Date of Award:
Master of Science (MS)
Mechanical and Aerospace Engineering
Solving the problems of increasing highway fuel efficiency, throwing a better curve ball, and preventing an aircraft from stalling all have a common thread: controlling flow separation. Defined by the fast moving flow around an object detaching from the object, flow separation has implications for a broad number of engineering fields. Research regarding flow separation control has led to the understanding that the easiest method for delaying flow separation for a given shape is to vary how turbulent the flow around the object is. Varying this turbulence around an object may be achieved through various methods including changing the spin or surface roughness of the object. While spinning the object is seemingly straightforward, there are a myriad of options for varying the surface roughness. Further, how spin and surface features relate to each other is less understood. As a result, this study sought to understand how yet unexplored surface roughness patterns and spin interact as they relate to the boundary layer separation over a sphere. To identify where separation occurred, small particles were added to still air and illuminated in a thin sheet by a laser. Spheres were launched through the air and a digital camera captured images of the particles as the sphere passed through the field of view. These images allowed us to identify where the flow had separated. These separation points across a number of sphere roughness types and spin rates were mapped and compared to the known lift and drag on the spheres. Results show relationships between flow separation and lift/drag, demonstrating the potential for the surface roughness pattern to control the sphere aerodynamics.
Elliott, Jack C., "The Influence of Surface Roughness Frequency on Rotating Sphere Aerodynamics" (2023). All Graduate Theses and Dissertations. 8792.
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