Christine Gilbert, an assistant professor in the Kevin T. Crofton Department of Aerospace and Ocean Engineering, has been awarded a National Science Foundation Faculty Early Career Development (CAREER) award.

Taking inspiration from nature, she will study the interaction of a highly flexible plate near a free surface, more specifically, how shape reconfiguration affects the flow field and results in drag reduction on the body.

With the $500,000 CAREER grant, Gilbert will take inspiration from structures that are flexible in nature and perform laboratory-scale experiments on thin plates made of fiber composites and polymers. 

“While there have been studies on the phenomenon of drag reduction in a single fluid, such as a submarine deep below the surface, this particular project will focus on the air-water interface, or the free surface,” said Gilbert. “By better understanding this fundamental science, we have the potential to discover new, unique propulsion methods that are more energy efficient and adaptive to different environments.” 

With her research team, Gilbert will study how the flow field changes as a result of shape reconfiguration, including how the drag on the body can be reduced. The shape reconfiguration will be done both passively and actively. The active reconfiguration will be achieved by controlling the material properties of the plate and is similar to the flexing of muscles. While this project is primarily an experimental study, there will be plans to use theoretical formulations and numerical simulations to help design the experiment and to make predictions on the results of the experiment. Existing theoretical formulations will be modified and extended for this purpose. 

Experiments will be conducted in the department’s Hydroelasticity Laboratory and the towing tank facility. The towing tank facility is currently being upgraded with a new towing carriage and vertical planar motion mechanism. The study will start in the Hydroelasticity Laboratory by oscillating a flexing plate vertically in the slamming tank. The team will gain a better understanding of the flow characteristics and how the structure needs to adapt to provide the least amount of resistance to the flow. 

Moving to the towing tank, they will add forward propelling motion to the vertical oscillating motion to document how the motion and structure of the plate affects the surrounding flow and in turn, reduces drag.

In the Hydroelasticity Laboratory, Gilbert plans to oscillate a flexible v-shaped plate vertically in the slamming tank, to better understand the flow characteristics.
In the Hydroelasticity Laboratory, Gilbert plans to oscillate a flexible v-shaped plate vertically in the slamming tank, to better understand the flow characteristics. Courtesy of Christine Gilbert.

Particle image velocimetry (PIV) measurements will yield velocities and pressures, and stereoscopic digital image correlation (S-DIC) and high-speed photography will be used to measure plate deflections at the water-structure interface. Pressure and force sensors on the plate will measure fluid loads on the structure.  Experimental results will be compared with numerical simulations and theoretical formulations.

The results of Gilbert’s research have the potential to improve propulsion methods by understanding how to reduce drag and improve energy efficiency on undulatory propulsors and vessels.

An educational and outreach component of the project will impact the education of middle and high school aged students in the New River Valley, through collaboration with the Center for the Enhancement of Engineering Diversity at Virginia Tech. In addition, Gilbert will participate in TechGirls, an international summer exchange program designed to empower and inspire young girls from the Middle East, North Africa, and Central Asia to pursue careers in science and technology.

Gilbert was previously awarded the Office of Naval Research’s Young Investigator Program Award in 2015, and was awarded a Defense University Research Instrumentation Program grant in 2018 to modernize the 60-year-old towing tank facility in Norris Hall.

— Written By Jama Green