Category Archives: Civil and Construction Engineering

Tsunami Surfing and the Giant Snot

Sam Harry’s research is filled with bizarre scientific instruments and massive contraptions in an effort to bring large natural events into the laboratory setting. 

Sam Harry, second year PhD candidate in Civil Engineering

“There’s only a couple like it in the world, so it’s pretty unique”. Unique may be an understatement when describing what may be the largest centrifuge in North America. A centrifuge is a machine with a rapidly rotating container that can spin at unfathomable speeds and in doing so applies centrifugal force (sort of like gravitational force) to whatever is inside. This massive scientific instrument– with a diameter of roughly 18 feet– was centerpiece to Sam’s Master’s work studying how tsunamis affect boulder transport, and the project drew him in to continue studying the impact of tsunamis on rivers for his PhD. 

But before we jump ahead, let’s talk about what a giant centrifuge has to do with tsunamis. Scientists studying tsunamis are faced with the challenge of scale; laboratory simulations of tsunamis in traditional water-wave-tank facilities are often difficult and inaccurate because of the sheer size and power of real tsunamis. By conducting experiments within the centrifuge, Sam and his research group were able to control body force within the centrifuge environment and thus reduce the mismatch in fluid flow conditions between the simulated experiment and real-life tsunamis. 

When tsunamis occur they cause significant damage to coastal infrastructure and the surrounding natural environment. Tsunamis hit the coast with a force that can move large boulders– so large, in fact, that they aren’t moved any other way. Researchers can actually date back to when a boulder moved by analysing the surrounding sediments, and thus, can back calculate how long ago that particular tsunami hit. However, studying the movement of massive boulders, like tsunamis, is not easily carried out in the lab. So, Sam used a wave maker within, of course, the massive centrifuge to study the movement of boulders when they are hit with some big waves. 

Sam’s work space. The Green dye added to the water within the glass tank is what gives this tank it’s name: The Giant Snot

As Sam was completing his Master’s an opportunity opened up for him to continue the work that he loves through a PhD program in civil engineering with OSU’s wave lab. Now Sam conducts his research using the “glass tank”, which, as the name alludes to, is a glass tank roughly the size of a commercial kitty pool that is used to contain the water and artificial waves the lab generates for their research. There are actually three glass tanks of varying sizes. The largest tank, which is larger than a football field, is used for more “practical applications”. Sam gives us the example of a recent study in which researchers built artificial sand dunes inside of the tank, let vegetation establish, and then hit the dunes with waves to study how tsunamis impact that environment. (Legend has it that the largest tank was actually surfed in by one of the researchers!)

Sam’s smaller glass tank, though, is really meant for making precision measurements to better study waves. He uses lasers to measure flow velocity and depth of water to build mathematically difficult, complex models. Essentially, his models are intended to be the benchmarks for numerical simulations. Sam, now into his second year of his PhD, will be using these models in his research to study the interaction between tsunamis and rivers, with the goal of understanding the movement and impact of tsunamis as they propagate upstream.

To learn more about tsunamis, boulders, rivers, and all of the interesting methods Sam’s lab uses to study waves, tune into KBVR 88.7 FM on Sunday, November 3rd at 7pm or live stream the show at http://www.orangemedianetwork.com/kbvr_fm/. If you can’t join us live, download the episode from the “Inspiration Dissemination” podcast on iTunes!

Improving hurricane prediction models using GPS data

GPS satellites orbiting the Earth

Exploiting a flaw in the system

GPS was originally designed for positioning, navigation, and timing (PNT) applications which measures the transmitted time of the radio signals from a satellite in the space to a receiver on the ground. But this story is not about improving GPS accuracy in navigation applications, rather it is a clever use of the GPS signal delay to collect data for monitoring the atmosphere for use in weather event predictions.

The transmitted GPS signal contains not only the range information, which is the primary factor of interest, but also error sources, such as atmospheric delay including tropospheric delay. The delay in GPS signals reaching Earth-based receivers due to the presence of water vapor is nearly proportional to the quantity of water vapor integrated along the signal path.

GPS is capable of seamless monitoring of the moisture in the atmosphere with high temporal and spatial resolution. Excellent GPS data availability enables unique opportunities for data analysis and experimental studies in GPS-meteorology.

This week’s guest, Hoda Tahami, is a third year PhD student in Dr. Jihye Park’s geomatics research group in the Department of Civil and Construction Engineering. Using geomatics – the science of gathering, storing, processing, and delivering spatially referenced information – Hoda is working to improve weather models for hurricane prediction.

GPS Meteorology: Estimating vertically integrated atmospheric water vapor, or perceptible water, from Global Positioning System (GPS) radio signals collected by a regional network of ground-based geodetic GPS receiver.

Using GPS signal data for hurricane prediction

Data from Hurricane Matthew that hit Florida in 2016 has been used to explore the idea of using GPS data to predict the path and intensity of hurricanes. “I found a clear correlation between [signal delay] and other atmospheric variables, like temperature, precipitation, and water vapor,” says Hoda. This information can be used for weather models, which rely on quality observational data. Weather models are computer programs that apply physics to observations to make predictions. The set of observations forming the starting point for the model simulation are called the initial conditions. Hoda hopes that this new set of data can be used as an initial condition for existing atmospheric models.

This new set of GPS-based data provides an increase in temporal and spatial resolution. While many satellite data sources provided data every few hours or even just once or twice a day, Hoda explains, “The time scale in my data is in seconds. We average it to five minutes, then use it to make one to twenty-four hour predictions.” This new set of data can be used to complement existing data sets – each with their own caveats – used by agencies like the National Hurricane Service, National Oceanic and Atmospheric Administration (NOAA), and the National Weather Service.

More information about the proposed model can be found at: https://www.ion.org/publications/abstract.cfm?articleID=15074

Hoda Tahami with her poster at the Graduate Research Showcase at Oregon State University

Finding a love for geospatial research

Hoda began her career in civil engineering with a bachelor’s degree at K. N. Toosi University of Technology in Tehran, Iran. This was Hoda’s first experience with geospatial data and geographic information systems (GIS), which piqued her interest and led her to pursue a Master’s degree specializing in GIS. Due to the state-of-the-art geospatial research resources available, Hoda chose to pursue her doctorate degree at Oregon State.

Join us on Sunday, May 5 at 7 PM on KBVR Corvallis 88.7 FM or stream live to learn more about Hoda’s geospatial research and journey to graduate school.