Student: Christopher Ruhl

Project: Characterization of Tunable Active Grid Generated Turbulence in a Water Tunnel Facility

View: Research Poster (PDF)| Presentation (YouTube)

Department: Mechanical Engineering and Mechanics

Advisor: Arindam Banerjee


In the past quarter-century, extensive research of wind-tunnel active grid turbulence generating devices has allowed researchers to fine-tune turbulent flow in experimental settings. That research and capability are rarely available in experimental facilities that use water as the preferred fluid medium. Our group has successfully employed a Makita-style active grid turbulence generator that is comprised of ten rotating shafts with a dedicated stepper motor to control each shaft. A total of sixty rotating winglets rotate using various control protocols to produce controlled and elevated levels of free-stream turbulence. For the current experimental campaign, we vary the shaft angular frequency ranging from 0.25 to 3.0Hz to vary the vane Rossby number; the free stream velocities are also varied between 0.10m/s-0.83m/s to vary the mesh Reynolds number. Besides, the winglet blockage was varied by altering the size and solidity of the winglets. We will present the results of our experiments by presenting flow statistics such as turbulence intensity, Taylor Reynolds number, flow anisotropy, and integral length scale for the various cases tested. A comparison will be also be done with wind-tunnels tests over the same parameter range.

Funding acknowledgment: The authors thank the US National Science Foundation for financial support for this project (Award #1706358, Fluid Dynamics Program).

About Christopher Ruhl   

Chris Ruhl is currently in his second year of his PhD program in the Department of Mechanical Engineering and Mechanics. He obtained his Bachelor of Science degree in Mechanical Engineering from Lehigh in 2016 and his Master of Engineering degree in Technical Entrepreneurship from Lehigh in 2017. Upon completion of his masters, Chris worked for a software company in New York City from 2017-2019, before transitioning to his role as a civilian mechanical engineer for the U.S. Army in 2019 at the Aberdeen Proving Grounds. Ultimately, Chris decided to return to his alma mater in Fall 2019 to begin the pursuit of his PhD in mechanical engineering. Chris’s current studies focus on the production and characterization of turbulent flow using an active grid turbulence generator as well as turbulent flow interactions with tidal stream turbine devices. Chris was a member of the Lehigh University Football team from 2012-2016.