CASPO Seminar: Dr. Rich Rotunno, "Anatomy of the Lee-Side Hydraulic Jump"

04/03/2018 - 3:30pm to 4:30pm
330 Spiess Hall
Event Description: 

Dr. Rich Rotunno


AbstractLaboratory observations of the lee-side hydraulic jump indicate it
consists of a statistically stationary turbulent motion in an overturning
wave. From the point of view of the shallow-water equations (SWE), the
hydraulic jump is a discontinuity in fluid-layer depth and velocity at
which kinetic energy is dissipated.  To provide a deeper understanding of
the lee-side hydraulic jump, three-dimensional numerical solutions of the
Navier-Stokes Equations (NSE) are carried out alongside SWE solutions for
nearly identical physical initial-value problems. Starting from a
constant-height layer flowing over a two-dimensional obstacle at constant
speed, it is demonstrated that the SWE solutions form a lee-side
discontinuity owing to the collision of upstream-moving  characteristic
curves launched from the obstacle. Consistent with the SWE solution, the
NSE solution indicates the lee-side hydraulic jump begins as a steepening
of the initially horizontal density interface. Subsequently, the NSE
solution indicates overturning of the density interface and a  transition
to turbulence. Analysis of the initial-value problem in these solutions
shows that the tendency to form either the lee-side height/velocity
discontinuity in the SWE, or the overturning density interface in the
exact NSE, is a feature of the inviscid, nonturbulent fluid dynamics.
Dissipative turbulent processes associated with the lee-side hydraulic
jump are a consequence of the inviscid fluid dynamics that initiate and
maintain the locally unstable conditions.

For more information on this event, contact: 
Art Miller
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