The Language of Water and Our Greatest Translators
This post is in memory of my advisor, Nirnimesh Kumar, who had a passion for understanding the very fundamentals of fluid motion and an unfathomable aptitude for solving any problem with numerical modeling.
The motion of water is a universal language. Its calls can be heard in the churn of 12,000 cubic feet of water per second rushing down the Mississippi River and the crashing of 60-foot breaking waves in the open waters of the Pacific Ocean. Its stories shape the land we rely on, driving floods that can fertilize agricultural land with nutrient-rich sediments and moving heat from the equator toward the poles to control the climate via ocean currents. We impose our grammar rules so it can fit our needs by building monolithic concrete dams to halt its passage to the ocean, drawing it from rivers to facilities where it is treated and sent to homes in pressurized pipes, and armoring shorelines to alleviate erosion by waves along our coasts. As if changing the blueprint of water motion was not enough, we attempt to predict its next chapter by forecasting the height of storm surge to determine who to evacuate during a hurricane or the likelihood of hazardous rip currents at beaches to know when to warn swimmers.
Throughout hundreds of years of curiosity and brilliant science discoveries, we have learned how to describe water motion in equations that range from simply calculating the flow rate of rivers based on the area and velocity, to representing complex fluid motion in almost any environment. The equations are the translators for our understanding of the language of fluid motion. They lay out a pathway from our physical reality to numerical models, a method to represent and predict complex fluid behavior using the processing capabilities of computers.
For example, numerical models can help predict the impact of a tsunami on coastal communities. Imagine laying out a checkerboard from the beach to as far as you can see offshore. You know the layout of the checkerboard at the beginning of a game, just as you can input the properties of an incoming tsunami at the farthest offshore edge. You use strategy to decide on your next move forward with each turn, just as models use equations to estimate how the wave transforms as it moves onshore with each time step. At the culmination of the game, when you have overtaken your opponent, you know the final result and the path that got you there, just as model results will reflect the distance onshore the wave traveled and time it took to arrive. A numerical model can tell us how the tsunami impact varies based on the community’s elevation above sea level and even how the exact layout of the infrastructure could alter destruction by the tsunami event.
Numerical modeling provides us with high-resolution insight into fluid motion, supplying us with far more information than we can collect in the field, such as tracking the route of individual water particles from a river mouth out into the open ocean. Model setups that are representative of natural environments can be compared against measurements to help us identify the legitimacy of model equations. From predicting the increase of wave-driven erosion along the Alaskan coast when the land is no longer covered in ice to understanding the implications of sea-level rise on coastal habitats, modeling gives us insight into the language of water motion, allowing us to understand its complexity and intricacies. As we uncover its stories, modeling can help us continue to comprehend the water’s constantly evolving messages and keep the conversation flowing.
Christine Baker, a graduate student in Civil and Environmental Engineering at the University of Washington, studies the movement of water by currents that are driven by breaking waves along the coast, specifically rip currents, which are hazardous for recreational swimmers. Using large-scale laboratory experiments, she seeks to understand when and how sand, pollutants, larvae, and unsuspecting swimmers move from the region where waves break to the open ocean.