(39e) Thinking Outside Our Box: On Being a Fluid Mechanical “Missionary”

This abstract is meant to be provocative.

The fluid mechanics community has seen incredible advances
in the last century:  a deep,
physical understanding of a wide variety of fluid phenomena; the mathematical
formulation of fluid mechanical problems (and particularly the value of non-dimensionalization); asymptotic analysis for accurate
approximations (and the physical intuition that arises from such approximations);
and powerful computers and algorithms that enable direct numerical simulations
that would have been inconceivable a few decades ago.

That said, I fear that we in the
fluid mechanics community have evolved so far, and in a direction that many of
our colleagues in Chemical Engineering and other disciplines have not, that the
wealth of expertise and intuition we have developed does not have the impact on
the broader community that it should.  In addition to framing the broader
discussion in this session about "New Directions" for fluid mechanics, I will
briefly discuss some work we did that was part research, part academic
"outreach".  A large community has
been working to develop bio-sensors; some come from ChE,
but many are in Chemistry, Mechanical or Electrical Engineering, Physics,
Materials, Biology, Bioengineering, in other disciplines and in industry.  With few exceptions, researchers in
these disciplines are not trained to think about the convective, diffusive, and
reactive transport of solute in flowing solutions, and yet these transport issues
are central to the operation, performance, and interpretation of these
sensors.  A controversy had emerged
regarding the practicality (or even possibility) of nanowires as sensors for
extremely dilute (e.g. femtomolar) solutions.  The question was a quantitative one,
albeit with a large parameter space, and yet the debate was largely
qualitative.   Published COMSOL
computations for one system would be used to justify assertions about a
completely different system, and so on.

            We
constructed a simple model system that captured the key features of many of
these sensor systems, and fleshed out the variety of behaviors and parameter
regimes that arise.  We then set
ourselves the challenge of trying to develop and convey a fundamental
understanding of these transport processes without
requiring partial differential equations, much less matched asymptotic
equations.  Our central goal was to
try to help a wide variety of researchers, with an equally wide variety of
backgrounds, to learn how to think about transport in these systems.

            I
will argue that our field would benefit from more of this kind of "missionary"
work – the need is out there, and yet the gap between how we understand
solve problems, and how other fields are trained to do so, is severe enough
that necessary expertise does not find its way to the communities it could
benefit.  The more we interact with
other fields and disciplines, the more impact we will have.  Doing so will additionally expose us as
researchers to interesting challenges faced by other disciplines.