Events Calendar

Astani Civil and Environmental Engineering Ph.D. Seminar

Speaker: Luis Montoya and Seyedpouyan Hosseinialiabad, Astani CEE Graduate Students

Talk Title: Understanding Properties of Extreme Ocean Wave Runup and Analysis and Control of Signalized Arterial Networks

Abstract: In recent history sneaker waves or king waves in Australia, also referred in this study as extreme infragravity EIG waves, have been responsible for killing many people throughout the world. Particularly so on the coast of Oregon, where more than 21 people have died since the year 1990 due to this phenomenon. These extreme runup events may also result in coastal flooding, beach erosion, damage to coastal structures and damage to marine vessels. In this study, the main objective is to better understand EIG waves and EIG wave runup during storms. It is revealed that the input spectrum frequency resolution plays an important role when studying IG waves and runup. Also, it is shown that there is an ideal frequency resolution which can make the modeling part more accurate and efficient by capturing most of the low frequency energy transfers during the nonlinear wave interactions. It is established that runup predictions from numerical simulations that use 10 frequencies in the input energy spectrum are not the same from those that use 100 frequencies because of nonlinearity. It is established that extreme runup is therefore affected by frequency resolution and convergence can be achieved using the fine resolution. For high energy wave conditions, with beaches that have IG-dominated runup, in order to get numerically convergent predictions of 0.0001-0.00005 Hz is needed. This is more than 100 times smaller than what is typically used in these Boussinesq coastal phase-resolving models.


Talk Title: Analysis and Control of Signalized Arterial Networks

In this study, we first focus on queue length analysis of urban traffic networks. We consider traffic flow dynamics for a network of signalized intersections, where the outflow from every link is constrained to be equal to a given capacity function if the queue length is positive, and equal to the minimum of cumulative inflow and capacity function otherwise. In spite of the resulting dynamics being discontinuous, recent work has proved existence and uniqueness of the resulting queue length trajectory if the inter-link travel times are strictly bounded away from zero. We provide an alternate framework to obtain queue length trajectories by direct simulation of delay differential equations, where link outflows are obtained from the provably unique solution to a linear program. Existence and uniqueness of the solution to the proposed model for traffic flow dynamics is established for piecewise constant external inflow and capacity functions. Additionally, if the external inflow and capacity functions are periodic and satisfy a stability condition, then there exists a globally attractive periodic orbit. We provide an iterative procedure to compute this periodic orbit. A periodic trajectory is iteratively updated for every link based on updates to a specific time instant when its queue length transitions from being zero to being positive. The resulting iterates are shown to converge uniformly monotonically to the desired periodic orbit. Illustrative simulation results are presented. In the second part of this study, we focus on control techniques for signalized arterial networks. We study the throughput of arterial network under specific type of adaptive controller, namely Proportionally Fair, and traditional Fixed-time controllers. This comparison is done both in terms of theoretical upper bounds and the empirical values calculated from microscopic traffic simulations.

Location: Von Kleinsmid Center For International & Public Affairs (VKC) - 150

Audiences: Everyone Is Invited

Contact: Evangeline Reyes