Current opportunities for graduate students - enquiries welcome

prof picture

Iakov Afanassiev (Yakov Afanasyev)


Professor
Experimental Oceanic and Atmospheric Fluid Dynamics;
Numerical Modelling of Geophysical Flows

Coordinates:
Telephone: (709) 864-2500
Fax: (709) 864-8739
Office: C-4065
Lab:1046
Email: afanai at mun.ca

Address: Department of Physics and Physical Oceanography
Memorial University of Newfoundland
St. John's, NL
A1B 3X7, Canada

Research Laboratory Publications Book Students Student Projects Courses Links Fluid Dynamics Gallery Press Oil paintings: Portraits, Landscape and Still Life

 


Brief CV

M.Sc., School of Aerophysics and Space Research, Moscow Institute of Physics and Technology (1986)
Ph.D., P.P.Shirshov Institute of Oceanology Russian Academy of Sciences (1989)
Research Associate,P.P.Shirshov Institute of Oceanology Russian Academy of Sciences (1989-95)
Post-Doctoral Research Associate, Atmospheric Physics, University of Toronto (1995-99)
Assistant Professor (1999-2003), Associate Professor (2003-2009), Professor (2009-) Department of Physics and Physical Oceanography, Memorial University of Newfoundland


Research Interests

My overall research objective is to better understand the dynamical processes that govern the behavior of the stratified and rotating fluid that comprise the Earth's oceans, so as to improve upon existing capacity to predict evolution of complex geophysical fluid dynamical processes. In pursuing this goal I have come to rely upon an approach combining theoretical, experimental and numerical techniques. This is an exciting area of research, as it gives us insight into fundamental oceanic and atmospheric physics, and also has relevance to our interaction with the environment.

Current projects:



Picture above shows evolution of thermally induced turbulence on a polar beta-plane, as seen from above the North pole (the center). Color shows the surface elevation field. The bottom is heated along a radius, and the convective turbulence generates zonal circulation in turbulent beta-plumes, which involve Rossby-wave signalling westward from the energy source. Visualized with optical altimetry which displays surface height variations of a few microns (millionths of a meter). Physics Today inside back cover, October 2011. Ocean/atmosphere experiments on a rotating table use the parabolic water surface to simulate the polar cap of the planet.

I am creating a library of videos which can be used for demonstrations in oceanography or geophysical fluid dynamics. Check them out at Youtube:

OPTICAL ALTIMETRY: IMAGING THE PRESSURE, VELOCITY AND VORTICITY IN A ROTATING FLUID

NEWS! A complete software package for analysis of AIV (color altimetric images) is now available. Once the system is assembled (involving a color transparency and a light source and camera mounted above the rotating table, or with mirror  mounted halfway above the fluid in the laboratories with low ceiling), this software makes efficient calculations of surface height field, geostrophic and ageostrophic pressure and velocity, and vorticity and potential vorticity. Contact yakov@physics.mun.ca

I am back from sabbatical where I was working with Peter Rhines at the University of Washington . Here are a few movies and pictures of our recent results:
"Designer planets" Atmosphere (ocean) in a soap bubble:

eye_bubble_Afanasyev2006.jpg

The iris of this eye  is an experimental image of a large soap bubble (diameter 30 cm). The soap bubble when placed on a rapidly rotating platform  can model  a planetary atmosphere or an ocean. Convective motions within the bubble create color pattern due to interference of light.

For  10mb wmv movie (with sound) of rotating soap bubbles  click here.

baroclinic instability of anticyclonic vortex Afanasyev2006

Experimental image of a phenomenon which occurs often in oceans and atmosphere. This phenomenon is called baroclinic instability. The image is obained by  a new  method of color altimetry developed recently in collaboration with the University of Washington.

For  2mb wmv movie of a rotating flow over a mountain illustrating Rossby and inertia waves click
here.

Wakes behind towed and self propelled bodies in 2D and 3D
Theoretical, numerical and laboratory investigation of wakes behind moving forcing of different configurations. Applications include flying insects and birds, swimming microorganisms and fish, wakes behind submarines and bluff bodies.

wake

 

wake

Flight in a viscous fluid.
Experimental image of a flow modelling the vortical wake behind a hydrodynamic model of a small insect. This image won  1st prize at the recent Art of Physics competition of
Canadian Association of Physicists.
This picture shows the wake behind a “virtual” insect flying in fluid. The model of the insect is translated in water horizontally. It has a permanent magnet in its rear end which provides a magnetic field in the direction of motion. At the same time the electric current flows between two electrodes in a perpendicular direction in the horizontal plane. The resulting Lorentz force on the fluid is perpendicular to both the current and the magnetic field and acts in the vertical direction. This force, if applied impulsively during some time intervals, simulates the lift force applied by the flapping wings of an insect during downstrokes. This force transfers momentum downwards while the reaction to this force supports the insect in the air. Momentum transfers in the form of vortex rings. These “rings” look like a Greek letter
W and are connected to each other. The insect is small and the viscosity of the fluid is important. As a result the vortex tubes diffuse in the fluid.  

 

 

Topographic flows, mixing and transport in fjords

Recent interests have included numerical modeling of unstable internal gravity waves, using a fully three-dimensional ``state-of-the-art'' numerical model on various Cray vector supercomputers. The most interesting and dynamically significant effect of internal wave propagation in a stratified fluid arises when the wave achieves such amplitude that it becomes subject to a local convective instability. This is commonly referred as ``wave breaking'' and it is thought to be associated with the transfer of momentum from the wave field to the main flow. The oceanographic examples include flows in coastal inlets subject to gradually changing tidal currents (e.g. Newman Sound, NF; Knight Inlet, BC). Such fjords are typical features of the Newfoundland coast and many of them are used for aquaculture. Thus the study of mixing and forcing of circulation is also of great importance for biological applications. A significant new study devoted to understanding this interesting oceanic nearshore process is currently under way and will be continued. A field study will be considered at a later stage of the project.

Mixing and transport by vortices in a rotating stratified fluid

Vortex structures such as monopoles, dipoles as well as more complex structures are fundamental elements of geophysical turbulence. Because they can effectively transport momentum, heat, salt and biochemical products, they play an essential role in ocean dynamics, determining the instantaneous fields of velocity, temperature and salinity, i.e. so-called internal oceanic weather. A very efficient tool for the investigation of vortices clearly consists of laboratory experimentation. The following specific projects are under way: vortex formation in coastal flows; stability of barotropic vortices in a rotating stratified fluid; dynamics and interactions of vortex structures on a ``beta-plane''. The experimental part of these projects includes setup of PIV (Particle Image Velocimetry) system for the computerized measurements of flow fields. In the framework of this research stream I also plan to initiate a project in collaboration with colleagues from the P.P.Shirshov Institute on thermal variability of the waters of the Newfoundland shelf using satellite SST data.


Graduate Students

Vasily Korabel  (2001-2005)

Jennifer Wells (2002-2005)

Enquiries welcome! Feel free to contact me by email yakov@physics.mun.ca

Details of graduate studies in Physics and Physical Oceanography at Memorial University can be found here

Previous:

Krista Galway (NSERC summer student 2004,co-supervised with Daniel Bourgault) Bariclinic instability in the Gaspe Current (Gulf of St. Lawrence): Laboratory experiments

Marina Blokhina (M.Sc. 2003) Mesoscale Variability in the Black Sea: Satellite Observations and Laboratory Experiments

Shawn Chatman (physics honors student 2001) Analysis of velocity field from satellite images of the ocean

Kylie Gould (physics honors student 2001) Spontaneous emission of inertia-gravity waves by interacting vortices

Fuad Nammas (2000)

Pavel Potylitsin (1994)


Undergraduate Research Students

Enquiries welcome!

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Student Projects

Two-dimensional turbulence - Jennifer Wells (summer student, physics honors student 2001). See also our recent publication J. Wells, Y.D. Afanasyev: Decaying quasi-two-dimensional turbulence in a rectangular container: laboratory experiments, Geophys. Astrophys. Fluid Dynamics

<>Two-dimensional turbulence can be modified significantly when the Coriolis parameter varies with latitude such as that on the rotating Earth. The vortices that comprise the turbulent flow are found to distribute themselves in such a way that they form zonal jets.  Such zonal jets have been observed in many geophysical systems and are a common feature in the atmospheres of Jupiter, Saturn and the Earth.  This picture shows vorticity (color) and velocity (arrows) fields measured during a laboratory experiment on quasi-two-dimensional turbulence on a polar beta-plane. A well-defined polar vortex can be clearly seen in the center of the picture surrounded by an intense cyclonic jet that is subject to Rossby waves.
Afanasyev, Y. D. and Wells, J., "Quasi-two-dimensional turbulence on the polar beta-plane: laboratory experiments", Geophys. Astrophys. Fluid Dynamics, 99 (1), 1-17 (2005).

 

<>
This picture shows the baroclinic instability of a coastal gravity current visualized by dye. Our experiments were carried out using a scaled model of the Black Sea mounted on a rotating table to simulate the effects of the Earth’s rotation. The tank was filled with saline water while the source of fresh dyed water was located in the lower right hand corner of the model. The source allowed us to simulate the supply of fresh water by rivers in the western part of the Black Sea. The fresh water is then transported in cyclonic direction around the sea forming the so-called Rim Current. The current becomes unstable due to the baroclinic instability and forms meanders and vortices. Arrow in the picture indicates the pairing of two vortices. <>(Blokhina, M. D. and Y. D. Afanasyev: Baroclinic instability and transient features of mesoscale surface circulation in the Black Sea: laboratory experiment, J. Geophys. Res.  Oceans, 2003, 108 (C10), 3322, doi:10.1029/3003JC001979).


Courses

Lecture Courses:

Fall 2011: Physics 6363 - - Laboratory Experiment in Geophysical Fluid Dynamics. The objective of this course is to give the student the theoretical basis of the laboratory experimentation in Geophysical Fluid Dynamics through lectures as well as practical skills. This will include the development and implementation of your own fluid dynamics experiment to study a problem that interests you, the results of which will be reported in a paper and video which you will create. Prerequisite(s): P4205 or AMAT 4180 Lectures: Three hours per week.

Fall 2012: Physics 6316 - Ocean Measurements and Data Analysis. Measurement principles, time-series analysis methods, application of these methods to oceanographic data. Lectures: Three hours per week.

Fall 2010: 3500 - Electromagnetic fields I Lectures: Three hours per week.

Winter 2012: 2055 - General Physics VI: Electricity and Magnetism. Prerequisite(s): Mathematics 2000, Physics 1051. Math 2000 may be taken concurrently. Lectures: Three hours per week. Laboratory: Three hours per week.

Fall 2007, 2009: 1051 - General Physics II: Oscillations, Waves, Electromagnetism.
is a calculus based introduction to oscillations, wave motion, physical optics and electromagnetism.
Prerequisites: Physics 1050 or 1020 (with a minimum grade of 65%) and Mathematics 1001. Mathematics 1001 may be taken concurrently.
Laboratories: Normally six laboratory sessions per semester, with each session lasting a maximum of three hours.


Fall 2007, 2009: 3220 - Classical Mechanics I.

covers kinematics and dynamics of a particle. Moving reference systems. Celestial mechanics. Systems of particles.
Prerequisites: Physics
2820 and Applied Mathematics/Pure Mathematics 3260. Applied Mathematics/Pure Mathematics 3260 may be taken concurrently.
Lectures: Three hours per week.


Winter 2001: 3230 - Classical Mechanics II. Rigid body motion. Lagrange's equations. Hamilton's equations. Vibrations. Special theory of relativity. Prerequisite(s): Physics 3220, Physics 3810 (or AM/PM 3202) and AM/PM 3260. Lectures: Three hours per week.

Winter 2002: 2056 - General Physics VI: Modern Physics. Special relativity, quanta of light, atomic structure and spectral lines, quantum structure of atoms and molecules, nuclei and elementary particles. Prerequisite(s): Mathematics 1001, Physics 1050 (or 1020 and 1021), and Physics 1054. Math 1001 and Physics 1054 may be taken concurrently. Lectures: Three hours per week. Laboratory: Three hours per week.

Winter 2002: 3300 - - Introduction to Physical Oceanography. The course deals with the physics of processes in the ocean, but provides an integrated view of the whole field of oceanography. The importance of physical processes to other aspects of oceanography is treated. Prerequisite(s): Physics 2053 and Mathematics 2000. Lectures: Three hours per week.

Winter 2003: 4205 - - Introduction to Fluid Dynamics (same as AM 4180). Basic observations, mass conservation, vorticity, stress, hydrostatics, rate of strain, momentum conservation (Navier-Stokes equation), simple viscous and inviscid flows, Reynolds number, boundary layers, Bernoulli's and Kelvin's theorems, potential flows, water waves, thermodynamics.. Prerequisite(s): Physics 3230 and either Physics 3821 or AM 4160.. Lectures: Three hours per week.

Fall 2003, 2004: 3821 - - Mathematical Physics III.   Further topics on the partial differential equations of mathematical physics and boundary value problems.
Prerequisite(s): Physics 3820.
Lectures: Three hours per week.

Fall 2003: 6323 - - Stability Theory.    Kelvin-Helmholtz and Rayleigh-Taylor instabilities, centrifugal instability, stability on f- and beta- planes. Effects of viscosity: Orr-Sommerfeld equation. Thermal instability, stability of stratified fluids, baroclinic instability, transition to turbulence.

Here are a few sample pages of Lecture notes "Stability Theory" (complete notes 112pp)

Winter 2013, 2012: P4300 (and parallel graduate course P6310) - -Advanced Physical Oceanography.  Fundamental properties of seawater and techniques of oceanographic measurement. The dynamical equations of oceanography are derived and solutions explored by comparison with oceanic observations. Properties of waves in rotating and non- rotating fluids. Linear and non-linear wave theory are developed.
Prerequisites: Physics 3300 and 3820, or Engineering 7033, or the permission of the instructor.
Lectures: Three hours per week.

Fall 2005: 6321 - -Coastal Oceanography.   Coastal circulation: observations and theory; coastal trapped waves; wind-forced response;  uniform density models; effect of density stratification
Prerequisites:  permission of the instructor.
Lectures: Three hours per week.

Labs:

P3900 - Vortex dipoles by PIV This is a new lab experiment in Physics 3900. The lab is based on modern computerized method of measurements of the fluid flow. Geophysically important structure: vortex dipole is studied in this lab. P3900 - Vortex dipoles by PIV (PDF file)

P3920 - Vortex dipoles II: Electromagnetic method This is a new lab experiment in Physics 3920. 

P2053 - Vortex streets This is a new lab experiment in Physics 2053. This laboratory experiment is designed to study regular arrays of vortices occurring behind an object in a stream of fluid. This phenomenon is observed in industrial flows, flows in the ocean and in the atmosphere. We consider the flow behind a circular cylinder. In the second part of the experiment the effect of the body on the fluid is imitated by using an appropriate force field when there is no real body present in the fluid. The force field (virtual body) is created by a permanent magnet located above the surface of water in combination with electric current applied in the horizontal direction. 

 


 


This site is maintained by: Yakov Afanasyev.
Last updated: November, 2011.

 


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