Aerospace and Mechanical Engineering
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AEM faculty spotlight:

Daniel Joseph

   At first glance, tornadoes and dust storms may just appear to be frightening, powerful aspects of nature. But to Daniel Joseph, a fluid mechanics professor in AEM, such phenomena are understandable through science at a very precise level. Joseph, an expert in flow – the characteristics of the motion associated with liquids and gases – says the science behind the movement of dust storms may lead to permanent remedies. Professor Joseph has organized an international group to study the flow characteristics of these types of natural disasters. Below, Professor Joseph talks about this endeavor and his new book on potential flows of viscous and viscoelastic fluids.

Joseph
Daniel Joseph

Tell me about the group you’ve assembled to deal with natural disasters like hurricanes or dust storms.
A topic which I’ve been active in recently is my effort to form an international collaboration on a topic which I call multi-phase turbulence. This encompasses dust storms, erosions, hurricanes, and tornados. We had a workshop on that subject in July in China with various experts working with us from the US, Australia, and China.  The idea of this is that in all these catastrophic geophysical flows like dust storms and tornados, the critical item is the suspension of the particles. That’s what produces the pollution, that’s what produces the danger to health and the environment. So our idea was to do controlled experiments in the regime of turbulence and determine the effect of loading different kinds of particles.
Could someone dissipate a dust storm?
It’s the usual story in research – we are looking toward understanding and of course the remedies may come later or simultaneously with understanding of the topic. There are understandings that could contribute a lot. I know those we’re collaborating with in China do a lot of work on vegetation in their wind tunnel tests, so remedies are definitely of interest. I was in Beijing and they had a dust storm; I woke up in the morning and there was dust all over everything and thick in the air. It hung there in a week, and came down when it rained. This storm came thousands of kilometers from Mongolia. We’ve found in the literature that when you pick up dust, you don’t pick it up uniformly from the ground, there are sources for the dust. If those sources could be remedied, then we could possibly have a good remedy.
What other research are you doing?
I have been working on the properties of polymer solutions mixed with silica nanoparticles. These mixtures give rise to exceptional mechanical behaviors which are dramatically different than what they would be if they had no silica particles. These silica polymer composite solutions were tested by taking bottles with solution and putting them in a refrigerator. We measured viscosity regularly, and the viscosity didn’t change. If there were no nanoparticles, you’d get a marked degradation of viscosity.   This solution which we created by interacting polymers with silica nanoparticles that resist oxidation. We don’t yet know if it’s stable against deformation, that’s what we’d like to test next. If it is, it may be an important new material with new properties.
Tell me a bit about your latest book and what you hope will change because of it.
Basically, the book takes a new direction in the field of fluid mechanics. Authors of textbooks say potential flows are only for inviscid fluids. Those people would regard the title of my book as an oxymoron. But we have established that there is indeed potential flow of viscous fluids and these flows are required to satisfy boundary conditions. We have showed how potential flows enter into the exact theory of the equations for viscous fluids and how purely irrotational theories faithful to physics may be constructed,
I hope that the book will change the face of teaching of every single course on fluid mechanics. In the case when viscosity acts, there are various ways it does act. It can get technical, but this essentially means that viscous stresses are important in potential flows even though they do not drive motions because the viscous dissipation is never zero.  The way I’ve presented the subject is to present the theory that potential flows are looked at how they enter solutions and how to construct approximations that have an important component that you wouldn’t get from the traditional way of doing the subject.

 


Last Modified: Tuesday, 09-Oct-2007 07:42:40 CDT -- this is in International Standard Date and Time Notation