Turbulence and Complex Systems

Group Members

Name	Research Interests	Contact Information
David Newman	Dynamics and Control of SOC Systems (Sandpiles, Power Transmission, Communications, Traffic, Plasmas) Basic Plasma and Fluid Turbulence The Interaction Between Sheared Flows and Turbulence Modeling Transitions in Plasma Transport Dynamics of Atomistic Flows in Carbon Nanotubes Development of Higher Order Characteristic Measures of Dynamical Systems	Phone: (907) 474-7858 Fax: (907) 474-6130 Address University of Alaska-Fairbanks Physics Department P.O. Box 755920 Fairbanks, AK 99775-5920 USA Office Rm.: 112 Natural Science Facility E-mail: ffden@uaf.edu
Renate Wackerbauer	Complex temporal and spatiotemporal dynamics Modeling of biological systems          neuron dynamics          coupled oscillators          circadian rhythms          population dynamics Stochastic dynamical systems         Influence of noise/perturbations on nonlinear dynamical systems Nonlinear time series analysis	Phone: (907) 474-6108 Fax: (907) 474-6130 Address University of Alaska-Fairbanks Physics Department P.O. Box 755920 Fairbanks, AK 99775-5920 USA Office Rm.: 106 Natural Science Facility E-mail: ffraw1@uaf.edu
Graduate Students
Debasmita Samaddar	Turbulence modeling and the Interaction Between Sheared Flows and Turbulence	Phone: (907) 474-1938 Fax: (907) 474-6130 Address University of Alaska-Fairbanks Physics Department P.O. Box 755920 Fairbanks, AK 99775-5920 USA Office Rm.: 111 Natural Science Facility E-mail: ftds1@uaf.edu
Oralee Nudson	Agent Based Modeling of Complex Infrastructures
Seth Underwood	Dynamics of Flows in Nanotubes
Brian Wilson
Willis Ferenbaugh	Characteristic Measures of Dynamical Systems	Phone: (907) 474-1938 Fax: (907) 474-6130 Address University of Alaska-Fairbanks Physics Department P.O. Box 755920 Fairbanks, AK 99775-5920 USA Office Rm.: 111 Natural Science Facility E-mail: chowdery@yahoo.com
Graduated Aug. 2004 and relocated to a land down under Ryan Woodard	Dynamics of SOC Systems	Phone: Fax: Address University of Alaska-Fairbanks Physics Department PO Box 755920 Fairbanks, AK 99775-5920 USA Office Rm.: 111 Natural Science Facility E-mail: ryan@timehaven.org
Jon Klaas	Synchronization in Dynamical Systems (ie Biological systems)	Phone: (907) 474-1986 Fax: (907) 474-6130 Address University of Alaska-Fairbanks Physics Department PO Box 755920 Fairbanks, AK 99775-5920 USA Office Rm.: 105 Natural Science Facility E-mail: fsjpk@uaf.edu
Safia Rawoot	Transient Chaos in Multiple Topologies	Phone: (907) 474-1986 Fax: (907) 474-6130 Address University of Alaska-Fairbanks Physics Department PO Box 755920 Fairbanks, AK 99775-5920 USA Office Rm.: 105 Natural Science Facility E-mail: fssgr@uaf.edu
Current or recent Undergraduate Students
Cheradan Fikstad	Power Systems Network
Now at Dartmouth (Grad. School in Physics) John Broussard	Dynamics of transport models with noise	E-mail: fsjcb1@uaf.edu
Now at Univ. of Illinois (Grad. School in Physics) Keiko Ino	SOC and diffusion	E-mail: keikoroppi@hotmail.com
Now at Dartmouth (Grad. School in Physics) Sumire Kobayashi	Interaction between chaotic species	E-mail:

Visitors/Collaborators

Former Students

Projects and Areas of Interest (more coming)

1) Dynamics and Control of SOC Systems (Sandpiles, Power Transmission, Communications, Traffic, Plasmas)

Motivated by the complicated dynamics observed in simulations and experiments of gradient driven turbulent transport, a simple paradigmatic transport model based on the ideas of self organized criticality (SOC) has been developed and investigated . In many cases a strong coupling exists between the turbulence and bulk flows in the system. If the bulk flows are uniform the turbulence imbedded in the flow is simply advected and the dynamics are usually not changed. Often however, such flows are spatially dependent (sheared) and therefore can have an impact on the dynamics of the system. SOC systems have been the focus of much investigation recently due to the broad relevance of many of the characteristics of these systems. For example, 1/f noise is a ubiquitous feature in many diverse physical systems from starlight flicker through river flows to stock market data. Additionally many of these systems (and others) exhibit a remarkable spatial and temporal self-similar structure. The physical and dynamical self-similarity that is exhibited by these systems is very robust to perturbations and is not necessarily close to any "linearly marginal" state such as the angle of repose for a sandpile. It is this self-similarity and non linear self organization that leads to the term "Self-Organized Criticality". In many systems (magnetically confined plasmas for example) the transport of constituents down their ambient gradient is thought to be dominated by turbulent transport. That is a turbulent relaxation of the gradient. The turbulence itself is often driven by the free-energy in the gradient . It is this combination of turbulent relaxation removing the source of free energy thereby turning off the turbulence which then allows the gradient to build back up which allows the development of robust (albeit fluctuating) profiles. The dynamics of such systems can be computationally investigated with a cellular automata model of a running sand pile. This model allows us to investigate the major dynamical scales and the effect of an applied sheared flow on these dominant scales. In addition to allowing the paradigmatic investigation of turbulent transport, the introduction of sheared flow (wind) and the determination of transport coefficients in sandpiles, both of which naturally arise in the context of magnetically confined plasmas, act as a novel and important extension to the chaotic dynamics of SOC systems.

Recent papers in this area (in PDF format)

Power systems (HICSS2001 Data analysis paper 1 , HICSS2001 Modeling paper 1 , HICSS2001 Modeling paper 2 , HICSS2002 modeling paper 1 , HICSS2002 modeling paper 2 )

Communications systems ( HICSS2002 Modeling paper 1)

Basic SOC systems

Plasmas

2) The Interaction Between Sheared Flows and Turbulence

3) Basic Plasma and Fluid Turbulence

Investigations of the basic dynamics of the turbulent systems can shed light on both interesting nonlinear dynamics and real systems.

4) Modeling Transitions in Plasma Transport

Transitions to enhanced confinement regimes are very important for the success of the fusion energy program.

5) Dynamics of Atomistic Flows in Carbon Nanotubes

In nature the interaction between fluid flows and surfaces and the resultant transport due to the flows is both ubiquitous and of fundamental importance. One of the flow regimes of particular interest is that in which the fluid transitions to a turbulent flow. In this case, the transport characteristics and flow dynamics change dramatically. In addition to an enormous amount of attention given to these systems, much progress has been made in recent years on modeling and understanding the dynamics of these continuous fluid flows (CFD) using the Navier-Stokes equations. However, with the ever-increasing interest in smaller size devices (for example, in MicroElectroMechanicalSystems - MEMS applications) an interesting new regime is encountered. This is the regime in which the distance between surfaces becomes comparable to the atomic or molecular sizes of the flowing material. While the highly "viscous" flow through irregular microporous materials has been extensively studied the basic underlying physics of the "fluid" dynamics of flows through "smooth" regular structures on this scale have yet to be characterized. In particular, the demonstration and characterization of transitions in flows on these scales will have a profound impact on the development of the new blossoming capabilities in building micro and nano scale devices and structured materials.

A relevant yet simple realization of such a flow is that given by atoms flowing through carbon nanotubes. Typically, in nano scale systems, the effective viscosity is expected to be high unless, perhaps, the flow "channel" is very regular and smooth such as that found inside a carbon nanotube, for example. Investigation of these "atomistic" flows is of interest for the obvious reason that one must understand how material flows in these nanotubes if one wishes to use them. More importantly the demonstration of new flow dynamics with transitions within the tube could lead to altogether new uses. In addition, basic understanding of flows on these scales may be of relevance in the extreme boundary layer of continuous (Navier-Stokes) flows and may help in the design of special coatings, for example, to decrease (or increase) drag. It should be stressed that the novel aspect of this is not simply the nanoscales in the system, but rather the interaction between the atomistic flow and the very regular surface created by the nanotubes etc. This research project, which is on the cutting edge of the burgeoning field of nanotechnology, can at the same time make fundamental contributions to the underlying basic physics.

 

6) The Effect of Noise on Propagation in Reaction-Diffusion Equations

7) Development of Higher Order Characteristic Measures of Dynamical Systems

Support from DOE under grants DE-FG03-99ER54551 and DE-FG03-00ER54599 (a young investigator award) and NSF under grant ECS-0085647 are gratefully acknowledged

Professional links of interest

• The Physics Department at UAF
• The Geophysical Institute
• sci.nonlinear FAQ (Sept 96)
• The American Physical Society
• Oak Ridge National Laboratory

Other links of interest

• View from Natural Sciences Building on the UAF campus
• Incredible Mt. Etna Smoke rings
• Link to Auroral Forecast at the GI
• TTF2001
• Dynamics of Complex Systems

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PDF file format

Many of the papers found on these pages are in pdf format. To find out more about pdf viewing or to get a free viewer for pdf documents see Adobes Acrobat Reader (for Macintosh(R), IBM AIX, Windows(R), Sun(TM) SPARC(R), HP/UX(TM), Silicon Graphics(R) and others) or Xpdf (for x86 - Linux 2.0 ELF , PowerPC - AIX 4.1 , SPARC - SunOS 4.1.3 , MIPS, Ultrix 4.4 , Alpha - OSF/1 3.2 , HP-PA, HP-UX 9.05 , and others).

Hits since 3 June 2002

Last changed on 28 January, 2008 .

This page is maintained by David Newman