Increasing Helicity towards Dynamo Action with Rough Boundary Spherical Couette Flows
| dc.contributor.advisor | Lathrop, Daniel P | en_US |
| dc.contributor.author | Rojas, Ruben | en_US |
| dc.contributor.department | Physics | en_US |
| dc.contributor.publisher | Digital Repository at the University of Maryland | en_US |
| dc.contributor.publisher | University of Maryland (College Park, Md.) | en_US |
| dc.date.accessioned | 2023-03-29T05:30:17Z | |
| dc.date.available | 2023-03-29T05:30:17Z | |
| dc.date.issued | 2022 | en_US |
| dc.description.abstract | The dynamo action is the process through which a magnetic field is amplified and sustained by electrically conductive flows. Galaxies, stars and planets, all exhibit magnetic field amplification by their conductive constituents. For the Earth in particular, the magnetic field is generated due to flows of conductive material in its outer core. At the University of Maryland, our Three-meter diameter spherical Couette experiment uses liquid sodium between concentric spheres to mimic some of these dynamics, giving insight into these natural phenomena. Numerical studies of Finke and Tilgner (Phys. Rev. E, 86:016310, 2012) suggest a reduction in the threshold for dynamo action when a rough inner sphere was modeled by increasing the poloidal flows with respect to the zonal flows and hence increasing helicity. The baffles change the nature of the boundary layer from a shear dominated to a pressure dominated one, having effects on the angular momentum injection. We present results on a hydrodynamics model of 40-cm diameter spherical Couette flow filled with water, where torque and velocimetry measurements were performed to test the effects of different baffle configurations. The selected design was then installed in the 3-m experiment. In order to do that, the biggest liquid sodium draining operation in the history of the lab was executed. Twelve tons of liquid sodium were safely drained in a 2 hours operation. With the experiment assembled back and fully operational, we performed magnetic field amplification measurements as a function of the different experimental parameters including Reynolds and Rossby numbers. Thanks to recent studies in the hydrodynamic scale model, we can bring a better insight into these results. Torque limitations in the inner motor allowed us to inject only 4 times the available power; however, amplifications of more than 2 times the internal and external magnetic fields with respect to the no-baffle case was registered. These results, together with time-dependent analysis, suggest that a dynamo action is closer than before; showing the effect of the new baffles design in generating more efficient flows for magnetic field amplification. We are optimistic about new short-term measurement in new locations of the parameter space, and about the rich variety of unexplored dynamics that this novel experiment has the potential to reach. These setups constitute the first experimental explorations, in both hydrodynamics and magnetohydrodynamics, of rough boundary spherical Couette flows as laboratory candidates for successful Earth-like dynamo action. | en_US |
| dc.identifier | https://doi.org/10.13016/dkkw-jvpp | |
| dc.identifier.uri | http://hdl.handle.net/1903/29753 | |
| dc.language.iso | en | en_US |
| dc.subject.pqcontrolled | Fluid mechanics | en_US |
| dc.subject.pqcontrolled | Geophysics | en_US |
| dc.subject.pqcontrolled | Plasma physics | en_US |
| dc.subject.pquncontrolled | Dynamo | en_US |
| dc.subject.pquncontrolled | Magnetohydrodynamics | en_US |
| dc.subject.pquncontrolled | Spherical Couette | en_US |
| dc.subject.pquncontrolled | Turbulence | en_US |
| dc.title | Increasing Helicity towards Dynamo Action with Rough Boundary Spherical Couette Flows | en_US |
| dc.type | Dissertation | en_US |
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