Turbulence in Superfluid 4-He Films around Substrate Defects

This thesis seeks to help explain dissipation observed in third sound Superfluid 4He by the Quantum Fluids Group at Wesleyan. Turbulence is a common hypothesis for these types of dissipation; however, it is not well understood how vortices form and nucleate in Superfluid. This project examines possible vortex formation conditions around surface defects: obstructions and bumps. We have solved for the flow fields of vortex pairs around defects, found the energy costs to vortex pair nucleation around these defects, and shown that energy cost for pair nucleation is lower for larger defects in higher velocities. Along with microscopic measurements of superfluid resonator surface defects, this model should be able to confirm whether or not observed dissipation is resulting from vortex pair formation around surface defects. Acknowledgements I would like to thank the Wesleyan University Physics department for educating me on the mathematical methods for understanding the universe that I have come to love so dearly. I would like to especially thank Professor Fred Ellis for dedicating so much of his time to educating me and supporting me through this project, as well as for his physics and general life advice that has helped me make sense of a very confusing world. He has helped me to cultivate a sense of mathematical wonder for the world around me that I wish everyone could feel. I would also like to thank Professor Greg Voth for teaching in an exceptionally clear, interesting manner that was especially effective for my learning style, as well as Professor Bryan Stewart, for helping me to decide that Wesleyan physics was the program for me. I would also like to extend my gratitude to the rapper GZA, who has repeatedly shown me the value of understanding the physical world as a way to understand oneself and one’s place within it through his music. Table of