Michael P. Hallberg

Research Interests

-jet stability, global modes, absolute instability, open-loop control, computational fluid dynamics, cosmology

Papers

“Open-loop control of fully nonlinear self-excited oscillations.” In Physics of Fluids.

“Suppression of global modes in low-density axisymmetric jets using coflow.”  In Physics of Fluids.                 

“On the universality of global modes in low-density axisymmetric jets.” In Journal of Fluid Mech.

“Stability and control of very low density axisymmetric jets.”  AIAA-2006-3704 from the 3rd AIAA Flow Control Conference.

Research

I am currently a Ph.D. candidate in mechanical engineering at the University of Minnesota in the thermal science/heat transfer (THT) division. 

The lab I work in is the Shear Flow Control Lab under the direction of Prof. P.J. Strykowski.

I am funded under a grant from the National Science Foundation with the goal of simulating a plasma jet using room temperature gasses. Plasma jets are created by sending a gas through a nozzle in the presence of a high energy spark that heats the gas to very high temperatures (>10000K). Plasma jets are generally used to coat surfaces (such as turbine blades) with very hard materials (such as ceramic) in a process called plasma spraying.  The extreme environment of the plasma creates a jet that mixes very rapidly while at the same time being extremely difficult to interrogate.  If the plasma can be simulated using gases at room temperature, several diagnostic techniques can be used to shed light on the underlying fluid mechanics in hopes of reducing mixing - thereby creating a better plasma spray. 

The work thus far has been very successful on a fundamental level and has allowed us to shed light on instabilities inherent to low density flows (see papers above).  In short we have shown that certain features of the global mode in a low-density jet can be predicted very accurately using conditions at the exit of the jet.  Recent nonlinear theoretical work (from people such as J-M Chomaz, P. Huerre, B. Pier among others) based on wakes shows there exists a connection between the nonlinear evolution of the flow and the underlying linear stability.  This theory is well tested in the wake and seems to answer the age-old question of singing wires first investigated more than a century ago by V. Strouhal.  While not absolutely proven, my work provides circumstantial evidence that the same theoretical underpinnings apply to the low-density jet.


Michael Paul Hallberg
University of Minnesota
Mechanical Engineering
ME162
612-625-8058

Last modified: Wed September 6, 2006