# ME Seminars on "Modeling “Morning Glory:” how do we develop simple analytical models for internal bores?" & "Microfabrication of Bio-Inspired Adhesive Systems"

## Date:

Monday, April 22, 2013 - 4:00pm to 5:00pm

**ESB 1001**

## Speaker:

Zachary Borden, Sathya S. Chary
Modeling “Morning Glory:” how do we develop simple analytical models for internal bores?
Zachary Borden
Internal bores, or hydraulic jumps, arise in many atmospheric and oceanographic phenomena. The most well known atmospheric internal bore is the “Morning Glory” cloud off the northwestern coast of Australia, but atmospheric bores occur planet wide and are important because they can worsen already sever weather. In marine environments, internal bores can be caused by the breaking of internal waves or by the interaction of stratified flow with complex topography. It is thought that marine bores play an important role in the global energy cascade and in the transport of sediment.
At its most basic, a model of an internal bore needs to predict its speed of propagation given the bore's size. Historically, analytical models use an integral analysis to relate these two quantities. A control volume is constructed around the front of the bore, and then mass and momentum are conserved across it. For one-layer bores (i.e. bores propagating on the surface of water), these two equations are sufficient to obtain a solution. But, for two-layer internal bores, an additional equation is needed.
In this presentation, I will discuss the history of this third equation, usually an assumption relating the down- and upstream energy fluxes, before developing my own third equation based on observations from two- and three-dimensional direct numerical simulations of internal bores. Finally, I will discuss our most recent work in which we remove the need for a third equation entirely by reframing the conservation of momentum in terms of vorticity.
---Biography---
Zac Borden graduated in 2008 from Franklin W. Olin College of Engineering with a degree in Mechanical Engineering. Now, he is a Ph.D student in his fifth year at UCSB, working in Eckart Meiburg's computational fluid dynamics lab. Zac's research focuses primarily on using the data and insights gathered from highly resolved numerical simulations of large-scale geophysical flows to develop simple analytical models that describe their behavior. But he also spent one year of his studies in Perth, Australia working on the accurate simulation of particle erosion and deposition. After graduating this spring, he will join the ExxonMobil Upstream Research Company as a computational scientist.