  Fluid transport networks are important in many natural settings and
engineering applications, from animal cardiovascular and respiratory systems to
plant vasculature to plumbing networks and chemical plants. Understanding how
network topology, connectivity, internal boundaries and other geometrical
aspects affect the global flow state is a challenging problem that depends on
complex fluid properties characterized by different length and time scales. The
study of flow in micro-scale networks focuses on low Reynolds numbers where
small volumes of fluids move at slow speeds. The flow physics at these scales
is governed by the Stokes equation, which is linear. This linearity property
allows for relatively simple theoretical and computational solutions that
greatly aid in the understanding, modeling and designing of micro-scale
networks.
  At larger scales and faster flow rates, macrofluidic networks are also
important but the flow physics is quite different. The underlying Navier-Stokes
equation is nonlinear, theoretical results are few, simulations are
challenging, and the mapping between geometry and desired flow objectives are
all much more complex. The phenomenology for such high-Reynolds-number or
inertially-dominated flows is well documented and well-studied: Flows are
retarded in thin boundary layers near solid surfaces; such flows are sensitive
to geometry and tend to separate from surfaces; and vortices, wakes, jets and
unsteadiness abound. The counter-intuitive nature of inertial flows is
exemplified by the breakdown of reversibility. This dissertation explores two
general ways of how rectified flows emerge in macrofluidic networks as a
consequence of irreversibility and unsteady effects: When branches or channels
of a network have asymmetric internal geometry and the second when a network
contains loops.
