Dissertation: "Numerical and Experimental Study on the Ability of Dynamic Roughness to Alter the
Development of a Leading Edge Vortex"
Thesis: "Pressure Deflection Behavior of Candidate Materials for Morphing Wings"
While working as a Research Assistant Professor, the department advertised a teaching track position. I was fortunate enough to be offered the position and am excited to work in this role. Although my primary responsibility is teaching undergraduate courses, I still can participate in a variety of research that enhances my teaching ability. Recently, I have predominantly taught aerodynamics oriented courses, including Incompressible Aerodynamics, Compressible Aerodynamics, and Introduction to Aerospace Engineering.
I continue to work on research projects dealing with unsteady aerodynamics, computational fluid dynamics, and unmanned aerial systems. I’ve recently become involved with an NSF education-based research project that I am honored and excited to be a member.
My background in unsteady aerodynamics led me to work on a project dealing with trajectory and orientation prediction of unstable aerodynamic bodies. As part of this research team, I aided in the development of an outdoor research facility. This facility provides the ability to record projectile launches using multiple synchronized high-speed cameras, as well as a 70 camera VICON motion capture system. The goal is to statistically validate models as well as dive into the physics that cause the motions captured during test flights.
I also started an additional project dealing with the flow and thermal properties of submerged tubing. My primary task is CFD analysis of various tubing and their components at different ambient and flow conditions. The goal is to make the fluid delivery system more efficient in terms of pressure drop across the system, as well as to reduce heat loss.
I also taught classes as needed, including Introduction to Aerospace Engineering, Statics, and Thermal and Fluids Laboratory.
Upon graduation, I was hired as a Visiting Scholar which then transitioned into a Postdoctoral Fellowship. In this role, I extended my active flow control studies into the area of projectile maneuverability. The experimental analysis was conducted using particle image velocimetry (PIV) to visualize the flow field around 40mm mortar rounds. Static and dynamic roughness elements were added to document their effect on the flow field. Although there was an effect, results were not conclusive on its ability to potentially maneuver such an object.
I also was able to continue teaching as needed by the department in this role. I taught several classes, including Fluid Mechanics, Computational Fluid Dynamics, and Thermodynamics.
The goal of my dissertation work was to evaluate the application of dynamic roughness to rapidly pitching airfoils. Dynamic roughness has previously been used to computational and experimentally eliminate the laminar separation bubble near the leading edge of an airfoil at various angles of attack. The new application involves the delay of the dynamic stall phenomenon. Dynamic stall is a condition that occurs on airfoils undergoing relatively rapid pitching maneuvers, or airfoils that are impulsively started at a large angle of attack. In these cases, the airfoil is able to continue to produce lift beyond the static stall angle of attack.
A consequence of dynamic stall is the development of a leading-edge or dynamic stall vortex. This vortex helps to sustain lift, but once the vortex sheds downstream there is an abrupt loss of lift, increase in drag, and change in pitching moment. I was able to show computationally and experimentally that dynamic roughness can delay the formation of the leading-edge vortex. I used particle image velocimetry (PIV) to visualize the flow field around the pitching airfoil and the commercial CFD code Fluent in this research. Using macros and user-defined functions I was able to develop additional code to simulate the pitch-up maneuver, as well as surface displacement to mimic dynamic roughness. It is hoped dynamic roughness will have less energy consumption than other active flow control techniques such as plasma or blowing/suction.
It was also during this time that I started teaching as a graduate student. My first class was Fluid Mechanics.
Working on the Resilient Tunnel Project was a challenging but rewarding experience. The goal was to develop an inflatable structure that could act as a flood mitigation barrier in subterranean transit tunnels. Our multidisciplinary team consisted of faculty and students from the Mechanical and Aerospace Engineering Department, Civil and Environmental Engineering Department, and the LANE Computer Science and Computer Engineering Department.
My primary role was to design, development, and implement systems dealing with fluid storage, transmission, and sensing. I developed data acquisition hardware and software techniques to record flowrate, pressure, and displacement. While working on this project, we transitioned from small 3-foot scaled experiments to full scale and full pressure subway mockups. The full-scale experiments required designing and implementing pumps and plumbing to safely deliver water at over 3000 GPM. I also had the honor to work with industry and government partners such as ILC Dover, Department of Homeland Security, and the Pacific Northwest National Laboratory. Some additional info can be seen by accessing the links below.
My MS research investigated the behavior of various materials under biaxial load conditions for potential use on the surface of a morphing wing. In order to test different types of flexible materials, I designed and fabricated a bulge test apparatus. This device is a pressure vessel with a clamping end that allows material to be securely installed. Upon pressurization material displaces, the profile of the displacement is measured using a traversing optical range. This profile measurement allows biaxial stress calculations.
The results showed a combination of woven and rubber based materials would provide excellent conformability while providing the balance between strength and flexibility required by morphing structures.
While at NIOSH, I worked in the Surveillance and Field Investigations Branch (SFIB), which is within the Division of Safety Research (DSR). I worked on a project whose goal was to investigate highway construction safety hazards, particularly the hazard of workers being struck by construction vehicles or equipment. Our group was also tasked with developing and evaluating interventions that would reduce this risk to highway construction workers.
To identify high-risk areas around construction equipment, I collected and digitized Construction Equipment Visibility (Blind Area) Diagrams for various types of vehicles and equipment used on highway construction sites. I subsequently developed a NIOSH website to host these diagrams for public access, https://www.cdc.gov/niosh/topics/highwayworkzones/bad/imagelookup.html . The investigations used GPS location trackers to track worker movement throughout the day, in addition to construction equipment. Along with my colleagues, I helped develop programming that would use the GPS data from the construction worker and that of the construction equipment to identify the number of times and duration in which a worker was considered in a high-risk region.
Interventions developed to reduce risk included proximity warning devices, backup cameras, and Internal Traffic Control Plans (ITCP). I was particularly tasked with fabricating hardware and installing the proximity warning devices and backup cameras on dump trucks.
"I wish every engineering professor was like this, very straight-forward, easy to understand, and gave a good conceptual explanation to things."
"All material was presented in a clear manner and was easily understood. Examples always reinforced newly presented material."
"Dr. Griffin is an awesome professor!! He connects very well with all of his students while maintaining a structured and organized class."
"He was such a great teacher! He was so helpful and helped me realize why I wanted to be an engineer!"
"He did a good job explaining the concepts during lecture, and was easy to understand and follow. He was very friendly and approachable if anyone needed help outside of class. He did his best to make sure that students understood the material. Overall, a very good professor."
Griffin, C. D., Huebsch, W. W., Rothmayer, A. P., and Wilhelm, J. P., "Numerical and Experimental Study on the Ability
of Dynamic Roughness to Alter the Development of a Leading Edge Vortex," Fluid Mechanics: Open Access, Vol. 3,
No. 2, (2016).
Griffin, C. D., Browning, P. H., Hamburg, S. D., Cox, J., Katzner, E. E., Katzner, T. E., and Huebsch, W. W.,
"Free Flight Observations and Aerodynamic Analysis for Biologically-Inspired Optimization," AIAA Paper 2017-0501,
55th AIAA Aerospace Sciences Meeting, SciTech Forum, January 9-13 2017, Grapevine, TX.
Griffin, C. D. and Huebsch, W. W., "Numerical and Experimental Study on the Ability of Dynamic Roughness to Alter
the Development of a Leading Edge Vortex," AIAA Paper 2014-2047, 32nd AIAA Applied Aerodynamics Conference,
AIAA Aviation and Aeronautics Forum and Exposition, June 16-20 2014, Atlanta, GA.
Griffin, C. D. and Huebsch, W. W., "Development and Progress of Biologically-Inspired Aerodynamics Research at
West Virginia University," Aerospace Systems Directorate - US Air Force Research Lab, July 8 2015, Wright-Patterson
Air Force Base, Dayton, OH.
Griffin, C. D. and Huebsch, W. W., Dynamic Roughness as a Means for Aerodynamic Flow Control. Poster presented at:
Linking Innovation Industry & Commercialization; November 2012; Morgantown, WV.
Munson, Bruce R., Rothmayer, Alric P., Okiishi, Theodore H., Huebsch, Wade W., Fundamentals of
Fluid Mechanics. 7th ed. Hoboken, NJ; John Wiley & Sons, 2013.
Young, Donald F., Munson, Bruce R., Okiishi, Theodore H., Huebsch, Wade W., A Brief Introduction to
Fluid Mechanics. 5th ed. Hoboken, NJ; John Wiley & Sons, 2011.