Events Calendar

Astani CEE Dept. Seminar

Speaker: Dr. Philip L-F. Liu , Class of 1912 Professor in Engineering, School of Civil and Environmental Engineering, Cornell University

Talk Title: Some Recent Advancement in Tsunami Research

Abstract: Dr. Liu plans to give a brief progress report on two on-going research projects, related to coastal effects of tsunamis.

The first problem concerns the effects of coastal forest on wave propagation and dissipation. A mathematical model for wave propagation in a lattice-like array of vertical cylinders is developed, where the macro-scale variation of waves is derived from the dynamics in the micro-scale cells. Assuming infinitesimal waves, periodic lattice configuration and strong contrast between the lattice spacing and the typical wavelength, the perturbation theory of homogenization (multiple scales) is used to derive the effective equations governing the macro-scale wave dynamics. The constitutive coefficients are computed from the solution of micro-scale boundary value problem for a finite number of unit cells. Eddy viscosity in a unit cell is determined by balancing the time averaged rate of dissipation and the rate of work done by wave force on the forest at a finite number of macro stations. While the spirit is similar to RANS scheme, less computational effort is needed. Using one fitting parameter, the theory is used to simulate three existing experiments with encouraging results. Limitations of the present theory are also pointed out.

The second research topic aims to establish the correlations among bed shear stress, the near-bed velocity and the surface elevation of a leading tsunami wave form during the run-up and down-rush. To this end, a new shear plate device is designed and constructed, consists of a small shear plate attached to the housing via vertical supports that provide a restoring force. The plate is subject to fluid shear and pressure forces and these can be measured via the displacement of the plate and pressure tapings. The average shear stress on the plate can then be calculated. Experiments have been conducted using this device on a sloping ‘beach’ at Oregon State University’s Hinsdale Wave Research Laboratory in the Long Wave Flume and in a constant depth at Cornell’s DeFrees Laboratory in the Small Wave Flume. The laminar bed shear stress measurements under a solitary wave agree well with the theory and existing PIV data. Bed shear stress measurements for a breaking solitary wave on a slope are collected in the surf zone and swash zone. Temporal and spatial variations of bed shear stress are correlated to the near-bed velocity and water depth.


Biography: Dr. Liu earned his bachelor’s degree in civil engineering from National Taiwan University, his master’s degree in civil engineering from Massachusetts Institute of Technology (MIT), and his doctoral degree in hydrodynamics from MIT. Dr. Liu is the Director of the School of Civil and Environmental Engineering at Cornell University, where he has served as professor for his entire career. Dr. Liu has made major research contributions in developing water wave theories and modeling methodologies for tsunami dynamics. His research has yielded practical results including those obtained by his COMCOT (Cornell Multi-grid Coupled Tsunami) and COBRAS (Cornell Breaking Waves and Structures) models and from the field data from multiple post-tsunami field surveys, including Sri Lanka. Among his many awards, Dr. Liu received ASCE’s Walter L. Huber Civil Engineering Research Prize in 1978, ASCE’s John G. Moffatt-Frank E. Nichol Harbor and Coastal Engineering Award in 1997, and ASCE’s International Coastal Engineering Award in 2004. He also received a fellowship from the J.S. Guggenheim Foundation in 1980 and an Alexander von Humboldt Research Award in 2009. Dr. Liu was elected fellow of the American Geophysical Union in 2006 and is an elected ASCE distinguished member.

Host: Astani CEE Dept.

Location: Kaprielian Hall (KAP) - 209

Audiences: Everyone Is Invited

Contact: Cassie Cremeans