Francois Forgues presented his thesis seminar

Last Friday, MASc candidate Francois Forgues present his thesis seminar titled “Higher-Order Moment Models for Laminar Multiphase Flows Coupled to a Background Gas”. Supervisor Dr. James McDonald was present for the seminar and obligatory photo op. Thanks, both! Well done, Francois!

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Alireza Miri presented his thesis seminar

Last Friday, Seyed Alireza Miri presented his thesis seminar titled “Numerical Solution of Moment Equations Using a Discontinuous-Galerkin Hancock Method”. Supervisor Dr. James McDonald was present for the seminar and the photo-op. Congrats Alireza!

Closing out 2016 – Aurelian Tanase presented his seminar

Last but not least for 2016, Aurelian Tanase presented his PhD thesis seminar, with PhD work completed under the supervision of Drs. Tavoularis and Groeneveld. The title of the talk was “flow and heat transfer in tubes with objects”.It was an interesting talk, followed by some delicious shawarma to round out our fall semester. Congrats Aurelian and here’s to 2017!

Next seminar on Friday!

Rym Mehri will present her PhD thesis seminar this coming Friday.  She will be giving a talk on “Investigation and Characterization of Red Blood Cells Aggregation: Experimental and Numerical Study”.   The talk abstract is below.  All are welcome!

Date: Friday March 4

Time: 2:30pm

Room: CBY B205

 

Abstract

Red blood cells (RBC) are the most abundant cells in human blood, representing 40 to 45% of the blood volume (hematocrit). These cells have the particularity to deform and bridge together to form aggregates under very low shear rates. Due to their unique mechanical properties, RBCs represent the focus of numerous experimental and numerical studies, especially, at the microscopic level. In fact, the theory and mechanics behind aggregation are not yet completely understood. Understanding the conditions of aggregate formation could provide a better understanding of the mechanics behind this phenomenon and could help to determine aggregate behaviour related to clinical application such as diabetes and heart disease.

 
The purpose of this work is to provide a novel method to analyze, understand and mimic blood behaviour in the microcirculation. The main objective is to develop a methodology in order to quantify and characterize RBC aggregates and hence comprehend the non-Newtonian behaviour of blood at the microscale. For this purpose, suspensions of porcine blood and human blood are tested in vitro in a Polydimethylsiloxane (PDMS) microchannel to characterize the RBC aggregates. These microchannels are fabricated using standard photolithography methods. Experiments are performed using a micro Particle Image Velocimetry (μPIV) system for shear rate measurements coupled with a high speed camera for the flow visualization. Corresponding numerical simulations are conducted using a research Computational Fluid Dynamic (CFD) Solver, Nek5000, based on the spectral element method.

 

RBC aggregate sizes are quantified in controlled and measurable shear rates environments for 5, 10 and 15% hematocrit. Aggregate sizes are determined using image processing techniques. Velocity fields of the blood flow are measured experimentally and compared to numerical simulations using simple non-Newtonian models (Power law and Carreau models).

This work establishes for the first time a relationship between RBC aggregate sizes and corresponding shear rates as well as one between RBC aggregate sizes and apparent blood viscosity at body temperature. The results of the investigation can be used to help develop new numerical models for non-Newtonian blood flow.

Armel Don is up next – Tuesday at 10am!

Come hear Armel Don present his thesis seminar on “Structure of Turbulent Flow in a Rod Bundle”.

OMEGA is offering tea, coffee and cookies. We’ll be in CBY B012 at 10:00am.  The abstract of Armel’s talk is below.

Abstract

The core of the CANadian Deuterium Uranium (CANDU) nuclear reactor consists of several pressure tubes containing bundles of fuel elements (“rods”) stacked end to end. The fuel rods are cooled by liquid coolant (heavy water) flowing axially in the interconnected subchannels formed by the rods. The thermal-hydraulic performance of the reactor, and particularly the surface temperature of the rods and the temperature of the coolant depend strongly on the turbulent flow structure in the subchannels.

Typically, the Reynolds number of a CANDU reactor running at full power is about half a million. During start-up or shut down, the Reynolds number drops to a much lower value and tends to fluctuate. Although a large number of experimental and computational studies have examined flows in rod bundles, the effect of Reynolds number on the structure of turbulence and the development of vortex networks have not been documented sufficiently.

This experiment aims at investigating experimentally the structure of turbulent flow in the subchannels of a large scale, 60o section of a CANDU 37-rod bundle at Reynolds numbers equal to 50,000, 100,000 and 130,000. The mean flow distribution, the turbulent kinetic energy, the Reynolds stresses, coherent structure characteristics and other turbulence indicators were measured using constant temperature hot-wire anemometry. It was demonstrated that coherent structures, whose generation is attributed to the gap instability mechanism and which form a vortex network, originated very close to the rod bundle inlet. The convection speed of the vortex network increased with bulk velocity, whereas the spacing between the coherent vortices remained unaffected.