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!
Last Wednesday, Ahmad Eter presented his PhD seminar work on “flow obstruction effects on heat transfer in channels at supercritical and high subcritical pressures”. Supervisor Dr. Stavros Tavoularis was present, although co-supervisor Dr. Groeneveld could not attend. I got a few pics of Ahmad with his supervisor.
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
Room: CBY B205
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.
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.
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.
To kick off the first seminar of our summer seminar series, Saeed Rahbarimanesh presented his talk on the direct numerical simulation of mixing layers. Supervisor Dr. Catherine Mavriplis was in attendance along with a small but alert crowd. Something about coffee and cookies keeps people alert in the morning…
Laura presented a really interesting talk on flow measurements through a bileaflet mechanical heart valve in an anatomical model of the aorta. Supervisor Dr. Tavoularis was on hand for moral support, cookie munching and a photo op. This was a well-attended last seminar of our winter Friday seminar series. Looking forward to next semester!
On Monday March 30th, Dr. Mavriplis will host a Canadian Aeronautics and Space Institute event, featuring:
Imane El karafi, M. Eng., PW800 Controls Systems, Pratt & Whitney Canada
Experiences of a Young Engineer at Pratt & Whitney Canada
Location: 161 Louis Pasteur, Colonel By Building – Room A707
5:30 – 6:00 pm: Meet and Greet for CASI Members and Invitees
Drinks and snacks will be served.
6:00 – 7:00 pm: Presentation
7:00 – 7:30 pm: Question and Answer Session
Imane has been working at Pratt & Whitney Canada (P&WC) since 2010. Her experience has provided skills in engineering for engine assembly preparation and certification, engine testing on the ground and in flight, project management and sustainable development. Starting in 2015, Imane embraces a new role in Controls Systems within the revolutionary turbofan engine family PW800.
Academically, Imane graduated in 2010 with a double major in Mechanical and Information Technology from the University of Ottawa. In September 2014, Imane started an Executive Master’s in Business Administration at the University of Sherbrooke Campus of Longueuil.
As part of the CASI talk, Imane will be presenting the exciting opportunities she experienced at P&WC in the engineering disciplines and the challenges”young engineer” faces in the professional function of today.
The brand new PW800 engine was just certified in February for flight on a new Gulfstream aircraft.
All students welcome!
RSVP to Catherine Mavriplis at Catherine.Mavriplis@uottawa.ca
Amir presented his MASc thesis work last Friday on “Development and Implementation of a Preconditioner for a Five-Moment One-Dimensional Moment Closure”. Supervisor Dr James McDonald was on hand for the presentation.
Traditionally, the Euler or Navier-Stokes equations are used to describe the time-evolution of a gas in the continuum regime. However, when a gas leaves the continuum regime and non-equilibrium effects become significant, neither of those two models produce physically accurate predictions.
Recently, a new system of first-order hyperbolic partial differential equations (PDEs) was proposed for the treatment of monatomic gases that is valid both in and for significant departures from local thermal equilibrium. In this study, the resulting system for a one-dimensional gas is studied. It consists of first-order hyperbolic PDEs. The numerical computation ofvthe system has proven to be difficult since, for some realistic states, the closing flux of the system becomes infinitely large. In the present study, the technique of preconditioning is used to develop a preconditioner for the system to scale the closing flux in order to remove the infinity from the system without altering the solution of the system in any way. A numerical implementation of the preconditioned system is described. Numerical solutions of several continuum and non-equilibrium flows problems are shown. Comparisons are made with other classical models.
Special Seminar! Speaker: Professor Dan Henningson, Royal Institute of Technology, Sweden
DATE: Friday February 6th, 2015
Location: University of Ottawa
Colonel By Pavilion, Room D207, 161 Louis Pasteur
2:30-‐3:30 pm: Presentation
3:30-‐4:00: Question and Answer Session
Abstract: Recent work within a number of EU-‐projects have shown that laminar flow can significantly reduce drag and fuel consumption of modern transport aircraft. Methods include the application of suction on the wing surface and the modification of the wing geometry in order to minimize growth of disturbances that causes laminar-‐turbulent transition. Efficient optimization of suction distributions and wing shapes can be performed using so called adjoint methods from optimal control theory. It is shown that such suction distributions and wing shapes significantly increases the laminar regions of wings on transport aircraft. Such optimization tools are now used in the next generation of laminar flow projects, such as the EU Joint Technology Initiative Clean Sky. Showstoppers and an outlook for future work will also be presented.
Dr. Henningson’s research and professional activities include Research on linear and nonlinear hydrodynamic stability and numerical simulation of transitional and turbulent flow. His academic background is Civ.Ing KTH 1983, M.Eng MIT 1985, PhD KTH 1988, Docent KTH 1992, while his professional history incudes Research Scientist FFA 1985-‐. Ass. Prof. Appl. Math. MIT 1988-‐1992. Adj. Prof. Mechanics (20%) KTH 1992-‐1998. Lektor Mechanics (50%) 1998-‐1999.
This event is being organized in collaboration with the University of Ottawa and the Carleton Mechanical and Aerospace Society (CMAS).