 10 and 15% hematocrit. Aggregate sizes were determined using image processing techniques, while apparent viscosity was measured using optical viscometry. For the samples suspended at 5% H, aggregate size was not strongly correlated with shear rate. For the 10% H suspensions, in contrast, lowering the shear rate below 10 s-1 resulted in a significant increase of RBC aggregate sizes. The viscosity was found to increase with decreasing shear rate and increasing hematocrit, exemplifying the established non-Newtonian shear-thinning behaviour of blood. Increase in aggregation size did not translate into a linear increase of the blood viscosity. Temperature was shown to affect blood viscosity as expected, however, no correlation for aggregate size with temperature was observed. Non-Newtonian parameters associated with power law and Carreau models were determined by fitting the experimental data and can be used towards the simple modeling of blood's non-Newtonian behaviour in microcirculation. This work establishes a relationship between RBC aggregate sizes and corresponding shear rates and one between RBC aggregate sizes and apparent blood viscosity at body and room temperatures, in a microfluidic environment for low hematocrit. Effects of hematocrit, shear rate, viscosity and temperature on RBC aggregate sizes have been quantified

Unstructured Adaptive (UA) NAS Parallel Benchmark

We present a complete specification of a new benchmark for measuring the performance of modern computer systems when solving scientific problems featuring irregular, dynamic memory accesses. It complements the existing NAS Parallel Benchmark suite. The benchmark involves the solution of a stylized heat transfer problem in a cubic domain, discretized on an adaptively refined, unstructured mesh

Optimal disturbances above and upstream a flat plate with an elliptic leading edge

Adjoint-based iterative methods are employed in order to compute linear optimal disturbances in a spatially growing boundary layer around an elliptic leading edge. The Lagrangian approach is used where an objective function is chosen and constraints are assigned. The optimisation problem is solved using power iterations combined with a matrix-free formulation, where the state is marched forward in time with a standard DNS solver and backward with the adjoint solver until a chosen convergence criterion is fulfilled. We consider the global and the upstream localised optimal initial condition leading to the largest possible energy amplification at time T. We found that the twodimensional initial condition with the largest potential for growth is a Tolmien-Schlichting-like wave packet that includes the Orr mechanism and is located inside the boundary layer, downstream of the leading edge. Three-dimensional disturbances induce streaks by the lift-up mechanism. Localised optimal initial condition enables us to better study the effects of the leading edge; with this approach we propose a new method to study receptivity. Two-dimensional upstream disturbances, are inefficient at triggering an unstable eigenmode. The three-dimensional disturbances instead induce elongated streamwise streaks; both the global and upstream localised disturbances give significant growth. This advocates for high receptivity to three-dimensional disturbances.QC 2011051