OSE PhD Defense: Alexandra Muscalus
Title: Characterization of Low-Frequency Ship Wake along the Margins of Confined Channels and Connected Waterways
Date/time: Tuesday, November 29, 2022, 10:00am EST
Location: SEB 122
Virtual:  https://gatech.zoom.us/j/98768644195
Advisors: Dr. Kevin A. Haas (CEE) & Dr. Donald R. Webster (CEE)
Committee: Dr. Clark Alexander (SkIO), Dr. Annalisa Bracco (EAS), Dr. Marc Weissburg (BIOS) 

Maritime shipping is essential to the global economy, but the ship wake produced by large cargo ships in the coastal environment can cause erosion and threaten shoreline features. As large ships navigate confined channels near ports, they produce low-frequency (LF) wake that stems from a water surface depression bound to the ship. At the margins of the channel, LF wake creates a tsunami-like effect for several minutes as the ship passes. Afterwards, LF waves called “trailing waves” can persist in the channel for over 30 minutes. In this research, LF wake is characterized at the shipping channel margins and connected waterways using numerical modeling and field measurements from the Savannah River, Georgia. In the first study, the significance of LF wake to coastal erosion is assessed using power as a proxy for erosion potential. Results show that LF wake is far more powerful than tidal currents and wind waves and is the dominant driver of erosion. The second study examines the propagation of LF wake out of the shipping channel and into the “far-field” with field measurements in a waterway network connected to the river. It reveals that LF wake readily reaches far-field rivers and creeks, propagating over 10 km as a long wave. The power of far-field LF wake is similar to that of tidal currents but is reduced by waterway junctions and energy dissipation. In the third study, trailing waves, often assumed to be cross-channel seiches, are investigated with FUNWAVE-TVD modeling and field measurements. Modeled ship passages in a simple channel generate trailing waves that are found to be edge waves propagating on the channel margins. For passages modeled in a realistic channel, the wave field is more complex: trailing waves reflect off of shoreline protrusions and propagate in multiple directions, which is congruent with field observations. The model shows that this complex wave field too consists of edge waves. As a whole, this research provides a characterization of LF wake near shipping channel margins and nearby waterways that is supported with extensive field observations and can inform wake prediction, wake mitigation strategy, and future studies about the coastal impacts of LF wake.
Fran Lapolla (2022)